THE UNIVERSITY OF NEW SOUTH WALES Thesis/Dissertation Sheet

Surname or Family name : Adiyanto

First name : Farid Hendro Other name/s : -

Abbreviation for degree as given in the University calendar : ME

School : Surveying and Spatial Information Systems Faculty : Engineering

Title:

Temporary CORS Network for Land Reconstruction in Aceh, Sumatra.

Abstract 350 words maximum: (PLEASE TYPE)

Using CORS networks for land reconstruction after earthquakes and tsunamis is challenging due to the limited infrastructure remaining after the event. Normally, CORS networi

This thesis tries to investigate the utilizing of temporary CORS network approach; that is using some higher order stations as base station monuments, setting up a temporary CORS networic over a small region and when operations are completed, packing up the system and moving to an adjacent network of high order monuments which comprise a new temporary CORS networks. Due to logistical considerations during the organization of this project, real-time communications were not used in Aceh and only GPS data was logged in the field. Reference stations logged 24 hours of GPS data and were processed using the free online service from AUSPOS. These coordinates are then used in a post- processed simulation mode using the Leica SpiderNet software.

As a comparison, there is a similar simulation that has been conducted using the well established network RTK GPS infrastructure that belongs to Singapore Land Authority (SLA) in Singapore. The Aceh data simulation showed that the network RTK suffered from bad network geometry and lack of the common satellite number. On the other hand, the SLA data struggled in network ambiguity resolution due to ionospheric activity in equatorial region. Overall, single based and network RTK GPS is still reliable if it is used in land reconstruction in equatorial region. But it has to give more attention in the extending range and high density of reference stations.

Declaration relating to disposition of project thesis/dissertation

I hereby grant to the University of New South Wales or its agents the right to archive and to make available my thesis or dissertation in whole or in part in the University libraries in all fonns of media, now or here after known, subject to the provisions of the Copyright Act 1968.1 retain all property rights, such as patent rights. I also retain the right to use in future wori^s (such as articles or books) all or part of this thesis or dissertation.

I also authorise University Microfilms to use the 350 word abstract of my thesis in Dissertation Abstracts Intemational (this is applicable to doctoral theses only).

20 February 2010

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THIS SHEET IS TO BE GLUED TO THE INSIDE FRONT COVER OF THE THESIS Temporary GPS CORS Network for Land Reconstruction in Acefi, Sumatra

By Farid Hendro Adiyanto

A thesis submitted in partial fulfilment for the degree of Master of Engineering

School of Surveying and Spatial Information Systems The University of New South Wales Australia

2010 COPYRIGHT STATEMENT

'I hereby grant the University of New South Wales or its agents the right to archive and to make available my thesis or dissertation in whole or part in the University libraries in all forms of media, now or here after known, subject to the provisions of the Copyright Act 1968. I retain all proprietary rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part of this thesis or dissertation. I also authorise University Microfilms to use the 350 word abstract of my thesis in Dissertation Abstract International (this is applicable to doctoral theses only). I have either used no substantial portions of copyright material in my thesis or I have obtained permission to use copyright material; where permission has not been granted I have applied/will apply for a partial restriction of the digital copy of my thesis or dissertation.'

Signed :

Date : 20 February 2010

AUTHENTICITY STATEMENT

'I certify that the Library deposit digital copy is a direct equivalent of the final officially approved version of my thesis. No emendation of content has occurred and if there are any minor variations in formatting, they are the result of the conversion to digital format.'

Signed :

Date : 20 February 2010 ORIGINALITY STATEMENT

'I hereby declare that this submission is my own work and to the best of my knowledge it contains no materials previously published or written by another person, or substantial proportions of material which have been accepted for the award of any other degree or diploma at UNSW or any other educational institution, except where due acknowledgement is made in the thesis. Any contribution made to the research by others, with whom I have worked at UNSW or elsewhere, is explicitly acknowledged in the thesis. I also declare that the intellectual content of this thesis is the product of my own work, except to the extent that assistance from others in the project's design and conception or in style, presentation and linguistic expression is acknowledged.'

Signed :

Date : 20 February 2010 ABSTRACT

ABSTRACT

Using CORS networks for land reconstruction after earthquakes and tsunamis is challenging due to the limited infrastructure remaining after the event. Normally, CORS networks are set up in well established cities or regions with developed infrastructure and utilities. The functionality of a CORS approach is suitable to re-establish more than 10,000 land parcels in Aceh affected by the tsunami, but can this method still be useful with limited infrastructure? Also, can a CORS network feasibly re-establish cadastral land parcel boundaries previously based on bearings and distances using coordinates? This is a very crucial problem as often no survey marks exist to re-establish property boundaries. CORS networks can provide an external infrastructure allowing the identification of existing survey marks and the lay out of new and existing parcels for a large number of independent users. Using sophisticated network RTK algorithms, larger inter- receiver distances allow CORS networks to cover large areas with a minimal number of reference stations reducing the cost of operations. Also in equatorial regions, such as Aceh, where ionospheric activity is expected to be higher, a slightly denser array of CORS stations should ensure more reliable initialization.

This thesis tries to investigate the utilisation of a temporary CORS network approach; that is using some higher order stations as base station monuments, setting up a temporary CORS network over a small region and when operations are comple.ted, packing up the system and moving to an adjacent network of high order monuments which comprise a new temporary CORS network. Due to logistical considerations during the organization of this project, real-time communications were not used in Aceh and only GPS data was logged in the field. Reference stations logged 24 hours of GPS data and were processed using the free online service from AUSPOS. These coordinates are then used in a post- processed simulation mode using the Leica SpiderNet software. ABSTRACT

As a comparison, a similar simulation was conducted using the well established network RTK GPS infrastructure run by the Singapore Land Authority (SLA) in Singapore. The Aceh data simulation showed that the network RTK suffered from bad network geometry and lack of common satellites in the solution. The SLA data showed better results but still struggled with network ambiguity resolution due to the ionospheric activity in the equatorial region. Overall, the network RTK simulation did not prove significantly more reliable than single based RTK (at this stage) due largely to higher ionospheric effects creating noisy signals which either precluded the use of satellites in the solution or disallowed fixed initialisation. This problem could be overcome if network RTK algorithms could be "tuned" for higher noise environments. This intermittent unreliability also reinforces the need for a best practice user guideline to be drafted to assist surveyors and other users when using GPS for legal surveys in Indonesia.

Ill ACKNOWLEDGMENT

ACKNOWLEDGMENT

In this acknowledgment, I would like to express my sincere gratitude to my supervisor, Dr. Craig Roberts who provided invaluable assistance, guidance, and constructive support throughout the years of my study and thesis writing with full patience and for my co-supervisor. Dr. Bruce Harvey who gave me statistic surveying materials. I have learned and gained wonderful experiences while undertaking this project until the completion. I admire their high dedications in supporting the students.

My special thanks to Prof. Chris Rizos who provided a chance to join the SNAP Lab, a great research group in the world and Ir. Wenny Rusmawar Idrus, Deputy of Surveying and Mapping Indonesian National Agency to take temporary CORS network project in Aceh and special support during the project. Special thanks also go to Thomas Yan who has assisted me with all network RTK GPS material, processing, simulation, fruitful discussion, technical advise and sharing knowledge. Also, I would like to thank to all Leica Geosystem team (Joel Van Crannenbroeck, Peter Maier, Leinhart Troyer, Neil Ashcroft, Busroni Arief Yanto, Adhityo Nugroho) for their great support, interesting discussion and assistance during the fieldwork and data processing.

The next special thanks are for my best colleagues in Singapore Land Authority (SLA) particularly to Mr. Poh Weng Wong, Mr. Victor Khoo and Mr. Derrick Tan for providing the network RTK GPS data from Singapore network. Also, I would like to thanks to all my colleagues at the SNAP Lab especially room 413B, Fabrizio, Sana, Omar, Ishrat, Faisal, Hong Joo and all postgraduate research students in School of Surveying and Spatial Information Systems, for their help, useful discussions, and friendship that we enjoy much. The last thanks to the school, I would also like to thank all the staff members at the School of Surveying and Spatial Information Systems for their help and cooperation that makes being a graduate student in this school much easier. ACKNOWLEDGMENT

The next my best special thanks also go to National Land Agency RALAS project team in Aceh who have assisted me in fieldwork project in Banda Aceh, especially for Sudarman Hardjasaputra, Arief Suhattanto, Arli Buchari, Karnanto Hendra, Muji, Andi, Usep and Ir. Bambang Ardiantoro M.Sc and Ir. Freddy from the Directorate of Surveying and Mapping Indonesian Land Agency for all instruments support. I also acknowledge The Australian Agency for International Development (AusAID), especially for Australian Partnership Scholarship (APS) for providing the scholarship for my study and fieldwork travel grant.

Finally, my best thanks to my beloved wife Yayah, my mother and father, my mother and father in law also to all my brothers and sisters who always give great advice, support during my study, and to my extraordinary friends in Sydney and Indonesia, for their great love and support. I dedicate this thesis to them. PUBLICATIONS

PUBLICATIONS

Author

Adiyanto. F. H., Roberts. C. Temporary CORS Network for Land Reconstruction in Aceh, Sumatera. IGNSS Conference 2007, University of New South Wales, Sydney-Australia, 4-6 December 2007.

Adiyanto. F. H., Nugroho. A. S. Development of the Idea of CORS Network in Indonesia (in Bahasa). Annual Conference, Indonesian Surveyor Association, Jakarta, Indonesia, October 2007.

Adiyanto. F. H. Study of Using RTK GPS and CORS Network for Urban Cadastral Surveying (in Bahasa), Annual Conference, Indonesian Surveyor Association, Balikpapan East Kalimantan, October 2006

Adiyanto. F. H., Arsana. I. M. A. Forensic Cadastre for Natural Disasters, Opinion and Editorial, the Jakarta Post, October 2006.

Adiyanto. F. H. Land Readjustment after Natural Hazards. Opinion and Editorial, the Jakarta Post, August 2006

Co-author

Roberts. C., Yan. T., Adiyanto. F. H., Kinlyside. D., McElroy. S., Jones. G. Centimeters across Sydney: First Results from the Sydnet CORS Network. SSC2007 Spatial Science Institute, Biennial International Conference, Hobart Tasmania, 14-18 May 2007 TABLE OF CONTENTS

TABLE OF CONTENTS

Abstract ii Acknowledgement iv Publications vi Table of Contents vii Abbreviations x List of Figure xiv List of Table xvii Chapter 1 Introduction 1 1.1. Statement of the Topic 1 1.2. Scope of the Research 8 1.3. Research Aim 9 1.4. Contribution to Research 10 1.5. Tentative Thesis Chapter 10 Chapter 2 Boxing Day Earthquake and Tsunami in Aceh 12 2.1. Impact in Cadastral and Land Administration System 15 2.2. RALAS (Reconstruction of Aceh Land Administration System) Project 18 2.3. Surveying and Mapping 20 2.4. Rebuilding the Cadastral System after the Shock 22 Chapter 3 GPS for Cadastral Surveying in Indonesia 25 3.1. Cadastral in Indonesia, an Overview 25 3.2. GPS in Cadastral Surveying 30 3.3. Geodetic Infrastructure 32 3.4. Using GPS for Land Reconstruction in Aceh 38

Vll TABLE OF CONTENTS

Chapter 4 Continuously Operating Reference Station (CORS) Network 43 4.1. History of CORS Network 43 4.2. The Early Development of CORS Network in Indonesia 46 4.3. CORS Network Definition 49 4.3.1. Hardware Configuration 51 4.3.2. Site Configuration 52 4.3.3. Data Management 54 4.4. Network RTK Concept 55 4.5. Network Communication Concept 56 4.5.1. Virtual Reference Station 56 4.5.2. Area Correction Parameter 58 4.5.3. Master Auxiliary Concept 60 4.6. Communication Condition in Aceh 62 Chapter 5 Trophospheric and Ionospheric Delay 67 5.1. Troposphere 68 5.2. Ionosphere 72 5.2.1. Ionosphere Free Combination 78 5.2.2. Narrow-Lane Combination 80 5.3. TEC Map 81 5.4. Special Behavior of Ionosphere and its Visualization in Equator 87 5.5. Geomagnetic Storm 89 Chapter 6 Fieldwork in Aceh 92 6.1. Temporary CORS Network for Land Reconstruction 93 6.2. Temporary CORS Network Fieldwork 95 6.3. Survey Planning and Assessment 96 6.4. Site Selection and Skyplot Analysis 97 6.5. Common Satellite in Survey Planning 102 6.6. Problem Identification 103

Vlll TABLE OF CONTENTS

6.7. GPS Static Survey 104 Chapter 7 Network RTK Simulation 109 7.1. Network RTK Simulation in Aceh 109 7.1.1. Reference Points Computation 109 7.1.2. GPS Static Processing 112 7.1.3. Network RTK GPS Simulation 113 7.1.4. Baseline Result Epoch by Epoch Processing 118 7.1.5. Point Result Epoch by Epoch Processing 120 7.1.6. Conmion Satellite Requirement 123 7.1.7. Network Strength 125 7.2. Network RTK Simulation Using SiReNT 126 7.2.1. Singapore Satellite Positioning Reference Network (SiReNT) 127 7.2.2. Simulation Method 128 7.2.3. Network Correction Processing 128 7.2.4. Baseline Result Epoch by Epoch Processing 130 7.2.5. Point Result Epoch by Epoch Processing 132 7.2.6. Common Satellite Requirement 135 7.2.7. LI Processing Test 135 7.2.9. Cross Correlation 137 Chapter 8 Conclusion and Recommendation 140 8.1. Conclusion 140 8.2. Recommendation 144 References 147 Appendix A 159 Appendix B 183 ABBREVIATION

ABBREVIATIONS

AIPRD Australia Indonesia Partnership for Reconstruction and Development AusAid Australian Government's Overseas Aid Program AUSLIG Australian Surveying and Land Information Group AUSPOS AUSLIG Online GPS Processing System

B

Bakosurtanal Badan Koordinasi Survey dan Pemetaan Nasional BKG Bundesamt fur Kartographie und Geodäsie BPN Badan Pertanahan Nasional BRR Badan Rekonsruksi dan Rehabilitasi BTS Base Transceiver Station

C/A Coarse Acquisition CDMA Code Division Multiple Access CF Compact Flash CORS Continuously Operating Reference Station CPU Client Premises Unit

D

DOP Dilution of Precision

FC Fiscal Cadastre FIG Federation Internationale des Geometres FKP Flachen Korrektur Parameter FM Frequency Modulation

3G Generation GDA94 Geodetic Datum of Australia 94 GDOP Geometry Dilution of Position GHz Giga Hertz Glonass Global'naya Navigatsionnaya Sputnikova Sistema GNSS Global Navigation Satellite System ABBREVIATION

GPS Global Positioning System GPRS General Packet Radio Service GSM Global System for Mobile Communications GULFNet Gulf Network

H

HSDPA High Speed Downlink Packet Access

I

ID74 Indonesian Datum 74 ID95 Indonesian Datum 95 IGS International GNSS Service IP Internet Protocol IOC Initial Operational Capability lONEX Ionosphere Map Exchange ITRF International Terrestrial Reference Frame

J

JPL Jet Propulsion Laboratory

L

LIPI Lembaga Ilmu Pengetahuan Indonesia LGO Leica Geo Office

M

MAC Master Auxiliary Concept MB Mega Byte Mbps Mega Byte per Second MDTFANS Multi-Donors Trust Fund for Aceh and North Sumatra

N

NASA National Aeronautics and Space Administration NGDC National Geophysical Data Centre NGS National Geodetic Survey NGO Non Government Organization NMBA National Marine Electronics Association NOAA National Oceanic and Atmospheric Administration NRTK Network RTK ABBREVIATION

PBB Pajak Bumi dan Bangunan PMNA Peraturan Menteri Negara Agraria PPS Precise Positioning Service PRN Pseudo Random Noise

Q QC Quality Control R RALAS Reconstruction of Aceh Land Administration System RC Recht Cadastre RINEX Receiver Independent Exchange Format RTCM Radio Technical Commission for Maritime Service RTK Real Time Kinematic

SAPOS Satelliten Positionierungsdients SLA Singapore Land Authority VRS Virtual Reference Station SWEPOS Sweden Positioning SuGAr Sumatran GPS Array SydNet Sydney Network SIMSRN Singapore Integrated Multiple Reference Station Network SiReNT Singapore Satellite Positioning Reference Network SPS Standard Positioning Service

TEC Total Electron Content TM3 Transverse Mercator 3 Degree U UHF Ultra High Frequency UNAVCO UNSW University of New South Wales UPS Uninterruptible Power Supply USGS United States Geological Survey UTC Coordinated Universal Time UTM Universal Transverse Mercator UV Ultra Violet

Xll ABBREVIATION

VHF Very High Frequency VSAT Very Small Aperture Terminal

W

WBA Wireless Broadband Access WGS84 World Geodetic System 84 WiMAX Wifi Max

Xlll LIST OF FIGURE

LIST OF FIGURE

Fig. 1.1. GPS system segment 3 Fig. 1.2. Double differencing 5 Fig. 1.3. Real Time Kinematic GPS 5 Fig. 2.1. The epicenter and affected area 13 Fig. 2.2. Ground displacement magnitude 14 Fig. 2.3. The physical land books that in poor condition after the tsunami 16 Fig. 2.4. Manually identified land parcels due to a lack of cadastral maps (left picture). Loss of land parcel boundaries (right picture) 17 Fig. 2.5. Location of satellite imagery mapping 22 Fig. 3.1. Indonesian archipelago, courtesy Google Earth 27 Fig. 3.2. Current status of cadastral and spatial databases in Indonesia 28 Fig. 3.3. Indonesian GPS tracking stations between the other stations in the world 34 Fig. 3.4. SydNet permanent stations across Sydney 37 Fig. 3.5. GPS permanent stations 38 Fig. 3.6. GPS included in parcel boundary reconstruction process 40 Fig. 3.7. Parcel boundaries survey with GPS and Total Station 41 Fig. 4.1. Permanent GPS stations in Indonesia 47 Fig. 4.2. Sumatran GPS Array 48 Fig. 4.3. VRS concept 58 Fig. 4.4. FKP Correction Symbolization 59 Fig. 4.5. Cell and cluster system 60 Fig. 4.6. MAC Concept 61 Fig. 4.7. The configuration of Base Transceiver Station (BTS) towers and wireless points in the Banda Aceh region plotted in Google Earth 64 LIST OF FIGURE

Fig. 5.1. Atmosphere layers 68 Fig. 5.2. Sun Spot Number variations 73 Fig. 5.3. The Ionosphere layers courtesy University Corporation for Atmospheric Research 74 Fig. 5.4. 3D Ionosphere Model 75 Fig. 5.5. TEC Map in 02.00 UTC 82 Fig. 5.6. TEC Map in 04.00 UTC 83 Fig. 5.7. TEC Map in 06.00 UTC 84 Fig. 5.8. TEC Map in 08.00 UTC 85 Fig. 5.9. TEC Map in 10.00 UTC 86 Fig. 5.10. TEC Map in 12.00 UTC 87 Fig. 5.11. A false color image of ultraviolet light in ionosphere that encircles the Earth 88 Fig. 5.12. Kp Index in the day of survey, 7 May 2007 90 Fig. 6.1. Leica GPS System 500 and System 1200 95 Fig. 6.2. Flow chart for the fieldwork and data processing 96 Fig. 6.3. UPS and accumulator 97 Fig. 6.4. Skyplot diagram for Khaju site. Cut off angle 15°, 9 am-7 pm 100 Fig. 6.5. DOP estimation for Khaju site. Cut off angle 15°, 9 am-7pm 101 Fig. 6.6. The satellite availability for Khaju site 102 Fig. 6.7. Compact flash and its adapter 104 Fig. 6.8. Reference Points (yellow stars) and rover survey marks (blue squares) overlaid on Google Earth and the damaged coastline 106 Fig. 6.9. Pictures of Reference Stations, Khaju, Lhoknga and GH 107 Fig. 7.1. Nearest IGS stations for reference points data processing 111 Fig. 7.2. Cluster and cell based on three reference stations 114 Fig. 7.3. Baseline GH-KNWL, first session 118 Fig. 7.4. Baseline GH-KNWL, second session 119 Fig. 7.5. Baseline GH-KNWL, third session 119 Fig. 7.6 Easting on KNWL, first session 120 LIST OF FIGURE

Fig. 7.7. Northing on KNWL, first session 121 Fig. 7.8 Easting on KNWL, second session. 121 Fig. 7.9. Northing on KNWL, second session 122 Fig. 7.10. Easting on KNWL, third session 122 Fig. 7.11. Northing on KNWL, third session 123 Fig. 7.12. SiReNT reference stations 127 Fig. 7.13. Baseline SKEP-15399, first session 130 Fig. 7.14. Baseline SKEP-15399, second session 131 Fig. 7.15. Easting on 15399, first session 132 Fig. 7.16. Northing on 15399, first session 133 Fig. 7.17. Easting on 15399, second session 133 Fig. 7.18. Northing on 15399, second session 134 Fig. 7.19. Baseline comparison from LI and L1+L2 processing in point 15399 first session 136 Fig. 7.20. Baseline error from LI and L1+L2 processing in point 15399 first session 136 LIST OF TABLE

LIST OF TABLE

Table 2.1. The relationship between land parcels, land title holder, land certificate and supporting documents after the earthquake and tsunami 18 Table 4.1. Permanent GPS stations in Indonesia 46 Table 4.2. Suitable GPS positioning methods for certain survey applications 50 Table 5.1. Classification of Kp Index Value 89 Table 6.1. Assessment of reference stations 98 Table 7.1. Reference points coordinate result 111 Table 7.2. Reference points coordinate result from LGO processing 112 Table 7.3. Result of the first session comparing network RTK (NRTK) with static processing for five rover points from the GH base station 115 Table 7.4. Result of the second session comparing network RTK (NRTK) with static processing for five rover points from the GH base station 116 Table 7.5. Result of the third session comparing network RTK (NRTK) with static processing for five rover points from the GH base station 117 Table 7.6. Common satellites in the first session 124 Table 7.7. Common satellites in the second session 124 Table 7.8. Common satellites in the third session 125 Table 7.9. Reference station coordinates 128 Table 7.10. Result of first and second session 129 Table 7.11. Common satellites in the first and second session 135 Table 7.12. Cross correlation in baseline SKEP-15399 138 Chapter 1 INTRODUCTION

Chapter 1 INTRODUCTION

1.1. Statement of the Topic

The Sumatra-Andaman earthquake (Mw 9.1) caused a huge displacement of the sea floor which in turn triggered the devastating tsunamis that struck countries surrounding the Indian Ocean such as Indonesia, India, Sri Lanka, Malaysia and Thailand (USGS, 2004). The worst affected was in Indonesia, particularly Sumatra Island. The affected areas were coastal regions particularly in Banda Aceh, Meulaboh and Simeuleu Island. The radius of the affected area was a few hundreds kilometres. The precise number of victims killed is still unknown. This natural disaster has had profound effects socially and economically on the daily lives of Acehnese people as well as causing enormous damage to infrastructure.

Land administration has also suffered from this tragedy. A large number of land parcels, boundary marks, cadastral maps and land documents have been lost. This will seriously impact land administration systems in Indonesia into the future (Benny et al, 2006). The Indonesian Government in collaboration with the World Bank deployed a land reconstruction project to provide land relief. The relief reconstruction was related to mapping and spatial planning. Re-locating and re- coordinating land parcel boundaries became more crucial because of the significant extent of land subsidence which occurred as a result of the earthquakes and tsunamis.

The Global Positioning System (GPS), in particular single based real-time kinematic (RTK), has been utilised for cadastral surveying in land reconstruction due to its high productivity (Busies, 2006). Strictly speaking, GPS for cadastral surveying is not specifically referred to in regulations as an approved method of survey for legal purposes in Indonesia. However, GPS has been used previously in Chapter 1 INTRODUCTION

Indonesia to support cadastral activities and given the unique circumstances in Aceh, it was considered a suitable methodology.

GPS is a mature technology that was a military project under the responsibility of the United States Department of Defence (DoD) (Hofmann-Wellenhof et al, 1998). This satellite system consists of three segments (see fig.I.l). The first segment is the space segment that nominally comprises 24 satellites (21 main satellites and +3 satellites as a reserve) then by March 2008 there are 32 satellites with 6 different orbital planes and 55° inclination to the equator. The second segment is the five control stations of the space segment. These control stations track the satellites, maintain the satellite clocks and compute and upload the orbits. The last segment is the user segment which since Initial Operational Capability (IOC) in 1995 has seen civilian users outnumber military users. Commercial, national and international civil users can access the GPS service. Generally, the advantages and services from GPS could be listed below:

1. 24 hours per day and operates in all weather. 2. Could be accessed worldwide. 3. Provide 3D high accuracy position (sub-centimetre). 4. Precise velocity and timing services. 5. Worldwide unlimited users (civilian and military). 6. The distance inter stations could be extended into hundreds or thousands kilometres. Chapter 1 INTRODUCTION

PLAWO) CONSiaLATiOft • 21 ACTIVE SATELLITES PLUS 3 SPAf^S IN 6 ORBíTS • EA&IAT0RBIT55DE«CESiriGLtíAT10N • ORaUSECSUALLY^ACEDARDUNDEOiATOR SPACE SEGMENT OOV#IL!NKC

USER segment-^KS MONITOR STATIG^IS CONTROL MASTER SEGMEMT coe^HOL STATION CCJPÍTROL SEGMENT SITE LOGftTlONS: WUNK STATIONS MASTER CONTRO. STATO^ - COLORADO SPRIMjS WONUC« STATIONS - CXXORADO SPRINGS. CO ASCBiSK^, DIEGO GM^IA. IFy W STATIONS - AS€£HSiOfl KWAJALEIti OIEGO GARCIA HAWAII KWAJALSN

Fig. LI. GPS system segment (Oncore, 2008).

The GPS satellites broadcast the L band signal at frequencies LI = 1575.42 MHz

and L2 = 1227.6 MHz with the carrier signal wavelength 19 and 24 cm (Leick,

2004). The signal was modulated with two pseudo-random noise (PRN) codes and

a navigation message. The civilian access (or coarse acquisition) C/A code is used

in the Standard Positioning Service (SPS) and the precise P-code is used for the

Precise Positioning Service (PPS).

Code measurements are used to compute the pseudorange between the GPS

satellite and GPS receiver. The pseudorange is computed from the transmission time from a broadcast signal to the user equipped with a GPS receiver multiplied by speed of light. Four simultaneous pseudorange measurements (ie observing to four satellites), provides a three dimensional position which is referred to as a Chapter 1 INTRODUCTION

GPS navigation solution. This method is not accurate for positioning due to non- synchronisation between the satellite and receiver clocks; hence the name pseudo range.

The precise method for positioning using GPS uses the carrier phase observation. This process combines simultaneous observations from two GPS receivers; differential positioning. The error sources for GPS observations are listed below:

1. Receiver clock error. 2. Satellite clock error. 3. Satellite orbit error. 4. Tropospheric and Ionospheric delay. 5. Multipath.

The International GNSS Service (IGS) have deployed GPS tracking stations globally to produce freely accessible precise orbit products for users. This precise orbit can eliminate the clock error as IGS claimed 2 cm in accuracy (Jonkman et al, 2005). However, for surveying applications, differencing the measurements by using two or more GPS receiver (double differencing) simultaneously and collecting many epochs of data effectively removes the clock error and improves the relative positioning (see fig. 1.2). The process for modelling the integers to resolve the unknown ambiguities of double difference carrier phase data is called ambiguity resolution. More complete explanation about GPS surveying concepts and methods can be found in Leick (2004), Hofmann-Wellenhof et al (1998) and Rizos (1997). Chapter 1 INTRODUCTION

Fig. 1.2. Double differencing (Roberts, 2005).

The other significant error in GPS observations is a systematic bias from medium propagation when the GPS signal passes through the atmosphere. Troposphere and ionosphere degrade the speed the GPS signal. Tropospheric and ionospheric delay will be discussed in chapter 5.

2«

l2j \ / 77

Measuied: x y z Delta: x y z

CoiTectioiis applied ; n \ Tii^: X y z I Tme: x y z Measured: x y z

Fig. 1.3. Real Time Kinematic GPS (Snay & Miller, 2001) Chapter I INTRODUCTION

Recently, the challenge of GPS applications in surveying is how to achieve centimetre accuracy in real time. RTK GPS requires differential positioning between two GPS receivers: A base and a rover. A base station must be set up over a known mark at the start and end of every day (see fig. 1.3). It must have a continuous power supply, clear skyview, good radio propagation and be secure in order that one or more rover users can work efficiently. RTK GPS uses carrier phase measurements that are transmitted from a reference station (base) to users with a rover receiver in real time. The rover combines the base data with its own GPS receiver data, initialises (resolves ambiguities) in a few seconds and produces cm-level positions in the field with real time updates. Sophisticated algorithms are applied for resolving the ambiguity while the rover is moving (on- the-fly).

Single base RTK GPS comprises many components in order to function reliably and produce correct results. Best practice guidelines give the GPS surveyor tools to check work and ensure that real time positions given in the field are true. This is particularly important for cadastral surveys which legally define land parcel boundaries. In recent times, national mapping agencies have set up permanent base stations so that roving users do not have the burden of base station management.

This has evolved in the development of Continuously Operating Reference Station (CORS) networks. Ultimately national mapping agencies hope to reduce the number of classical ground control points that they must maintain in order to support national mapping and land administration. The development of CORS networks combined with communications infrastructure allows real time applications, the most advanced of which is network RTK GPS. SWEPOS in Sweden and SAPOS in Germany are examples of network RTK infrastructure which are used for a range of applications including cadastral surveying (German State Survey, 2004; Hedling et al, 2001). CORS networks are established mainly in metropolitan regions as they require well established infrastructure such as Chapter 1 INTRODUCTION

power, security and reliable communications-often not found in rural areas. The business case for establishing a CORS infrastructure usually requires a suite of applications to secure government funding. This is another reason that CORS networks cover metropolitan areas-despite important scientific objectives which might be required in rural areas.

Deploying a full CORS network in Aceh after the disaster would be impossible to do due to the lack of supporting infrastructure; predominantly communications mechanisms. However the feasibility of a "re-packable" temporary CORS network is tested in this thesis. A temporary network could be established in a remote area and be used for land reconstruction, and when finished, the entire network could be moved to a new region leaving just the monuments which could be re-occupied at a later date if necessary. Communications for network RTK operations would be "over-the-air" presenting a significant logistical challenge. To avoid this extra complication, for this research project, static data was logged at nominated reference stations and some rover points and then this data was re- processed in a simulated network RTK mode. The Leica SpiderNet network RTK management software provides this facility.

Current literature discusses the establishment of CORS networks with network RTK capabilities which are used for a range of applications including cadastral surveying (Stone, 2000; Rizos et al, 2002; Willgalis et al, 2002; Gledhill, 2004; Busies, 2006; Harris, 2006). This infrastructure is suitable for developed countries with stable and reliable communications, power infrastructure and most importantly adequate and ongoing funding. The benefits for high productivity, cm-level positioning are profound (German State Survey, 2004). The literature (Stone, 2000; Cruddace et al 2002; Rizos, 2002; Chelik et al, 2006; Stone, 2006) presents basic requirements for establishing real-time (or active) networks such as monumentation standards, equipment and software standards, different algorithms used such as Virtual Reference Station (VRS), FKP, Master Auxiliary Concept (MAC) and even business models to maintain the infrastructure. Chapter 1 INTRODUCTION

However nowhere in the literature is there a proposal for providing such an infrastructure on a temporary basis over a smaller region and "leap-frogging" the expensive hardware (the "engine" of the network) to a neighbouring region leaving only fixed monuments with known coordinates.

This thesis will investigate a proof-of-concept temporary CORS network for developing countries for disaster management or even as a low-cost or high productivity means of cadastral surveying for land administration purposes.

1.2. Scope of the Research

The research investigates the feasibility of a temporary CORS network RTK approach for land reconstruction after the earthquake and tsunami in Indonesia. There were two kinds of research activities. Firstly a field campaign was conducted in Banda Aceh, Aceh Province, Sumatra, Indonesia. This fieldwork included design, survey planning and GPS data collection (reference stations and rover points). Communications options as required for network RTK operations were ignored due to the lack of infrastructure and limited time of the study. Secondly, this data was re-processed in a mode that simulated real-time network RTK GPS to compare Network RTK vs. static operations and single base RTK. This process involved reference station data processing using the AUSPOS online facility (AUSPOS, 2007) to obtain reference station coordinates and a network RTK simulation using the Leica SpiderNet software in a re-process mode. Due to data difficulties, a comparison data set from the Singapore Satellite Positioning Reference Network (SiReNT) in Singapore was accessed from the Singapore Land Authority (SLA) to carry out useful comparisons.

The research analysis investigated some distinct issues. First of all, a site reference analysis that involved satellite visibility based on a skyplot diagram, GDOP and the number of satellites was conducted. Network RTK data processing Chapter 1 INTRODUCTION

was compared with static GPS processing. In this step, there was an epoch by epoch analysis with respect to the static baseline, common satellite analysis between reference stations and then testing the network RTK RINEX result with the actual GPS data from master reference station. The third analysis was similar to the second but the objective of this analysis was to investigate the effect of the ionosphere by comparing single frequency LI only results with dual frequency processing.

This research, however, is a preliminary result for the possibility of using network RTK after a natural hazard but it also gave an option, alternative and challenge for Indonesian authorities related to relief and land reconstruction. It would depend on Indonesian authorities as decision makers to adopt this research. Further research in developing the communications such as using WiMAX and Wireless Broadband Access (WBA) that is available at the moment in Banda Aceh should be addressed.

1.3. Research Aims

The aim of this research is to investigate the possibility of implementing a temporary CORS network for land reconstruction in the absence of supporting infrastructure. It compares (in a post process mode) the accuracy and reliability of network RTK vs. single base RTK for cadastral surveying. It provides a possible alternative of using a temporary CORS network to cover tsunami affected areas for land reconstruction for more robust solutions. This research identifies many problems for setting up this infrastructure. Such a network, if established, could also support geodynamic monitoring at no extra cost. The technical focus of the research tackled the issue of ionospheric disturbances in equatorial regions and how this effects RTK GPS operations. Chapter 1 INTRODUCTION

1.4. Contribution to Research

Indonesia is situated between two large continents (Asia and Australia) and two large tectonic plates (Australasia and Eurasia). Indonesia is therefore susceptible to earthquake activity particularly along the west coast of Sumatera and south coast of Java which can trigger large scale tsunamis as experienced on December 26, 2004. Since early 2005, more than ten tsunami early warning systems had been installed along the west coast of Sumatra (Aglionby, 2005). As well as an early warning system, a geodetic infrastructure such as a CORS network needs to also be built in order to support geodynamic monitoring and for surveying and mapping operations in the aftermath of such disasters.

The issue of securing land property rights after a natural hazard is essential for re- establishing a functional society for the victims of the disaster and maintaining the land administration system. Cadastral relief and land reconstruction must be carried out quickly and correctly. Survey and mapping is an integral part of cadastral relief after a natural disaster. Many surveying methods had been implemented during the reconstruction works. One technique is RTK GPS for ground control point survey for the re-identification of land parcels. However RTK GPS suffers from limitations in coverage due to atmospheric and communication issues which produce potentially erroneous information. This research will conduct a trial to investigate the feasibility of using a temporary style network RTK approach and compare against single base RTK for usability, accuracy and reliability in a post processing mode. This is a preliminary study implementing a low cost CORS network for relief purposes.

1.5. Tentative Thesis Chapter

The thesis is divided into eight chapters. The first chapter presents an introduction that will cover the statement of the topic, scope of the research, research aim and Chapter ] INTRODUCTION

research contributions. The background and a brief history of the Boxing Day earthquake and tsunami, their effect in land administration and some projects related to land reconstruction will be addressed in chapter two. Surveying and mapping activities that have been conducted by Indonesian authorities also will be included in this chapter.

After reviewing the background, chapter three will continue in addressing the history of geodetic infrastructure in Indonesia and the use of GPS for cadastral surveying. Using GPS for land reconstruction is the main concern in this chapter. Chapter four will cover the history of CORS networks internationally and the considerations when establishing CORS infrastructure to support surveying, mapping and cadastral activities. Chapter five will explain the delay that is caused by ionospheric and tropospheric refraction as a limiting bias for GPS observations in equatorial regions. Issues such as linear combinations, Kp indexes and TEC mapping at the time of fieldwork as well as higher temperatures and evaporation rates will also be presented.

Chapter 6 deals with the field project carried out in Aceh and the establishment and problems encountered with the temporary CORS network for land reconstruction. The survey planning and fieldwork method will be discussed in this chapter. The processing of the data from the field project will be presented in chapter 7 (complete processing result is in Appendix). Due to problems with the collected data a comparison dataset from a well established network RTK infrastructure (SLA in Singapore) is processed using the same method. The final chapter draws a number of conclusions and recommendations for further research to both advance the idea of temporary CORS networks for land reconstruction but also proposes a wider CORS infrastructure for land administration and scientific purposes across Indonesia. Chapter 1 INTRODUCTION Chapter 2 BOXING DA Y EARTHQUAKE AND TSUNAMI IN A CEH

Chapter 2 BOXING DAY EARTHQUAKE AND TSUNAMI IN ACEH

On Boxing Day, Sunday 26 December 2004, a large earthquake with Mw 9.1 magnitude occurred on the west coast of northern Sumatra, Indonesia. The United States Geological Survey (USGS, 2004) stated that the epicenter of the earthquake was 30 km in depth and the coordinate location was 3°18'57.6" N and 95°51'14.4" E. The epicenter distance could be defined as (see fig 2.1):

1. 250 km (155 miles) South East of Banda Aceh, Sumatra, Indonesia. 2. 300 km (185 miles) West of Medan, Sumatra, Indonesia. 3. 1260 km (780 miles) South West of Bangkok, Thailand. 4. 1590 km (990 miles) North West of Jakarta, Java, Indonesia.

On the list of great earthquakes, it was the fourth largest earthquake in the world since 1900. The largest was a 9.5 magnitude quake located in Chile in 1960 followed by another 9.5 magnitude in 1964 in Prince William Sound, Alaska. The 3^^ largest in 1957 was 9.1 in magnitude on Andreanof Island, Alaska followed by the Boxing Day earthquake. The next largest was Kamchatka earthquake, with a magnitude of 9.0 in 1952 (Ibid, 2004).

The Sumatra earthquake, which began at midnight UTC time (7.58.53 am local time), became a trigger for large tsunami waves. They struck the coastal region twice. The first to strike was at 8.30 am and the second at 8.50 am. The wave traveled 4-5 km inland (Benny et al, 2006). The areas worst affected by the waves were the regions surrounding the epicenter: Indonesia (particularly in Aceh and Nias), Sri Lanka, India, Thailand and some countries on the east coast of Africa.

A few months before the earthquake and tsunamis struck, Geoscience Australia had predicted that the West Sumatran coast was a potential area for the generation Chapter 2 BOXING DA Y EARTHQUAKE AND TSUNAMI IN A CEH

of a large tsunami that would affect Sumatra, Java and Australia due to geodynamic plate motion (Geoscience Australia, 2004). The prediction was made based on geodynamic facts and historical conditions of the large number of earthquakes recorded that had hit Indonesia. Since 1833, some earthquakes followed by tsunamis have been recorded with massive destruction to Sumatra. In 1883, a large tsunami hit Sumatra and Java as a result of volcanic processes from Krakatoa Mountain. Then in 1977 and 1994, a large earthquake and tsunami occurred in the Sunda Arc and Sumbawa. The effect of these last two strikes reached Perth, Western Australia (Ibid, 2004).

The 2004 Great Sumatra Earthquake and Tsunami

26 DECEMBER 2004 EARTHQUAKE: 07.58 Local Time (WIB) TSUNAMI: 8.30 WIB REACHED COASTLINE AREA 8.50 WIB REACHED 4-5 KM INUND

INDIA

MmìÈS

Epicentres IVTALDIVES Mr Samara, %Ù masnitiiii Mmii ^ lUURsr tfygftHCtn^iif s beneamthé w » - i • Earth's surface 1000 t«LES tNnmuóci^àN Fig. 2.1. The epicenter and affected area (Benny et al, 2006)

An early press release after the Aceh event indicated that more than 200,000 people were killed during the earthquake and tsunami (Geoscience Australia, 2005). In addition, the Sydney Morning Herald (2005) stated that more than 100,000 people were missing and 500,000 people became refugees. The press Chapter 2 BOXING DA Y EARTHQUAKE AND TSUNAMI IN A CEH

release from the Indonesian Ministry of Health noted that approximately 166,000 people were dead, 6,000 people missing and 617,000 people had become homeless. Banda Aceh as the capital city of Nanggroe Aceh Darussalam Province suffered many losses in both infrastructure and lives particularly along the west coast where several villages and districts were completely lost. In addition, several towns Leupung, Lamno, Patek, Calang, Meulaboh and Simeuleu also suffered widespread destruction with no road access and consequently were completely isolated.

The earthquake also caused widespread deformation throughout Sumatera Island, particularly in North Sumatera. This deformation caused serious damage to geodetic and cadastral control points which underpin surveying and mapping systems. The deformation in the horizontal varied from 0.1-2.7 m and in the vertical between 0.04-0.32 m (Meilano et al, 2006). Independent research conducted by the Department of Physics, Syah Kuala University Banda Aceh and the Graduate School of Environmental Studies, Nagoya University detected that ground deformation continued until November. The value of deformation varied 25.5 ± 0.8 cm towards the south, and 26.6 ± 0.5 cm towards the west and 0.6 ± 1.8 cm uplift (Ohta et al, 2005).

93' 94' 95' 96' 9r 58" 99" 93' 94' 95' 96' 97 93' ?9' 100' Fig. 2.2. Ground displacement magnitude (Ibid, 2006) Chapter 2 BOXING DAY EARTHQUAKE AND TSUNAMI IN ACEH

2.1. Impact in Cadastral and Land Administration Systems

The reconstruction process after the disaster was more complex and required a multidisciplinary approach. As well as the thousands of victims, the tsunami destroyed municipal infrastructure, most dwellings and many basic social institutions such as land administration (Stanfield et al, 2005). A United Nations process was initiated to restore basic land administration which included recording, determining and disseminating information about ownership, value and land use. Land registration, cadastre, taxation and land use development and control also became a part of the land administration process.

Surveying and mapping activities, as a part of the cadastral process in spatial data recording, faced many obstacles to uncover some reference points due to the destruction. The earthquake and tsunami also affected the 3D location of both geodetic and cadastral control points. BPN (Badan Pertanahan Nasional), the Indonesian institution that has responsibility in land administration, identified 6 main impacts in the cadastral and land administration system after the earthquake and tsunami listed below (Benny et al, 2006):

1. Loss of physical evidence of land parcel boundaries. 2. Submergence of land parcels and land subsidence in particular areas. 3. Widespread land deformation. 4. Loss and damage of land documents. 5. Many land title holders became victims in the earthquake and tsunami. 6. Serious damage to BPN infrastructure and resources as the only institution responsible for land administration.

Furthermore, BPN (Ibid, 2006) also provided statistics that indicated the actual destruction in the Aceh land administration system as shown below: Chapter 2 BOXING DA Y EARTHQUAKE AND TSUNAMI IN ACEH

1. About 10% of land books were lost and the remaining 90% were in poor condition. Most were flooded by sea water and mud. 2. Almost 80% of land documents such as land certificates did not exist in the first place. 3. Cadastral map files, digital and analog, could not be used anymore. 4. About 300,000 land parcels were affected of which 170,000 were in urban areas and 130,000 were in rural areas. 5. There were a few land parcels that had not been registered yet also affected. 6. Conflicts in land rights due to potential inheritance numbered about 100,000 cases. 7. At least 5% of land parcels affected were mortgaged and were registered in the BPN office.

Fig. 2.3. The physical land books in poor condition after the tsunami (Winoto, 2005) Chapter 2 BOXING DAY EARTHQUAKE AND TSUNAMI IN ACEH

In addition, the earthquakes and tsunamis have changed the coast line along affected areas. This presented two main problems; some parcels were submerged by the sea and some unknown areas have risen from the sea. Therefore some people would have no parcels and some new land would have no owners. There is much to do to re-establish land parcels and rebuild a new land administration system due to the complex problems in Aceh.

Fig. 2.4. Manually identified land parcels due to a lack of cadastral maps (left picture). Loss of land parcel boundaries (right picture) (Benny et al, 2006).

After the earthquake and tsunami there were several new relationships between land parcels, land title holders, land certificates and supporting documents relating to the prevailing conditions (see table 2.1). There were few land parcels and land owners with complete documents. This problem often caused conflict for potential inheritance within or external to the families because many land title holders had died leaving widows or children exposed to land fraud. Chapter 2 BOXING DA Y EARTHQUAKE AND TSUNAMI IN A CEH

No, Land Parcel Owner Land certificate Official Document 1. Exist Exist Exist Exist Exist Exist Exist .\o Exist Exist No Exist Exist Exist No \o Exist No Exist Exist Exist No Exist No Exist No No Exist Exist No No So No Exist Exist Exist No Exist Exist So No Exist No Exist No Exist No So No No Exist i:xist No No Exist No No No No Exist No No No No

Table 2.1. The relationship between land parcels, land title holder, land certificate and supporting documents after the earthquake and tsunami (Ibid, 2006).

2.2. RALAS (Reconstruction of Aceh Land Administration System) Project

The reconstruction process after the destruction was always complex but the imperative was for relief for basic social institutions such as land administration to be executed quickly (Stanfield et al, 2005). In addition, Stanfield et al (2005) added land registration, cadastre, taxation and land use development and control as a part of land administration. The Government of the Republic of Indonesia realized that there must be quick and accurate action for securing land administration, because for most Indonesian citizens, land is the most important commodity.

The Government of the Republic of Indonesia in cooperation with the Multi- Donors Trust Fund for Aceh and North Sumatra (MDTFANS) and the Worid Bank have signed a Memorandum of Understanding (MoU) for Reconstruction of the Aceh Land Administration System (RALAS) project valued at USD $28.5 Million (MDTFANS, 2005). The MoU stated that the RALAS project was fully Chapter 2 BOXING DAY EARTHQUAKE AND TSUNAMI IN ACEH

supported for after disaster recovery, land rights protection, rehabilitation of the land administration system and the post-disaster reconstruction process in Aceh province until 2009.

As a representative of government for running this project, the Rehabilitation and Reconstruction Board (BRR) was founded straight after the MoU. The mission of ERR was providing resettlement for homeless people, rebuilding physical infrastructure as well as communications services, providing water and waste management. Spatial data management systems also became one of the BRR's main concerns. BRR has a responsibility for managing all spatial data and made it easy to share the data with all Non Government Organizations (NGO) and other International Organizations (Badan Rekonstruksi dan Rehabilitasi, 2005).

The project was started in July 2005 and focused on mapping activities for titling more than 225,000 land parcels (AIPRD, 2005). BPN as an Indonesian government agency in land administration is closely involved in running this project. The objectives were mainly in securing land property rights particularly for orphans and inheritors, re-establishing land administration systems and computerizing land databases and back up (MDTFANS, 2005). In addition, BPN also had special responsibility in surveying and mapping every land parcel and collecting this land parcel data. Community driven adjudication or community based mapping was conducted for completing the data about land ownership rights, land boundaries and inheritance agreement with local communities.

Representative spatial data infrastructure became a key success in this work. BRR, Indonesian Surveying and Mapping Agency (Bakosurtanal), BPN and the other international agencies collaborated to create good spatial data management. Bakosurtanal mainly provided a geodetic control network for mapping purposes and some geodynamic studies. BPN provided cadastral data and collected land information. BRR as a coordinator for all spatial data, created a spatial database and provided the access for all spatial data users. Chapter 2 BOXING DA Y EARTHQUAKE AND TSUNAMI IN A CEH

2.3. Surveying and Mapping

The critical process during the re-establishment of spatial planning of more than 300,000 parcels post disaster was updating maps and rebuilding a new mapping system as a blueprint for spatial development in the future (AIPRD, 2005). The existing map in Aceh was an old mid-1970's topographic map with small scale (1:50,000) with no specific changes or revisions of this map since it was released (Ibid, 2005). After the earthquakes and tsunamis, Aceh, particularly the worst tsunami affected areas, were mapped for different purposes for the relief project. The International Federation of Surveyors (FIG) (2006) stated that there were several items in which survey and mapping were closely related within the reconstruction process after natural disasters.

1. Combining and using different sources of spatial data such as aerial photography, satellite imagery and radar or multispectral images. 2. Computer based information systems could be designed as Geographic Information Systems that are helpful for spatial analysis, spatial decision making, hazard assessment and monitoring for early warning systems. 3. Accurate land use planning and land management systems for reducing natural disaster damage and environmental impact. 4. Satellite positioning technology for land parcel and cadastral infrastructure reconstruction.

Benny et al (2006) stated that the main activity for surveying and mapping as a part of the RALAS project was divided into two tasks; surveying and mapping with priority for securing land rights and for supporting the RALAS project. For securing land rights, there were three priorities in reestablishing land parcels. The first priority was capturing spatial data of approximately 100,000 land parcels for settlement, re-settlement and providing places for public facilities such as the offices, schools and hospitals. The second priority was approximately 200,000 Chapter 2 BOXING DAY EARTHQUAKE AND TSUNAMI IN ACEH

land parcels affected by the tsunami to be surveyed. The last priority was surveying adjacent affected areas comprising about 300,000 land parcels.

In order to support the RALAS project, a base map needed to be provided accurately. A large area survey and mapping project using satellite imagery and aerial photography had been taken by many agencies and BRR as well. In addition GPS and terrestrial survey had been completed for an engineering and infrastructure recovery project. The combination of these mapping projects will be a digital map, cadastral map record and index map that would support the strengthening of a new blue print of land administration and spatial planning.

Previously, the availability of a map in Aceh Province was a small scale topographic map from Bakosurtanal. Currently, the mapping status in Aceh is quite confusing. Many NGOs and some Indonesian government agencies conducted several surveying and mapping projects for different purposes. This situation was inefficient as there will be many mapping products, some overlap areas of mapping and some affected areas could be missed. Fig 2.5 shows the overlapping mapping area. The green area was the satellite imagery mapping project from Bakosurtanal funded by the Norwegian government which in some areas overlaps with red zone. The red zone was a mapping project that had been conducted by AusAid and the Indonesian government. Chapter 2 BOXING DA Y EARTHQUAKE AND TSUNAMI IN CEH

Fig. 2.5. Location of satellite imagery mapping (AIPRD, 2005)

The solutions were concerned with mapping assessment based on map usability and spatial development purposes. AusAid developed some items for basic mapping assessment listed below:

1. Government and NGOs needed usable comprehensive maps between departments and NGOs. 2. The kind of data needed was specified. 3. Assessment of main mapping activities based on its primary use. 4. General mapping scale and map data.

2.4. Rebuilding the Cadastral System after the Shock

The RALAS project has been launched for reconstruction and to relieve land administration problems after the earthquake and tsunami. The main aspect in this project was re-settling people and re-developing the system for regional areas. In terms of long term economic development, re-building the cadastral system as a main legal guarantee for land title was the major concern in this project. The main Chapter 2 BOXING DA Y EARTHQUAKE AND TSUNAMI IN A CEH

focus in cadastral reconstruction was about repairing the land database, land records, land administration systems, infrastructure and cadastral mapping system.

The cadastral re-development involved many human resources from outside Aceh because many BPN employees became victims as well. In addition, the old land administration system was still in paper based form for data storage (land book). The new system would be designed in digital form and a multi data base infrastructure. This database recovery became crucial since the paper based records (land books particularly) were damaged with no back up. Cleaning and scanning land books in large volumes became a priority for migrating and saving the land database. It is hoped that this recorded data would be the core base for the new Land Management Information System.

Cadastral system recovery also sought to provide areas for refugee re-settlement. Surveying and mapping for parcel reconstruction and parcel re-settlement must also consider special circumstances with potential land conflicts. The survey was combined with social aspects, economic and legal complications. GPS and terrestrial surveying have been combined in order to create a geo reference system. In addition, some satellite imagery and aerial photogrammetric mapping also have been used to aid land identification. The rectified ortho photo is the main objective for future spatial planning.

On the other hand, the stability of Aceh basin will continue to be a problem. Geodynamic activity after the earthquake will influence the point positioning on the Earth. For an active area such as Aceh, the cadastral reference point must reflect this movement. An active reference station must be connected to a global reference system and perhaps can update their position in real time.

Recently, active reference stations have been deployed in some countries such as Germany with the Satelliten Positionierungdienst (SAPOS) GPS network and in Sweden with SWEPOS for maintaining cadastral surveys (German State Survey, Chapter 2 BOXING DA Y EARTHQUAKE AND TSUNAMI IN ACEH

2004; Hedling et al, 2001). Several GPS receivers connected into a communication network could possibly replace many but not all classical control points. The demand of database connectivity between spatial data captured and Land Information Systems is inevitable for handling a modern cadastre using a more trustworthy method (Eren & Uzel, 2006). Furthermore, the active reference point will comprise the following functions:

1. Providing more accurate positioning data with low cost, much faster and at a high level of confidence. 2. Overcoming classical cadastral problems in coordinate systems and migrating the old system into a new one. 3. Contributing to high accuracy real time geodynamic monitoring and giving a perspective of magnitude and direction of continuous land deformation.

Hopefully, the new system that will be built includes new active reference system particularly Network RTK GPS. This system will give a new perspective to cadastral activities and database maintenance systems as well as providing valuable geodynamic monitoring information. The next chapter will give the history of using GPS for cadastral surveying in Indonesia and related issues. Chapter 3 GPS FOR CADASTRAL SURVEYING IN INDONESIA

Chapter 3 GPS FOR CADASTRAL SURVEYING IN INDONESIA

3.1. The Cadastral System in Indonesia, an Overview

In 1995, the International Federation of Surveyors (FIG) provided an operational definition of the cadastre as "a parcel-based and up-to-date land information system containing a record of interest in the lands (e.g. rights, restrictions and responsibilities). It usually includes a geometric description of land parcels, links to other records describing the nature of interests, and often the value of the parcel and its improvements" (FIG, 2005).

Western communities since the pre-industrial period acknowledge that land has been a symbol of prestige and wealth. In that era, the cadastre became a part of land administration and was used as a basis for taxation. The value of land increased dramatically during the post war reconstruction period and served as an instrument for planning. More recently the rise of sustainable development issues and response to land degradation has meant the cadastre plays an important role in land management as well (Williamson, 1999).

The development of the cadastral system in Indonesia was established by the Dutch colonial government for more than 350 years. (Walijatun & Grant, 1996). In addition, the colonial regulations on 18 August 1620 were used for controlling the land and distributing it to their employee inhabitants who had resettled from the Netherland (Cadastral Template, 2003).

After the Indonesian Independence Day on 17 August 1945, the Dutch system was still in use as the main cadastral system. It required approximately 15 years to create and establish a new cadastral system. Indonesian National Agrarian Law was established in 1960 and began a new era for the Indonesian cadastral system Chapter 3 GPS FOR CADASTRAL SURVEYING IN INDONESIA

to replace the Dutch colonial system. This new regulation accommodated traditional cadastral concepts that are different in every region. However, there were still many influences from the old system such as the measurement method and the method of cadastral recording (Walijatun & Grant, 1996). Then, in 1961, the Government Regulation No. 10/1961 about the Indonesian land administration system was released to support the National Agrarian Law 1960. The newly established system was a negative system within registration of titling and fiscal cadastre (Cadastral Template, 2003). The negative system means that the certificate of land titles are issued by the Land Office (there was a BPN representative in every city) and they are valid as legal and strong evidence.

This new regulation was hoped to accommodate the migration from the Dutch system (whilst maintain the traditional concepts) into the Indonesian national land administration system. Many problems have arisen since the decision to migrate from the Dutch colonial scheme into the national system. The development of the cadastre in Indonesia must accommodate a population of more than 200 million people widely spread across about 80 million land parcels over 17,000 islands- some very remote (Walijatun & Grant, 1996). This is an ongoing task with some Dutch colonial systems developed more than 350 years ago only recently upgraded. Indonesia is a unified state that maintains centralized cadastral parcel based records in a land administration office in each city, most of which are still manual. 38 land offices are moving towards computerization. However, they are still manual in most offices (Cadastral Template, 2003). Chapter 3 GPS FOR CADASTRAL SURVEYING IN INDONESIA

Fig. 3.1. Indonesian archipelago, courtesy Google Earth.

According to Harsono (1983), the legal aspects of land registration conducted by the Indonesian Government is clearly stated in the Indonesian Agrarian Law 1960. Cadastral surveying is one of the main activities in land registration. Cadastral surveying refers to an activity related to land measurement (parcel based) and maintenance of the land administration (ownership, area, title, land value and location). The Indonesian Government adopts two cadastral systems. The first system is the Fiscal Cadastre (FC) which is designed to collect land and building taxes and is conducted by the Directorate of Land and Building Tax Office (PBB) of the Ministry of Finance. The other is Recht Cadastre (RC). It deals with legal aspects of land title. The BPN is the official government agency responsible to the RC. Cadastral surveys can be performed by private surveyors or BPN employees.

Conceptually, these institutions have different approaches to cadastral mapping. The PBB focuses on the land itself and the properties on the land and Chapter 3 GPS FOR CADASTRAL SURVEYING IN INDONESIA

improvements for taxation purposes. BPN is concerned with the physical cadastre, that is the location and mapping of parcels of land and their associated accuracy. To complicate things further, different systems of grid coordinates were adopted for the two different cadastres. The Recht cadastre uses a derivative of the UTM projection called the TM3 coordinate projection while the Fiscal cadastre is described using the UTM projection system. However, both systems require the same datum ID95. More explanation about the Indonesian datum will be addressed in section 3.3. This differentiation means that additional effort is needed to relate products from both institutions. Achmad (2004) argued that BPN products support the Land Information System and the FEB products support a Geographic Information System, as shown in the following fig 3.2.

Un^

L^Use Spatjat Plarmtng • LaidOwner^p Strategic Pi mning Operational Planning • Land Use

ESRIArcSDQ Data Sources: SMALLWOf^ AutoCAD • JANTOP Msps, RBI. Satellte BASE MAPS • BAPPEDA • Ortophoto, IKONOS, PT, PP.10, ORACLE PRONA, PBB MultiBase dB£Be3 MS Access

Fig. 3.2. Current status of cadastral and spatial databases in Indonesia (Ibid, 2004)

There were approximately 25 million land titles on the record in the 44 years since the commencement of the 1960's Indonesian National Agrarian Law. In addition, only a quarter of registered parcels have been mapped to the national standard of cadastral mapping and subsequently stored in the database (Achmad, 2004). The remaining parcels are still problematic in terms of their location. Uncertain parcel Chapter 3 GPS FOR CADASTRAL SURVEYING IN INDONESIA

location presents difficult challenges for land administration. This problem is widespread in all Indonesian regions.

From a geodetic perspective, this problem is mainly due to inconsistencies on the use of coordinate systems. In some regions, local coordinate systems were employed in cadastral surveys (Ibid, 2004). Therefore, connection to existing cadastral networks is often neglected or minimal. The misconception between geodesy and cadastre has been tolerable because of the nature of the Indonesian archipelago. Consequently, it has been a difficult and expensive task to build cadastral control networks across the nation. The history of relating the geodetic and cadastral network development in Indonesia will be addressed in section 3.2.

Some old cadastral control points inherited from the colonial system are still used. Nonetheless, problems occurred since the control points were established in different mapping systems with current Indonesian cadastral standards. The recent Indonesian datum is the Indonesian Datum 1995 (ID95) which has the same parameters (semi major axis = 6,378,137 m and inverse flattening 1/f = 298.257223563 m) with the GPS datum WGS84. On the other hand, the old colonial mapping system used the Bessel system as the main ellipsoidal datum which was commonly used in Europe. In recent years therefore the main duties of the cadastral survey include extending cadastral control networks for a unified mapping system and updating the database by transforming local coordinated land parcels into a national cadastral system (i.e. from the Bessel datum to the ID95).

In 1997, the Indonesian Government released the new regulation for supporting land administration to replace the old one (Government Regulation No. 10/1961). The regulation was Government Regulation No. 24/1997 regarding Land Administration in Indonesia. This regulation could be considered as a "break through" in land administration systems in Indonesia, because it allows the use of the computer as a data record management tool as well as allowing GPS for cadastral surveying. However, this regulation did not clearly state how GPS can Chapter J GPS FOR CADASTRAL SURVEYING IN INDONESIA

be used as a method in cadastral surveying. It only stated that the regulation accommodated the using of GPS for speeding up the surveying process. In addition, in 1997, there was a project called the Land Administration Project Phase I that tried to re-establish the unification of colonial and traditional cadastral systems into the national system.

In addition, the sub regulation, PMNA No. 3/1997, clearly stated that TM3 is the national coordinate system for cadastral surveying in Indonesia. Therefore, the impact of this regulation that all parcels that are registered must be coordinated in the TM3 system. It is now over 40 years since the commencement of the first Indonesian national cadastral coordinate system. Two main problems remain. First, the system needs to be transformed from the Dutch colonial system into the Indonesian national system as well as its coordinate system and datum. The second problem deals with transforming the disintegrated coordinate system (local) from 1960-1997 into the TM3 coordinate system.

Since the mid 1990s, GPS has been used for survey and mapping activities in Indonesia, particularly geodetic applications which require high accuracy. GPS is used in cadastral surveying to provide high order control point surveys. The use of GPS measurements allows better results with regard to accuracy, and with fast ambiguity resolution techniques, cadastral surveys can be conducted more quickly. The details about the geodetic framework, GPS and their relation will be addressed in section 3.3.

3.2. GPS in Cadastral Surveying

Since 1997, the Indonesian government "allowed" the utilization of GPS to accelerate cadastral surveying in land registration (Government Regulation No. 24, 1997). However, it was not a specific guideline or regulations for best practice, accuracy or to specifically declare GPS to be acceptable in cadastral surveying. In fact, GPS has been used in Indonesia for surveying the three highest Chapter 3 GPS FOR CADASTRAL SURVEYING IN INDONESIA

orders of cadastral control networks (2"^ and orders), despite GPS implementation not being regulated. It started to be used in Land Administration Project Phase I (1997-2000) which was 10,402 order points surveyed using GPS across Indonesia (Nasoetion, 2002). In addition, for some cadastral surveyors, the technology is unfamiliar. Cadastral surveying, traditionally, relies on angle and distance; while GPS gives a pair of coordinates as a result (Roberts, 2006).

The other use of GPS is for registering farmland. Farmland covers large areas and traditional surveying techniques, requiring line-of-sight, are slow and labour intensive compared to GPS. Also farmland in remote regions is unlikely to suffer land conflicts resulting from boundary disputes.

In order to adopt FIG's vision of a "Legal Digital Cadastre 2014" (Kaufmann, 2002), Indonesia needs to upgrade their analog cadastre into a digital cadastral system. This upgrading includes preparation to create new cadastral regulations and cadastral survey instruments (Jarroush et al, 2005). Modem surveying instruments, such as GPS, have been used by cadastral surveyors due to their suitability for certain conditions and circumstances however the replacement of traditional instruments such as Total Station is unnecessary (Roberts, 2005).

Verseema (2004) presented a comparison between RTK GPS and Total Stations. In his project, RTK GPS was compared to conventional Total Station traversing for boundary marks surveying on the basis of accuracy, efficiency and cost as well as their practicality. The results indicated that the discrepancy on the coordinate vector in easting and northing was below 6 cm with average divergence less than 3.5 cm at a standard deviation of 1.4 cm. Furthermore, on cost and efficiency, Total Stations required 9.5 hours to complete a particular case study survey with connection to State Survey Marks. In comparison, RTK GPS only needed 4 hours for this task. Although GPS could compete with traditional measurements, there was a concern in using GPS for cadastral surveying due to some regulations and Chapter 3 GPS FOR CADASTRAL SURVEYING IN INDONESIA

legislation in cadastral surveying (Kardiasmenos, 2005). Ultimately consideration of a legal coordinated cadastre supported by GPS techniques threatens to contravene the principle of "monuments over measurements" and land parcels could simply be re-established using coordinates (Blanchfield and Elfick, 2006).

Nevertheless, there is a disagreement among surveying professionals on the use of GPS in cadastral surveying. This is due to a limited understanding on geodetic concepts and best practices on the use of GPS to fulfill cadastral regulations (Ibid, 2005). With regard to survey regulations, Hansen (1998) stated that there are two basic principles that need to be fulfilled for deployment of RTK GPS to be accepted and incorporated on cadastral surveys. Requirements of "High Neighboring Accuracy" and "High Positional Accuracy" relative to datum reference are required to maintain the relationship to existing geodetic networks.

Indonesia is quite slow in accommodating GPS for cadastral surveying. Although it is currently being used for cadastral work, there is still no clear regulation for the legal use of GPS. The Indonesian authorities realized that they needed to speed up the cadastral process for legal guarantee purposes. Despite no specific regulations, GPS is still used as a cadastral tool.

3.3. Geodetic Infrastructure

Historically, the development of geodetic infrastructure in Indonesia was predominantly for surveying and mapping the colonial interests of the Dutch. The Bessel system was the main ellipsoid reference as well as geodetic control points that were established across the islands. The development of geodetic control survey using modern surveying technology was started in the early 1970s for providing a national spatial data infrastructure (Matindas et al, 2003). This development was mainly using space based positioning from the satellite transit Doppler (NWL-9) system. In addition, the Doppler satellite system was deployed for replacing the Bessel datum with an Indonesian national datum. The datum was Chapter 3 GPS FOR CADASTRAL SURVEYING IN INDONESIA

called Indonesian Datum 1974 (ID74). By the end of 1990, there were 1258 Doppler points widespread around the islands that would be used as integration for local coordinate systems into the national geodetic coordinate system based on ID74 (Ibid, 2003).

In the development of geodetic infrastructure in Indonesia, Doppler points had been used for boundary fixing between Indonesia and the other countries such as Papua New Guinea in 1983 (Ibid, 2003). But since early 1990, the preference for using Doppler satellites changed with the development of GPS since GPS has been used for some geodynamic projects (GEODYSSEA and GPS-GPS). GPS has led to the updating of the Indonesian datum from ID74 into ID95 with particular datum transformation (Bursa Wolf and Affinity model). As mentioned in section 3.1, the ID95 has identical ellipsoid parameters to WGS84. The first established geodetic network using GPS was the zero order points measured in 1992 for precise national horizontal network unification. The points were staged island by island with the inter station distance more than 100 km. The coordinate result was adjusted into the ITRF91 system and then was transformed to ID95 (Ibid, 2003). Then, the 500 first order points for network density was built widespread across the nation with the inter distance about 150-300 km. These two orders were derived into the Indonesian GPS network which was to become a "backbone" for ID95 (Ibid, 2003).

For more than a decade, the GPS application has been used for geodetic and surveying applicafions. A GPS permanent tracking station was successfully built in Medan, Cibinong, Pare - Pare, Kupang and Biak as a participafion of Asia Pacific GPS tracking station and GIS infrastructure project in the Asia Pacific region. The other deployment of GPS was for boundary determination between country borders with surrounding countries and geodynamic network monitoring in the Sumatran plate and Papua. In addition, some MoUs related to GPS projects for land subduction and volcano deformation monitoring in Java were signed Chapter 3 GPS FOR CADASTRAL SURVEYING IN INDONESIA

between the Indonesian government and the University of New South Wales (Ibid, 2003).

45'E 90'E 135'E 180' ISS'W 90'W 45'W 0'

60'N 60*N

%LK ^ 60'S VIJBI

45'E 90*E 135*E 180* 135'W 90'W 45'W 0*

Fig. 3.3. Indonesian GPS tracking stations between the other stations in the world (Manning et al, 1998)

Bakosurtanal is the Indonesian government institution that is responsible for all geodetic surveying and mapping matters including determining the Earth dimensions (gravity, tide and geo-hazards). In surveying and mapping, Bakosurtanal is responsible for developing zero and first order networks across the nation. In addition, for network densification, BPN continues densifying this network into and order. Although the Bakosurtanal points and the BPN points use a similar datum (ID95), both use a different map projection to produce grid coordinates. UTM is used by Bakosurtanal and BPN uses TM3. BPN points are also called cadastral control points. The order classification is based on the distance between every point. The distance of the order is classified as listed below:

1. Zero order: more than 100 km. Chapter 3 GPS FOR CADASTRAL SURVEYING IN INDONESIA

2. First order: 50-100 km. 3. Second order: 10-15 km. 4. Third order: 1-3 km. 5. Fourth order: 150 m.

The cadastral surveying process requires the parcels to be referenced from one particular order (note: zero and order have different map projection with 2"^, 3^^ and order). Therefore, it is hoped that all parcels that are already registered are also geo-referenced. In fact, it is difficult to fulfill this requirement. Sometimes, the distance between land parcels and the nearest cadastral control point is too large. Therefore, it will be very difficult and costly to geo-reference the land parcel. In addition, sometimes the availability of cadastral control point is not widespread across the area, particularly in remote areas. This leads into the problem for cadastral surveys with regard to geo-referencing within a geodetic framework.

In the early era of GPS surveying, centimeter accuracy could only be achieved using static, post processing techniques with observations of approximately one hour depending upon baseline length and other conditions. Recent developments have demonstrated that RTK GPS could obtain similar accuracy with significantly shorter observation periods (Busies, 2006). GPS, and specifically RTK GPS, as a surveying instrument has matured with regard to usability and reliability (Roberts, 2005). Consequently survey productivity using GPS techniques can be increased significantly. Some tests have been done for comparing RTK GPS and cadastral surveying instruments such as total station as mentioned in section 3.2. The test concluded that RTK GPS is reliable for use in rural area cadastral surveying in terms of accuracy, efficiency and practicality (Verseema, 2004).

GPS can be used to geo-reference parcels. On the other hand, some cadastral surveyors and institutions are still very reluctant on the use of GPS. Common arguments refer to the high cost of GPS instruments, misunderstanding of Chapter 3 GPS FOR CADASTRAL SURVEYING IN INDONESIA

geodetic basic concepts, less information about GPS surveying capabilities, best technique to use, and regulation in cadastral surveys when using GPS (Roberts, 2005). This issue is quite relevant in cadastral surveying due to some obstacles related to GPS performance in particular areas. GPS only works well in the clear sky view area, with minimum multipath, a good satellite constellation and no interference. But, how is GPS working in the metropolitan environment with high rise buildings, minimum clear sky view and full interference from electromagnetic waves and pulse (for communications)? Cadastral surveying activities are everywhere; urban, suburban and metropolitan areas. However, the cadastral surveying result without geo-referencing is not appropriate for strengthening the spatial database. GPS could perform as a geo-reference tool if the survey location is far away from a cadastral benchmark.

The adoption of the futuristic FIG vision of a digital cadastral database (Digital Cadastre 2014), gaining real time results for cadastral surveys is desired. It is obvious that cadastral benchmarks must therefore be based on a permanent GPS control network to obtain high precision for cadastral land parcels on a national scale (Jarroush et al, 2(X)5). The geodetic infrastructure has been used as cadastral infrastructure as well. In many cases, land authorities provide such assistance in the establishment of these infrastructures such as illustrated by the Department of Lands of New South Wales, Australia in collaboration with the University of New South Wales (UNSW) and the establishment of a CORS (Continuously Operating Reference Stations) network called SydNet. The history about CORS networks and their development will be addressed in chapter 4. Chapter 3 GPS FOR CADASTRAL SURVEYING IN INDONESIA

Fig. 3.4. SydNet permanent stations across Sydney (Roberts, 2006).

A further question is what the actual function of this geodetic infrastructure will be for cadastral activities. The large number of cadastral benchmarks needs to be maintained and checked regularly for keeping them secure and up-to-date. Sometimes, manual records are still used. In Indonesia, which has a density of cadastral benchmarks every 150 m (see section 3.3), still maintains a manual record of cadastral points. This is an expensive and ineffective situation because most of the budget could only be spent for point maintenance every year. On the other hand, the GPS permanent infrastructure can deal with coordinate system problems and requires comparatively minimal maintenance. Therefore, the high density of cadastral benchmarks could be replaced by the GPS permanent control network and a sparser array of ground marks. Chapter 3 GPS FOR CADASTRAL SURVEYING IN INDONESIA

Fig. 3.5. GPS permanent stations (Leica, 2007) & (Burbidge, 2007)

This infrastructure should consist of GPS receivers as a permanent network that has global datum reference, such as WGS84 which has the same dimension with ID95.

3.4. Using GPS for Land Reconstruction in Aceh

GPS applications in support of earthquake and tsunami relief is inevitable for land reconstruction and cadastral recovery. GPS was used extensively in response to the Aceh earthquake and tsunami. The Indonesian Government Regulation 24/1997 stated that GPS can be used for cadastral surveying to support spatial data collection. It is also interesting to see that GPS serves on re-establishing and re-coordinating approximately 300,000 land parcels in the Tsunami affected area (Benny et al, 2006). However, there is no specific regulation and guidance that clearly states the accuracy, requirement, coordinate conversion that has to be fulfilled through GPS surveying.

The use of RTK GPS gives many advantages in cadastral surveying especially when seeking survey marks (Verseema, 2004). High productivity surveying at centimeter-level accuracy could be achieved but this relies on successful Chapter 3 GPS FOR CADASTRAL SURVEYING IN INDONESIA

initialization (i.e. ambiguity resolution) (Roberts, 2005). In the Aceh disaster, more than 10,000 land parcels were destroyed during the earthquakes and tsunamis (Benny et al, 2006). Single based RTK implemented for re-survey and re-coordinating land parcel boundaries has severe limitations due to the distance constraints between the reference and rover receiver (usually less than 10 km) to ensure quick ambiguity resolution (Rizos et al, 2003). In addition, undulating topography is present in the area, therefore limiting the utilization of single based RTK due to obstructed communications.

GPS itself, or in combination with the other terrestrial surveying methods, has been used for re-locating and re-coordinating land boundaries. The initial role for land reconstruction using GPS was for seeking cadastral boundary marks which have WGS84 coordinates. It was then extended for coordinate determination and establishment after completing agreements and common boundary definitions as shown below: Chapter 3 GPS FOR CADASTRAL SURVEYING IN INDONESIA

Finding the location • Utilizing GPS technology if the previous WGS84 of missing boundary coordinates of boundary are known. points in the field • Utilizing terrestrial surveying principles if the previous coordinates are known in local coordinate system. • Utilizing natural or man-made objects around the parcels if they are still exist. • Utilizing the help of aerial photos or satellite imagery of the area. • Utilizing information given by the owner (if still alive), inheritors, neighbours, family members, and/or community around the affected parcels.

Adjudication Consultation and agreement with the owner (if still Establishing agreement alive), inheritors, neighbours, family members, and/or on the recovered location community around the affected parcels. of boundary points. I • GPS surveying. C oordi nate determi nation • Terrestrial surveying. of the adjudicated boundary jx>ints • Combination of GPS and terrestrial surveying.

Fig. 3.6. GPS included in the parcel boundary reconstruction process (adopted from Benny et al, 2006)

As shown on fig 3.6, there are two steps in the use of GPS for land reconstruction in Aceh. The first step is using GPS to search some cadastral control points and missing parcel identifiers. At least a few cadastral control points were identifiable after the tsunami, nonetheless, their positions needed to be re-surveyed due to the huge ground displacement: between 0.1-2.7 m (Meilano et al, 2006). GPS is also employed for creating rectified satellite imagery and orthophotographs. Those data are combined together for land parcel identification. The second step relates to the utilization of GPS techniques for coordinating all adjudicated boundary points in the new cadastral system.

GPS is likely to become a reliable technique providing high productivity and accuracy. In addition, GPS is not only useful for geodetic surveying or in Chapter 3 GPS FOR CADASTRAL SURVEYING IN INDONESIA

determining cadastral control points but also can be used for land parcel surveys. RTK GPS has performed well with high productivity for re-survey of parcel boundaries in Aceh. About 120 parcels could be surveyed in a day compared to about 110 land parcels in 4 days using conventional Total Station techniques (Ibid, 2006).

Example of parcel boundary Example of parcel boundary determination in Aceh with GPS. determination in Aceh with Total Station

120 parcels in 1 day 110 parcels in 4 days

Fig. 3.7. Parcel boundaries survey with GPS and Total Station (Benny et al, 2006)

The destruction of infrastructure has presented an opportunity to re-arrange land parcel boundaries and set up a new mapping system and spatial database in Aceh. Convergence between the geodetic framework and the cadastre could be created by unification of these systems using GPS techniques. In fact, before the disaster, Aceh had the similar problem with other provinces in Indonesia in dealing with the migration to the national cadastral system. Numerous land parcels had not been mapped properly and had not been geo-referenced.

Overall, land reconstruction in Aceh does not only need surveying and niapping from a cadastral point of view. More specifically, the special characteristic of this natural hazard affected area needs to be known as an informal approach. The primary and most important aspect is the social approach and family discussion to determine ownership. This approach has produced many successful results in providing the correct information for land parcel definition before the GPS survey Chapter 3 GPS FOR CADASTRAL SURVEYING IN INDONESIA

begins. Once this has been achieved, high accuracy, high productivity and system unification would be assisted using GPS survey techniques. However this stage requires more than just providing or re-establishing control points that have previously existed. This process also requires an over arching geodetic infrastructure to manage all spatial coordinate data input into the future.

This proposal is a Utopian idea, however such a proposal for a new effective system for land reconstruction is definitely required and achievable. The system would be expensive to establish in the first instance, however it would contribute to efficiencies in the future in comparison to continuing to build classical control points in an ad hoc fashion and the associated maintenance costs required thereafter.

The following chapter will cover the early establishment of CORS networks in Indonesia and some international perspectives. Further discussion will reinforce the requirement for establishing the network. Chapter 4 CONTINUOUSLY OPERATING REFERENCE STATION (CORS) NETWORK

Chapter 4 CONTINUOUSLY OPERATING REFERENCE STATION (CORS) NETWORKS

Many applications in surveying, mapping and its related fields require high accuracy. When using GPS, this requires the use of relative positioning techniques between two or more GPS receivers whereby one acts as a reference station and one (or more) act as roving station(s) (Stone, 2000). Recently, many organizations have been building fixed reference facilities that collect and record GPS data at known points to support these activities. The facilities are widely known as GPS Continuously Operating Reference Stations (CORS) which form networks over regional areas. An example of this has been established by the United States National Geodetic Survey (Ibid, 2000). These reference stations had been further developed to provide real time data within the network as data services for high productivity GPS users who therefore only require one GPS receiver. The user collects data from their own GPS receiver and simultaneously receives data from a nominated reference station via a communications link (radio or another data transfer format) (Ibid, 2000). This data is then combined and processed in the field automatically inside the roving GPS unit to produce real time positioning in the field at centimeter level accuracy.

4.1. History of CORS Networks

The advent of GPS as a highly accurate and relatively inexpensive means of measuring long distances made it a suitable new technology for high precision geodynamic and geodetic studies. The application of GPS for geodesy started in mid 1980s which the focus of study in crustal deformation and earthquake research in California (Bock et al, 2002). Since 1909 after the massive San Francisco earthquake, California has been a large "incubator" for high precision geodetic research (Ibid, 2002). Initially GPS research was conducted in campaigns Chapter 4 CONTINUOUSLY OPERATING REFERENCE STATION (CORS) NETWORK to measure and then re-measure (usually in 2 year epochs) stable marks. Two campaigns gave an indication of the magnitude of movement and three campaigns gave a better estimation of the velocity. However researchers wanted to catch an earthquake as it happened. The only way to do this was with CORS stations. Continuous monitoring stations were established for measuring (and monitoring) plate tectonic movements in regional areas with known tectonic activity. The first regional CORS network was established in Southern California around the San Andreas Fault in 1990 (the permanent GPS geodetic array) (Ibid, 2002). The number of GPS permanent stations in Southern California increased after the destructive Northridge earthquake in 1994 (Ibid, 2002). By the end of 1994, there were 5 stations established (Stone, 2007). It led to the establishment of the Southern California GPS Integrated GPS Network with several hundred continuously operating stations. This network has since been combined with the US National Plate Boundary Observatory (UNAVCO, 2008).

The widespread use of GPS globally as well as CORS network developments has led to a big change in geo-positioning technologies. The geocentric datum of GPS (WGS84) has influenced many countries to update their often non-geocentric national datum to align with modem, satellite based geocentric datums to avoid unnecessary transformations for local users involved with surveying and mapping. Permanent GPS networks are now also used for national geodetic reference, ionospheric and metrological research (Stone, 2007). National, homogeneous CORS networks also allow for new web based online processing services whereby users can submit via the Internet their GPS data to be processed with high accuracy and receive the result via email in a few minutes. Such services are gaining popularity in the geospatial community. Geoscience Australia with AUSPOS (Geoscience Australia, 2008) and the Natural Resources of Canada with the Canadian Spatial Reference System (National Resources Canada, 2008) are two such examples providing online GPS data processing. Chapter 4 CONTINUOUSLY OPERATING REFERENCE STATION (CORS) NETWORK

Over the past few years, the use of RTK GPS has increased in the field of surveying and mapping and other associated engineering fields. Increasing productivity with centimeter level accuracy is the main advantage when using RTK GPS. However RTK GPS has a limitation in baseline length that should not be extended to more than 10-15 km depending on conditions, time of day and algorithms used in the particular hardware configuration. The main reason is that distance dependant biases (orbit error, tropospheric and ionospheric refraction) will occur during the very rapid ambiguity resolution process (Rizos et al, 2004). The first CORS networks only provided data for post processing in combination with data collected by a roving user. The development of RTK GPS took advantage of this CORS infrastructure initially providing real time "single based" RTK positioning and later "network based" RTK GPS (Lacaphelle et al, 2002). Network-based RTK GPS would allow carrier phase based positioning techniques to extend the distance between reference stations and roving receivers to tens of kilometers whilst maintaining centimeter level accuracy in real time (Rizos et al, 2002). Some European countries have upgraded their CORS networks into RTK positioning services. Denmark with the density of 10-20 km and Germany (approx 30 km density) with the SAPOS service provide users with cm-level accuracy using a network RTK service across their entire country (Rizos et al, 2004).

In recent years, the development of Global Navigation Satellite Systems (GNSS) other than GPS has increased. Russia has announced that they will accelerate the implementation of their Glonass (Global'naya Navigatsionnaya Sputnikova Sistema) satellite navigation system from the existing 13 satellite configuration (June 2008) to provide a full constellation of 24 satellites by 2010 (Interfax, 2008). In addition, the European Union followed this high cost project with the Galileo civilian satellite navigation system that was proposed to be launched in 2008 (European Space Agency, 2005). Currently two developmental satellites are in orbit and the full constellation is projected to be operational by 2013. Meanwhile China has developed their Compass satellite navigation system initially with geostationary satellites which will be later augmented by a 30 Chapter 4 CONTINUOUSLY OPERATING REFERENCE STATION (CORSi NETWORK satellite medium Earth orbit, GPS-like constellation of navigation satellites. In future the combined configuration of navigation satellites will offer GNSS users at least 80 satellites for positioning applications on and above the Earth. (Roberts, 2005).

The CORS network and its RTK application can take advantage of this multi- constellation environment. For RTK, which relies on the on-the-fly ambiguity resolution algorithm requiring at least five visible satellites at all times, the more satellites available offers significant improvements to the reliability of this technique (Ibid, 2005). However, the CORS network will require hardware upgrades at each reference station to replace GPS only receivers with GNSS multi channel receivers to accommodate the GPS, Glonass, Galileo and Compass signals. 4.2. The Early Development of CORS Networks in Indonesia The development of CORS networks in Indonesia is quite slow before The Boxing Day Tsunami 2004. From the 17,000 islands that make up the Indonesian territory, only five stations have been established on five major islands as a part of the Asia Pacific GPS tracking station network. These stations are located in Medan (Sumatra), Kupang (North Timor), Bogor known as Cibinong (Java), Pare- pare (Sulawesi) and Biak (Papua). From these five stations, only Cibinong still operated continuously as a part of International GNSS Service (IGS) station (Matindas et al 2003).

Medan 1992 Bakosurtanal Operated, not continuous Exist Bogor 1992 Bakosurtanal IGS station, continuously operated Exist Pare-Rare 1992 Bakosurtanal Operated, not continuous Exist Kupang 1992 Bakosurtanal Operated, not continuous Exist Biak 1992 Bakosurtanal Operated, not continuous Exist

Table 4.1. Permanent GPS stations in Indonesia. Chapter 4 CONTINUOUSLY OPERATING REFERENCE STATION (CORS\ NETWORK

Present Status and Plan of (.ontimwns C>PS (cf^)

for Imloncshn Isunanii I{^r!y W;trnin^ System

- .J'

0'

-10' mmtmHirn *mmmiMm 1 95- 100' 105' 110" 115 120' 125 130" 135 140"

Fig. 4.1. Permanent GPS stations in Indonesia (Courtesy Bakosurtanal, 2009).

Table 4.1 and fig 4.1 show the number and the distribution of GPS permanent stations across Indonesia. After The Boxing Day Tsunami, there are in total 32 CORS station (2009) and 15 more soon will be operate These stations will potentially to be re-established as a fiducial network and as a framework for a higher density GPS network. Furthermore, if these stations can be operated continuously, they could form the backbone of a new CORS network across Indonesia.

A development of CORS networks in Indonesia is mainly for establishing the Sumatran GPS Array (SuGAr) project that started in 2002-2004. During September 2002 into mid 2004, 14 stations were successfully operated. A further 10 stations had been built after the large magnitude Aceh earthquake (SuGAr, 2005). This infrastructure was designed and maintained by the Indonesian Institute of Sciences (LIPI) incorporated with the Tectonics Observatory, California Institute of Technology. The objective of this project is to model and understand the characteristics of the large Sumatran fault (similar to the San Andres fault) by conducting research in paleo-geodesy and paleo-seismology around the fault. The fault is quite active with regular 7.5 magnitude earthquakes occurring around Sumatra. Fig 4.2 shows the configuration of the GPS network on and around Sumatra Island for the SuGAr project (Ibid, 2005). Chapter 4 CONTINUOUSLY OPERATING REFERENCE STATION (CORS) NETWORK

-m

^ IQ^ faiuit

cGPS . Sept 2002 (6) Aug 2005 (6) - K2 accelerometers May 2005 {4) stations (with . Aug 2004 (8) proposed 2006 (8) • High-rate cGPS (4) {with SOPAQ Instaliation , 2005 (4) carxJIdates, post-2006 (14) dates) • Nan-5«GAicGP5»aiiB»iit4) Vertical-comp seismometers May 2005 (6)

Fig. 4.2. Sumatran GPS Array (Ibid, 2005).

The Indonesian territory lies between two large continents (Eurasia and Australasia) and comprises many active volcanoes along the west coast of Sumatra and south coast of Java. These volcanic regions are "hotspots" for earthquake activity. The north coast of Sulawesi and the Moluccas archipelago are also active geodynamic areas. Ideally, Indonesia requires a high density CORS network widespread across these hotspots in order to better understand the cycles of geodynamic activities which could lead to early warning systems for local populations.

CORS networks have been established in many metropolitan and rural regions of developed countries where existing infrastructure is well established and stable. These modern CORS networks are used for various purposes (which strengthen the business case for establishing them) usually related to precision agriculture, mining, surveying and mapping applications. Ironically, countries that suffer earthquake and volcano hazards, which were the original beneficiaries of GPS research, could gain significant benefits from CORS network development however often do not due to funding constraints. Such networks benefit national Chapter 4 CONTINUOUSLY OPERATING REFERENCE STATION (CORS) NETWORK

geodetic infrastructure and thereby support Geographic Information System data acquisition, navigation, as well as local and central government data maintenance (Celik et al, 2006).

4.3. CORS Network Definition

Recently, the trend in surveying - in particular cadastral surveying - is to speed up the surveying process by replacing classical control networks with GPS reference station networks (CORS) (Harris, 2006). The term CORS was first used by the United States National Geodetic Survey (NGS) to support national coordinate system accuracy and consistency with a control network that can actively update user position (Stone, 2000). In the first development, CORS networks were passive networks that only logged data and archived it. In order to use the data, the archive needs to be published on the internet and available to download or the users have to make a correspondence to the authority for use of the data. The five stations (Medan, Cibinong, Pare-Pare, Kupang and Biak) as a part of Asia Pacific tracking station in Indonesia could be classified as a passive network.

The passive network changed into active network when the CORS network used a communication infrastructure (radio, VHF, UHF, internet and VSAT) for broadcasting the data to users. SAPOS in Germany and SydNet in Sydney basin are examples active networks. These active networks are able to support a new paradigm called "integrated surveying" whereby GPS RTK and Total Station technologies are combined by connecting to a surrounding CORS network with communications devices (wireless modem, or Internet) to deliver real-time GPS positioning which could be augmented with terrestrial techniques where skyview is limited. The active network is projected as a future network that will significantly reduce the current required density of conventional geodetic control points thereby reducing maintenance costs for national and state governments charged with the responsibility of maintaining ground marks (Ibid, 2006). Totally replacing the classical ground mark infrastructure is unfeasible as many issues Chapter 4 CONTINUOUSLY OPERATING REFERENCE STATION (CORS) NETWORK related to surveying regulations and acceptance of GPS derived positions by surveyors will remain. Indeed physical evidence of a landholders property will always give confidence in a trustworthy land administration system.

The development of a CORS network does not just provide real time services for positioning. Another important consideration is the ability of the network to actively update its position due to plate tectonic motion and account for this seamlessly for users. This capacity leads to a term called a "dynamic and active" CORS network. GPS networks in New Zealand are active - that is they are able to broadcast corrections in real time to users - as well as monitoring the deformation model related to how the island has moved due to the large active fault system running north-south down the country (Gledhill, 2004). Users receive coordinates which relate to the 2000 position of coordinates which are corrected with backwards velocity vectors computed by the CORS network tracking over time.

Willgalis et al (2002) stated that the benefits of using an active network, such as network RTK, for surveying applications shown below in table 4.2: C well suitable, 9 partly suitable. O uiisiutable) Survey method Post Processing Real Time Application Static, stop&go RTK network RTK rapid static kinematic Geodetic control sur\'eys • 0 • Netw^ork densification • 9 9 • Cadastral sun-eys 0 9 • Topographic sur\'eys 0 9 • Large scale mapping 0 9 9 • Sun'eying-in of buildings^ 0 0 9 • Setting out 0 0 9 • 1) in combination with electronic tacheometr>' Table 4.2. Suitable GPS positioning methods for certain survey applications (Ibid, 2002)

Interestingly, table 4.2 shows that network RTK could perform well in cadastral surveying and building surveys. However, this performance could not stand alone Chapter 4 CONTINUOUSLY OPERATING REFERENCE STATION (CORS) NETWORK

In order to stabilize the power supply and therefore data recording, an uninterruptible power supply (UPS) and generator are needed in case of power outages or power spikes which may damage sensitive electronic instrumentation (Stone 2006). Lightning protection is mandatory for reference stations.

4.3.2. Site Configuration

Celik et al (2006) identified some factors related to how to establish a good reference station site. The most important aspect is that the GPS antenna must be mounted on a stable site with a clear skyview. NASA's Jet Propulsion Laboratory (JPL) recommends that no obstructions at the reference stations site should be greater than 5 degrees above the horizon (Stone, 2000). A continuous, stable electricity supply should also be available at the site.

Stone (2006) added that site location will depend on the CORS network function. If the CORS network will be employed for supporting relative positioning for surveying and mapping, reference stations should be located in metropolitan areas and at sufficient density where most activity takes place. However if the CORS facilities are to be employed for precise satellite orbits and clock corrections, it is better to locate these facilities more widely relative to each other.

The other consideration in locating CORS facilities that are to be upgradeable into a network RTK capability is the availability of a suitable communication link. Rizos (2002) stated that in general, some communication options are suitable for network RTK such as a mobile phone standard data link or a dial up data link using a modem for a fixed station. In remote regions, Jackson et al (2002) also added that a satellite communication (VSAT) data link could be used. Therefore, the site for setting up these facilities must be accessible to transmit the correction data. Chanter 4 CONTINUOUSLY OPERATING REFERENCE STATION (CORSt NETWORK

for surveys in particular areas where multipath and signal blockages were the major obstacles. Therefore, a combination between network RTK GPS survey and terrestrial surveying by using Total Station or the other conventional survey methods (i.e SmartStation) is strongly advised (Leica, 2007). Indeed instrument manufacturers have tapped into this niche and provided instruments suitable for integrated surveying. Network RTK GPS is recommended for all applications given above, but again only where suitable skyview is available. More explanation about network RTK will be addressed in section 4.4.

Celik et al (2006) stated that a typical CORS infrastructure requires dual frequency, carrier phase GPS receivers, choke ring antennas, an uninterruptible power supply, data storage and radio communication. Generally, Stone (2006) divided the CORS components into three parts i.e. hardware configuration, site configuration and data management.

4.3.1 Hardware Configuration

The GPS receiver must be geodetic quality and capable of measuring P-code and C/A code pseudorange as well as LI and L2 carrier phase (Stone, 2000). With the reinvigoration of the Russian Glonass constellation and impending launch of both the European Galileo and Chinese Compass satellite navigation systems. Stone (2000) added that receivers must have the capability to collect all of the data available with the new GNSS signals.

For reducing multipath effects, Celik et al (2006) stated that a choke ring antenna should be used for this purpose. Some manufacturers have designed smaller antennas that could reduce multipath effects for the roving user. These are generally designed to be lightweight for usability in mobile applications. Choke ring antennas are heavy, unwieldy and expensive, but provide the very best data quality and are therefore used for reference stations only. Chapter 4 CONTINUOUSLY OPERATING REFERENCE STATION (CORS) NETWORK

Another consideration is the location of the site must be free from signal and pulse interference. Commonly, this problem comes from transmission facilities which can disturb signal reception (Stone, 2000). Klinker & Pietersen (2000) stated that the potential sources for GPS interference were Very High Frequency (VHF) / Ultra High Frequency (UHF) television broadcasters and Frequency Modulation (FM) radio transmitters with output power exceeding 50 kW. In addition the mobile satellite communication was also categorized as a handset that gave significant interference for GPS signals (Gromov et al, 1999). The next consideration concerns the security of the site. It must have limited access to the public to avoid tampering, vandalism or theft.

Cruddace et al (2002) suggests that there is a hierarchy of four main choices for establishing base stations.

1. First of all, the base station should be included in an existing national active GPS network. This is the easiest choice for converting these stations into RTK status later. 2. Secondly, choose common sites that are owned by two or more institutions. Some partnership between organizations which have the same vision in spatial technology will be an advantage for establishing common base stations. 3. The third is to locate reference stations at existing survey and mapping authority offices such as the local Department of Lands. Rental payment, which can be the largest on-going overhead for a CORS network, can often be considered an in-kind contribution to the project. 4. The last choice is a party site. This is the worst possibility due to the high cost that needs to be paid for ongoing rent at the site, communication permission, public permission/maintenance costs and safety considerations. Chapter 4 CONTINUOUSLY OPERATING REFERENCE STATION (CORS) NETWORK

4.3.3 Data Managenlent

The biggest issue related to data management is how to deal with the large volume of data. In the normal CORS operation, GPS receivers collect and record the data continuously. This requires high capacity storage. Celik et al (2006) specified that GPS receivers must be able to perform one (or even less than one) second data sampling, be capable to store the data, archive the data and provide data in RINEX format.

Generally, Cruddace et al (2002) made two definitions for data management due to their different function:

1. Data Manipulation For handling real time data with a single keyboard in a central computer terminal (hub). The hub must comprise a minimum of three servers for the hub's front end, a main processor and a communications (dial-up) processor. In case of any malfunction in this hub, there should be a back up system in place. 2. Data Broadcasting This segment deals with data correction delivery and delivery modes such as GSM, VHF and GPRS. Formerly, VHF was very common in data broadcasting, but there were some disadvantages in using VHF due to frequency traffic and interference. GSM evolved as another choice but the high cost for GSM was a prohibitive consideration as billing was calculated for the duration of the connection. The GPRS packet data service was wireless and charged for data volume (relatively small for CORS network data) and has become the next generation for broadcasting correction data. Chapter 4 CONTINUOUSLY OPERATING REFERENCE STATION (CORS) NETWORK

4.4. Network RTK Concept

The network RTK concept is an enhancement of a CORS network. Rizos (2002) stated that network RTK aims to achieve the same centimeter level of accuracy as single based RTK systems over longer baseline distances. Rizos (2002) estimated the distance between reference stations in network RTK should be 50-100 km. This depends on the site geographic location and level of ionospheric and tropospheric activity. At the equator, Willgalis et al (2002) in their network RTK research in Brazil, suggested that for achieving decimeter or even centimeter accuracy, the distance should be less than 10 km due to a heightened ionospheric activity in this region.

The key to success for network RTK is in resolving integer ambiguities correctly among multiple static reference receivers located at positions. Ambiguity resolution processing must be able to deal with double difference data from long inter station distances (approximately 50-100 km), then transmit the result in real time and with minimum delay (Ibid, 2002). Rizos (2002) also defined the services from network RTK messages below:

1. Orbit bias elimination and ionosphere delay estimation; 2. Troposphere reduction, multipath and observation noise mitigation; 3. Extending the range of reference stations into medium range (more than 100 km) 4. Single frequency receiver could be used for RTK and static positioning at medium range; 5. Giving the possibility for high accuracy applications such as deformation monitoring, geodetic control networks with cheap GPS receivers.

Wanninger (2004) stated there are three steps in network RTK data processing related to successful RTK positioning. First of all, the reference station network should be able to fix the ambiguities such that distance dependent biases could be Chapter 4 CONTINUOUSLY OPERATING REFERENCE STATION (CORS) NETWORK precisely modeled. Real time ambiguity fixing for widely spaced reference stations is the main challenge in network RTK.

The second step is estimating correction model coefficients. This step attempts to interpolate distance dependent biases between reference stations and user receivers. Therefore, in this process, each satellite must be modeled individually for its ionosphere and orbit biases. However, in this process, the main concern is that the ionosphere is unstable and changes relatively rapidly. Consequently, the ionosphere correction must be updated more often (up to six times more often) than troposphere or orbit corrections which are both considered less dynamic.

The third step concerns computing the reference observation from a selected master station (commonly the closest to the rover) and a determination of the distance dependent correction interpolated for the rover point. The rover receiver computes its position from the virtual reference station which appears to be made from short baseline processing.

4.5. Network Communication Concept

Network RTK requires real time communication to a network computing centre and estimation of biases. This potentially creates a large amount of data traffic in real time (Euler et al, 2005). Generating information within the network computing centre and sending to the moving GPS receiver in the field becomes the most important component in the network RTK operation for users (Ibid, 2005). Busies (2007) identified that, network RTK communication is divided into three categories. Each category has different characteristics as elaborated below.

4.5.1. Virtual Reference Station (VRS)

This concept uses two way communications between a rover and a central computing facility. First of all, rover stations have to send their approximate Chapter 4 CONTINUOUSLY OPERATING REFERENCE STATION (CORS) NETWORK positions (navigation solution only) to the processing centre. Then, atmospheric corrections for this nominal position will be generated and transmitted to the rover stations for baseline positioning. This transmission of corrected observation data uses the standard format of radio navigation and radio communication developed by the Radio Technical Commission for Maritime Service (RTCM). The message type is 20/21 or 18/19 (Leica, 2006).

This concept has been widely used for network RTK positioning due to some benefits in its operation. The processing centre computes and sends corrections based on an actual rover position. Wanninger (2004) identified that upgrading for user equipment is unnecessary. In addition, problems related to area identification to specify the rover point position could be ignored. This concept does not need a special format or conventions to be uploaded onto a user receiver (Leica, 2006). Significantly, there is a reduction in the temporal correlation of ionospheric residual errors as information is regularly updated in the field (Vollath et al, 2002).

There are some disadvantages in this concept due to quality control that could not be provided during the interpolation process and VRS reference observations. VRS may experience significant errors if the rover station moves too far from its original position (Busies, 2006). The other disadvantage is that the VRS computing and modeling is based on a specific user (point) not the VRS area (Retscher, 2002). So every point in the VRS area must be modeled. This can be problematic if a large number of users want to use the VRS simultaneously. Generally only a single user access a VRS solution based upon their rovers position. Though using a radio to rebroadcast the VRS can allow multiple users to access the same VRS. But typically it is one user per VRS. However multiple rovers (up to 1000) can be on the system generating individual VRS's at anyone time (dependent upon computing power). If a rover moves more than 5 km (by default) from their initial VRS position a new VRS is automatically generated. So if the rover moves 20 km from its original starting point throughout the course of Chapter 4 CONTINUOUSLY OPERATING REFERENCE STATION (CORS) NETWORK

the day or course of work being completed, then four individual VRS's are generated automatically as the rover moves (Asmussen, 2008).

Fig. 4.3. VRS concept (Vollath et al, 2002)

4.5.2. Area Correction Parameter (FKP)

FKP stands for Flachen Korrektur Parameter, or spatial correction parameter in English (Busies, 2006). This concept is mainly using RTCM as a communication format. The Bundesamt fur Kartographie und Geodäsie (BKG) (or German Geodetic Service) have standardized the messages which use RTCM 2.3 format by utilizing the unused message number 59 to transmit the FKP parameters to users. This convention has been applied across the SAPOS GPS network in Germany (Wubbena & Bagge, 2002). In this concept, correction for each reference station is determined by a processing centre. Parameters of an inclined plane should be modeled first for distance dependent corrections. In addition, plane parameters are calculated for the ionosphere free linear combination and the narrow lane combination for each satellite. Therefore distance dependent corrections could be determined in the case of LI and L2 frequency separately. Chapter 4 CONTINUOUSLY OPERATING REFERENCE STATION (CORS) NETWORK

More explanation about the ionosphere free hnear combination and the narrow lane combination will be addressed in chapter 5 section 5.2.1 and 5.2.2.

In contrast with VRS, this concept uses one-way communication. The rover station itself performs processing and corrections based on the received correction parameters and the different coordinates between the rover and reference station. Therefore, a motion dependence individual correction could be computed by the rover (Busies, 2006). In addition, this concept has no restriction to the number of participants and reference stations and is suitable for kinematic applications (Leica, 2006).

However, a long distance between reference stations is an obstacle with this concept. If the distance is more than 100 km, correction parameters are invalid (Busies, 2006). In contrast with VRS, FKP needs area identification and a special format and conventions. Additionally, rover side interpolation is required which means either a hardware or firmware (or both) upgrade for a user (Leica, 2006).

Fig. 4.4. FKP Correction Symbolization (Ibid, 2006) Chapter 4 CONTINUOUSLY OPERATING REFERENCE STATION (CORS) NETWORK

4.5.3. Master Auxiliary Concept

The first release of the Master Auxiliary concept (MAC) was in 2001 resulting from collaborative work between Leica Geosystems and GEO++ (Burbidge, 2006). The MAC concept transmits the main observation data and corrections to the rover in a compacted format (Euler et al (2001). The carrier of data transportation (raw and correction) uses the radio communication and navigation standard from the National Marine Electronics Association (NMEA). The MAC concept consists of a network that can be broken down into subsets called clusters and cells. The whole network is divided into clusters and each cluster contains cell networks. Sometimes, small networks just consist of one cluster. But for large networks, several clusters are needed to manage processing and data distribution. Master Auxiliary corrections in one cell are generated from one master station and a few auxiliary stations.

!/ •

À 2.çfM9t9r ^ t çli^t^r V A

Fig. 4.5. Cell and cluster system (Busies, 2006).

Leica's SpiderNet software uses the MAC concept providing several benefits such as no limitations on the number of reference stations. It means that users could use Chapter 4 CONTINUOUSLY OPERATING REFERENCE STATION (CORS) NETWORK the maximum number of reference stations that will improve a users' network geometry and estimate a large number of atmospheric effects. In addition, MAC will give more choice for users to choose good reference stations due to its availability and reliability (Ibid, 2006).

Auxiliary Reference Station C

Master Reference ^tion Rover User

X

uxiiiary Reference ®/ Station D

Auxiliary Reference Station B

Network Processing Auxiliary Reference Facility Station A

Fig. 4.6. MAC Concept (Burbidge, 2006)

Basically, the MAC concept is quite similar with VRS. The main difference is that MAC uses a real rover position. In general, the MAC process could be explained as such:

1. Network Processing Facility receives GPS raw data that has been transmitted by reference stations. 2. Network Processing Facility computes network estimation and ambiguity resolution. Chapter 4 CONTINUOUSLY OPERATING REFERENCE STATION (CORS) NETWORK

3. Rover receiver transmits its position via NMEA to Network Processing Facility. This includes determining suitable and nearest reference station. 4. The software computes network corrections and uses in observations via master receiver. 5. Network Processing Facility transmits the corrections using RTCM format or other data transmission format. 6. Real time and high accuracy position is computed using reference network and its corrections.

The important things to be concerned are that network RTK requires five common satellites as a minimum for rover and reference station observations. If this requirement cannot be fulfilled in one epoch of observations or the network does not get any network corrections, then network RTK positioning ceases to function. Some network RTK processing software such as SpiderNet are also able to generate a single baseline solution.

4.6. Communication Conditions in Aceh

In order for network RTK to operate, good communications for data traffic management for transmitting and receiving data is essential (Wagener & Wanninger, 2006). Internet connection, land line telephone and the other data streaming services are options for securing the communication link. Therefore communication plays an important role in the success of network RTK GPS operations. The cost of the communication was an important consideration when establishing network RTK. It was very expensive to get a fixed Internet Protocol (IP) address in Aceh. One fixed IP address would cost almost $AUD650. In addition, the cost related to the purchasing price for communication equipment (transmitter and receiver) as well as, if the communication would use mobile phone with a monthly cost and additional charges based on capacity of the data transfer would need to be considered. Chapter 4 CONTINUOUSLY OPERATING REFERENCE STATION (CORS) NETWORK

A common and easy data connection is via mobile phone that is offered by communication service providers. The general service is the oldest generation General Packet Radio Service (GPRS). It is quite common for Global System for Mobile Communication (GSM) with data rates from 56 to 114 kbps. The next generation of GPRS is the Generation (3G) and the High Speed Downlink Packet Access (HSDPA) that has transfer data rates of 42 Mbps. However the billing regime and therefore overall cost must be considered for all of these communication services.

The Boxing Day earthquake and tsunami destroyed existing communication infrastructure. Authorities were faced with two options to re-establish network communications. Either full land line operational installation for all communication networks could be re-established. This option would be expensive in hardware installation because it would need to re-install any hardware and software from the beginning. Most of the infrastructure was totally lost. Therefore, it is unlikely for telecommunication companies in Indonesia to commence large investment activities for hardware installation.

Alternatively, wireless infrastructure could be a more suitable choice. It is relatively easy to establish and install and does not need cable and other such hardware. For low cost telephone facilities. Code Division Multiple Access (CDMA) phone services had been implemented in some telecommunication products such as Telkom Flexi. In addition, a GSM telephone service is already capable with GPRS, 3G and HSDPA services. The common choice for wireless is a 2.4 GHz internet wireless connection which offers a maximum load of 10 Mbps (Riyadi, 2005). Nonetheless, this technology has difficulties with limited data load that only offers 10 Mbps. This data capacity traffic is unsuitable for supporting communication in all Banda Aceh regions. Furthermore, with only 2.4 GHz connection, the coverage area will be limited to a half of Banda Aceh. Chapter 4 CONTINUOUSLY OPERATING REFERENCE STATION (CORS) NETWORK

The Aceh Telco Relief project was a project that was funded by the Intel Corporation. This project's purpose was to re-establish information technology infrastructure after the earthquake and tsunami. Due to network stability considerations and the need for a widespread internet service and communication infrastructure, Wireless Broadband Access (WBA) BreezeACCESS VL (5.25- 5.35 GHz and 5.725-5.850 GHz frequency) was chosen as the best wireless internet solution (Ibid, 2005). The frequency was quite secure from interference and could overcome the topographic problem (many hills and valleys).

A iX " ' -

. ; V ' WP', . . yyp pOleelheue^ ' »WP ^• ' ' • /

Wf? • . '»WP i • WP

îmage.'^ 2008 DigilalGtobe x^x^BTS' Lambaro > # O 2008 Europâ Technologies

Pointer 5'32'40,49-N 95°20'14.S9-E etev 21 (t Streaming |j|j||j|!| 100% Eye alt 44806 (t

Fig 4.7. The configuration of Base Transceiver Station (BTS) towers and wireless points in the Banda Aceh region plotted in Google Earth (Aceh Media Center, 2005). Chapter 4 CONTINUOUSLY OPERATING REFERENCE STATION (CORS) NETWORK

The grand design for this infrastructure was to build three or four wireless base stations around Banda Aceh which would have 27 Mbps bandwidth with a range of 15 kilometres. Each base station would be directly connected to a fibre optic termination point near the Aceh coastline. In addition, for installation of 50 hotspots as primary targets, this project would also provide a Client Premises Unit (CPU) that would be installed in some public places and facilities such as offices, schools and universities requiring internet access (Ibid, 2005). Fig 4.7 presents the distribution of BTSs and wireless points that had been built since October 2005. The red circle denotes the BTSs installed in Lambaro, Tabina and Syah Kuala University. The yellow points represent wireless points that were mainly installed in public access areas which are not completely installed as per the scheduled 50 points.

Technically, this equipment was ready to install and to operate in a short period of time. However, there was another issue related to the regulation for frequency permission allowed in Indonesia. The regulation stated that operating WBA with a frequency of more than 5 GHz requires permission similar to those telecommunication operators or providers. Furthermore, annual taxes must be paid by the user of this frequency. Another obstacle was the high taxation to import WBA equipment into Indonesia. But the earthquake and tsunami recovery provided special circumstances such that all this equipment were allowed to be installed.

Chapter 4 has defined a CORS network. It has provided the history of CORS networks internationally and also specific to Indonesia. The concept of Network RTK has been introduced and the three major Network RTK techniques presented. The specific situation in Aceh particularly the communication condition after the earthquake and tsunami has been presented with reference to problems that will be encountered in this challenging environment. The following chapter will focus on the tropospheric and ionospheric delay that cause distance dependent biases which a network RTK algorithm must tackle in order to provide Chapter 4 CONTINUOUSLY OPERATING REFERENCE STATION (CORS) NETWORK reliable cm-level positioning for users. Issues specific to equatorial regions such as Aceh will be covered in more detail. Chapter 5 TROPOSPHERIC AND IONOSPHERIC DFIA Y

Chapter 5 TROPOSPHERIC AND lONOSPHERTC DELAY

The atmosphere contains various gases predominantly nitrogen (79%), oxygen (20%) and other gases (1%) (UTK, 2007). The Earth's atmosphere is divided into several layers based on physical properties and appearances, temperature, ionization and composition (see fig 5.1).

When using differential GPS techniques, after double differencing and successful anibiguity resolution has been achieved, the major distance dependent biases are due to the unpredicted ionospheric and tropospheric behavior. The GPS signal is an electromagnetic wave that is influenced by its propagation through the ionospheric and the tropospheric layers (see fig 5.1) causing time delays on the signal. The ionosphere is an electrically charged layer between 50-1000 km above the Earth's surface whereby free electrons are released due to solar radiation (Kolb et al, 2007). These free electrons interact with the GPS radio signals delaying the group velocity and advancing the carrier phase. The troposphere is a neutral layer extending from the surface of the Earth to between 10-16km and contains water vapour which also acts to delay the signal propagation.

Generally tropospheric models are used to account for GPS signal delay and for most applications are satisfactory for cm level positioning applications. The ionosphere is far more active and although models exist, they cannot account for the delay caused sufficiently to provide cm-level accuracy. For many applications (particularly RTK), these effects are simply ignored if the distance between the base and rover stations is kept small i.e. 10 km or less.

The effect of ionospheric and tropospheric delay is a minimum in the zenith direction from an observer location and is magnified as the local elevation angle approaches the horizon. Models incorporate a mapping function which Chapter 5 TROPOSPHERÌC AND IONOSPHERIC DELA Y

proportions the zenith path delay depending on the elevation angle of the receiver- satellite pair.

Ionospheric modeling also assumes a theoretical single, infinitesimally small layer where the entire ionosphere is contained at 350 km (see fig 5.1).

Ionosphere (Aurora)

Mesosphere

Fig 5.1. Atmosphere layers (UTK, 2007)

5.1. Troposphere

The closest layer of atmosphere to the Earth's terrain is the troposphere. This layer varies in thickness from approximately 8 kms at the poles to 18 kms at the equator whereby it changes into another distinct layer called the tropopause (ARIC, 2007). While the tropopause defines the top of the troposphere, in actual fact tropospheric refraction can still be present up to about , 40 km about the surface of the Earth (Leick, 2004). The temperature of the troposphere decreases with increasing altitude. There is a 6° C per kilometer decrease to almost -80° C above the equatorial region and approximately -50° C above the polar region. Chapter 5 TROPOSPHERIC AND IONOSPHERIC DELA Y

Most of the atmospheric mass, approximately 75%, is contained in the troposphere because almost all the atmospheric water vapour and moisture is found in this region.

Mendes (1999) and Schüler (2001) stated that the tropospheric refraction is divided into two parts; a dry or hydrostatic component and a wet or non- hydrostatic component. The hydrostatic component can be accurately modeled for the zenith path delay by measuring the pressure and temperature near the receiver antenna. This delay is usually about 2.4 m at mean sea level. The non-hydrostatic delay is caused by water vapour and is much more difficult to model. Any errors in tropospheric modeling arise from inaccuracies in determining the amount of water vapour in the column of air about the receiver antenna.

Brunner & Welsch (1993) illustrated the tropospheric delay as a function of satellite elevation angle and altitude of the GPS receiver. The refractive index can be defined as:

d.r.,„ = \{n-'i)-ds (1)

While the refractivity of troposphere:

(2)

Therefore, equation (1) can be re-written as:

d,' trap =.10-' trop (3)

The hydrostatic component (dry) and non hydrostatic component (wet) can be modeled as a tropospheric refractivity:

Hence, the total tropospheric delay consists of: Chapter 5 TROPOSPHERIC AND IONOSPHERIC DELA Y

(5)

The dry component comprises 90% of the tropospheric delay and the wet component is contained in the remaining 10%. Hofmann-Wellenhof et al (1998) developed an equation based on the integration of equation (4). Dry and wet refraction on the Earth's surface can be obtained by:

(77.64).^ (6)

=-(12.96).^ + (3.718X10-^}^ (7)

Where: p = pressure in the atmosphere (millibars) e = partial water vapor pressure (millibars) T = temperature degree (Kelvin)

Because the variation of troposphere depends on height, Hopfield (1969) also included a height factor as an additional parameter for empirical estimation:

hj-h ^Jn-.h ~ ^dn.O • (8)

Where hj =40136 + 148.72(7-273.16)

After combining with equation (4) and (5),

(9)

d, = ; , ' v^, (10) "" SinUE'-e.25) ""

Where E = satellite elevation in degrees. Chapter 5 TROPOSPHERIC AND IONOSPHERIC DELA Y

In addition, the wet component is hard to model because of the strong variations of water vapour in the atmosphere in space and time. The Hopfield model is used based on the similar assumption with the dry model (Rizos, 1997):

K-h N = M (11) h...

h^ is set between 11000 to 12000 m. So, the zenith wet delay is:

10"^ ^wet' ~ ^ -^wet^O-^w (12)

d^er = .d (13) Sin

The other alternative for troposphere is the Saastamoinen model (Seeber, 1993):

0.002277 1255 d,rop = P + + 0.05 .e-B.CorE (14) SinE

Where:

5.225 = (1-0.0026.//)

r = -6.5.//

H.(\+H/S)/8

100 r = e.

(7.5.//(238+/)) ^ = 6.107.10

A number of other troposphere models are available (Mendes, 1999), but most give similar results for surveying and mapping applications over medium baseline lengths (under 100 kms). Generally the models are either ignored or applied equally at both the base and rover stations during the double differencing process. Chapter 5 TROPOSPHERIC AND IONOSPHERIC DELA Y

The models can be less effective when a weather front is passing either end of the baseline or if there is a large change in height between the base and rover.

5.2. Ionosphere

GPS signals propagate from a satellite to receiver in approximately 0.07 seconds (Hada & Tanaka, 2004). During the propagation there is an interaction between solar radiation on the Earth's atmosphere and magnetic field (Marshall, 2000). Solar ultra violet radiation (UV) ionizes the atoms of the high altitude gases (above 80 km), freeing electrons. These charged particles interact within Earth's magnetic field and affect GPS signals by slowing down their propagation (or group) speed, while advancing their phase (Marshall, 2000). Increasing solar activity delivers an impact to ionospheric disturbances in Earth's atmosphere producing high variations in the spatial and temporal ionosphere (Janssen, 2003). The GPS signal can be delayed by 5-10 ns due to this ionospheric delay (Hada & Tanaka, 2004).

Ionospheric fluctuations are related to and depend on an 11-year solar cycle (fig 5.2) (Janssen, 2003). The density of particles in the ionosphere is denoted as foF2 and is closely related to the Sun Spot Number variations, particularly in the equatorial region (Xue & Boon, 2004). Chapter 5 TROPOSPHERIC AND IONOSPHERIC DELA Y

1850 1860 1870 1880 1890 1900 191Ì 1920 1930 1940 1951 DATE

300

Fig 5.2. Sun Spot Number variations (MSCF, 2007)

NASA (2007) defines the ionosphere as "a region covering the highest layers in the Earth's atmosphere, containing an appreciable population of ions and free electrons. The ions are created by sunlight ranging from the ultra-violet to x-rays. In the lowest and least rarefied layer of the ionosphere, the D-layer (around 70 km), as soon as the Sun sets, the ions and electrons recombine, but in the higher layers, collisions are so few that its ion layers last throughout the night."

National Geophysical Data Centre (NGDC, 2007) defines the ionosphere in layers with different characteristics. The closest region from the Earth is the D-region. This region has a distance between 75 and 95 km above the Earth and its main characteristic is weak ionization and high frequency wave absorption. From 95 to 150 km above the Earth, is the E-region that contains mainly ozone - 02^. The E layer is sub-divided into layers called E prefix (the thickest layer), E2 and the thin layer is a sporadic E.

Above the E-region is the F-region. The lower part of the F-region is comprised predominantly of the nitrogen oxide ion and the upper part is dominated by the O^ ion. This region is of primary interest for radio communication because of its Chapter 5 TROPOSPHERIC AND IONOSPHERIC DELA Y

importance in reflection of radio signals. Above the F-region, the highest region of the ionosphere is the topside region which has less influence on radio signals due to its weak ionization. This region mostly contains the O"" ion and some H^ and He"" which decreases in density with altitude from the Earth's surface. The topside region varies in height. Under normal conditions the height is about 1100 km but this can vary between 500 km at night and 800 km during the daytime.

ionized F-fayer The Atmosphere shuttle and the reflected short wave Earth-Space radio signals Interface northern lights

rocket loriized E~ layer View of the entire ainniospheric layer from the space shuttle Ionized D-Layer (courtesy of NASA) meteorite^. —i^ijiif weather spy plane balloon

Fig. 5.3. The Ionosphere layers courtesy University Corporation for Atmospheric Research.

The Department of Electronic and Electrical Engineering, University of Bath has examined the ionospheric structure using the same method as X-ray beams for medical purposes. However instead of X-rays, researchers have used radio waves directed into the Earth's ionosphere. This scanning procedure has delivered a 3D picture and animation of the ionosphere layers (Sunearthplan, 2007). Chapter 5 TROPOSPHERIC AND IONOSPHERIC DELA Y

Fig. 5.4. 3D Ionosphere Model (Ibid, 2007)

The composition and height of the ionosphere on each region depends on season, latitude, longitude, time, solar activity and geomagnetism (Hada & Tanaka, 2004). In addition, the magnitude of the delay on GPS signals depends on the Total Electron Content (TEC) and presence of ionospheric scintillations. Marshall (2000) stated that scintillation is short-term variations in the amplitude and phase ofradio signals travelling through the atmosphere. It can influence in quickening fluctuations of amplitude and phase from GPS signals. Ionospheric scintillations and TEC extremes occur mostly at the equator and in the polar regions. Leick (2004) gave the definition of TEC as a representative of the total amount of free electrons per 1 square meter column and giving a unit(lO'V//m^). Therefore, TEC is a description of the electron condition in the ionosphere.

The TEC equation is given by Leick (2004):

TEC = N^ds Jpath

Where: Chapter 5 TROPOSPHERIC AND IONOSPHERIC DELA Y

N^ = local electron density In addition, the ionospheric refractivity follows the rule:

40.30 ^^

«1 (16) f is the carrier frequency symbol (LI or L2). Since the GPS signal passes through the ionosphere, it follows the phase refractive index which consists of several components that are functions of some fundamental constants (Hargreaves, 1992).

n^ =^\-2N, =\-N, (17)

Then, from equation (16) and (17), the refraction index can be obtained from substitution:

^ do)^ ^ dO) df Where; n^p = phase refractive index n, = group refractive index CO = angular frequency / = frequency

Further simplification from equation (18) gives:

In fact, the o[n] ) value is very small and therefore could be neglected. Hence, the group phase velocity (c^) and {c^) will be denoted as: Chapter 5 TROPOSPHERIC AND IONOSPHERIC DELA Y

Because Nj is a positive number, phase velocity could be estimated to be higher than the speed of light in a vacuum. Therefore, group velocity would be the same value as Ac from equation (20) and (21) which is:

4030c Ac = cNj=—^N^ (22) /

The time delay in a GPS receiver of pseudorange or carrier phase is closely related to the difference in velocity and its variation. Further, the ionospheric distance could be defined by integrating equation (22) over time in metres.

p — 40.30c I path Ndte (23)

In addition, the relationship between distance and time along the signal path traveled could be defined as:

ds = c[\±N^)dt (24)

Again, N, is negligible due to its small value, then the inverse of equation (24) is defined as:

dt = -{\ + Nj)ds (25) c

Then, the ionospheric distance could be defined by substituting equation (23) and

(25) to give:

+ = (26) y2 hath ' Chapter 5 TROPOSPHERÏC AND IONOSPHERIC DELA Y

The integral related to the TEC value as shown in equation (15), thus becomes:

(27)

Where TEC is in units of electrons I m^ i is in units of Hz.

Finally, ionospheric time delay is defined as;

Ik.fP _ 4030TEC = (28) c ~ cf

The use of single frequency GPS only and TEC models removes 25-50% of the daily ionospheric biases (Rizos, 1997). Because of its error variation, errors can reach tens of metres. An alternative, and superior technique, uses dual L-band frequency GPS receivers. An ionosphere free combination of LI and L2 signals and a narrow-lane combination provide a dual band solution for removing the ionospheric effect. These techniques are used in the FKP solution for network RTK.

5.2.1. Ionosphere Free Combination

The ionosphere free combination is also known as the "L3" combination (Rizos, 1997). Its purpose is to model and eliminate the ionospheric delay on GPS signals by combining phase or pseudorange data from LI and L2 (Hofmann-Wellenhof, 1998). Rizos (1997) gave the equations for the ionosphere free combination based on LI and L2 functions in carrier phase and pseudorange measurements.

L3[[L\)cycles\ - 2M6L\[[L\)cycles\-\.9UL2[[L2)cycles (29)

Measured in L2 wavelength is:

L3[[L2)cycles] - \SUL\[{L\)cycles\-\ML2[[L2)cycles (30) Chapter 5 TROPOSPHERIC AND IONOSPHERIC PEIA Y

The ambiguity (/I3) that related to the LI and L2 ambiguities and can be modeled

as:

n-. {L\)cycles\ = 2.546/1, -1 MAn. (31)

n-. lL2)cycles\ = 1.984«, -1 Mn^ (32)

Where:

2 2.546 -

-1.984 - -/1/2 f'-h' 2 -1.54 =

In addition, the ionosphere free combination of pseudorange is derived below:

+ (33)

PiL2)=P + dio.(L2) (34)

Where: p = geometric range of the satellite at the time of signal transmission and the receiver at the time of signal reception.

The equation (33) and (34) then multiply by frequency squared the differencing would give:

f'An)-f2AL2) = (/,' + (35)

The last term of equation (35) is close to 0 and can be neglected: Chapter 5 TROPOSPHERIC AND IONOSPHERIC DELA Y

P - ^ - Al2) ^^^^ -P TT—1 (36) J\ Ji

The ionosphere free combination is quite effective at removing ionospheric delay from measurements but can not handle large scintillations. The result of this linear combination is a noisier solution. It was generally used for static baseline processing for distances greater than 10-15 km. It has been shown to be very effective in removing ionospheric effects (Hoffmann-Wellenhof, 1998). In equatorial regions it should almost be mandatory to use this combination as even short baselines suffer due to ionospheric disturbance (Roberts, 2002).

5.2.2. Narrow-Lane Combination

The other concept for removing ionospheric errors is the narrow-lane combination (L6). The error is removed by adding the 2 phase equations in LI and L2 expressed in cycles (Rizos, 1997):

0{n)+(l>{L2) = ^iL6) = •P-^{frdion(u)+f2'^ion{L2))+ni + n^ (37)

The ambiguity ) ^^ integer, so it has to be multiplied by wavelength (A^).

—^^—-0.11m (38) ' /,+/2

(39) J2

The narrow-lane combination has very low noise, however, the ionospheric effect is about 1.28 times that LI (Ibid, 1997). In addition, the narrow-lane phase is advanced by the ionosphere because the phase-range is too short. Chapter 5 TROPOSPHERIC AND IONOSPHERIC PEIA Y

5.3. TEC Map

The TEC data is useful information, in particular for satellite navigation, to apply the estimated ionospheric correction (The Australian Space Weather Agency, 2007). The global TEC condition could be identified through the TEC map in a real time mode using GPS observation data which were collected from ground stations. The computation of precise ionosphere maps is designed for navigation systems, monitoring ionospheric storm activity and ionospheric weather prediction (JPL, 2007).

A TEC map can be plotted based on TEC data for a particular epoch which is available in Ionosphere Map Exchange (lONEX) standard data format (Schaer et al, 1998). This data is available free for download at the IGS website (http://igscb.jpl.nasa.gov). The lONEX data can be plotted to construct a TEC map using any particular software.

The Leica SpiderNet QC software also provides a facility for plotting the TEC map (based on global data). This TEC map represents TEC conditions all around the world and not only in any particular area and the estiamted accuracy is not clearly stated. For the "Temporary CORS Network" project in Aceh, where the survey was done on 7 May 2007 (1427 GPS week), some lONEX data were downloaded since 02.00-12.00 UTC time which corresponds to 9am - 7pm with 2 hour intervals to see the situation in Indonesia roughly. Chapter 5 TROPOSPHERIC AND IONOSPHERIC DELA Y

Fig. 5.5. TEC Map at 02.00 UTC, 7 May 2007.

The TEC value is represented within elW in 0-90 scale. The low TEC value is represented by 0-20. Around 45 is the medium and around 90 is the highest value which means it will give a serious impact in ionospheric refraction. The TEC map above indicated that the highest value of TEC (shown in green) commonly occurred near the equatorial region during the day. Fig 5.5 mapped the condition at 02.00 UTC (or 9am in Aceh) at the beginning of the observation. At this time there was a small value of TEC around Indonesia and Banda Aceh. The highest was in east Indonesia, near the Pacific. Chapter 5 TROPOSPHERIC AND IONOSPHERIC DEIA Y

Fig. 5.6. TEC Map at 04.00 UTC, 7 May 2007.

The TEC value in the second map was recorded at 1 lam local time and started to reach a high value in the equatorial region particularly in around Indonesia. The value of TEC increased dramatically to about 45 (in green area) for the whole of the Indonesian region. Chapter 5 TROPOSPHERIC AND IONOSPHERIC PEIA Y

Fig. 5.7. TEC Map at 06.00 UTC, 7 May 2007.

The high value of TEC increased (green area) at 1pm local time particularly in western Indonesia, i.e. Java, Sumatra and Kalimantan. However the TEC value in eastern Indonesia remained relatively stable. Chapter 5 TROPOSPHERIC AND IONOSPHERIC DELA Y

Fig. 5.8. TEC Map at 08.00 UTC, 7 May 2007.

By 3pm, the amount of TEC decreased across most of Indonesia as can be seen in fig 5.8, however western Sumatera still recorded relatively high TEC values. Chapter 5 TROPOSPHERIC AND IONOSPHERIC DELA Y

Fig. 5.9. TEC Map at 10.00 UTC, 7 May 2007.

Even at 5pm local time as the majority of the high TEC region traveled west, half of the Indonesian region, particularly in the west, still experienced high TEC values. Chapter 5 TROPOSPHERIC AND IONOSPHERIC DELA Y

Fig. 5.10. TEC Map at 12.00 UTC, 7 May 2007.

As can be seen in most TEC maps, the TEC value would reach a peak in Indonesia, particularly Aceh (the location of the project), around 1 lam until 3pm. The TEC value increases concurrently with increasing the solar activity.

5.4. Special Behavior of Ionosphere and its Visualization on the Equator

The ionospheric conditions in equatorial regions represent special behavior. Large ionospheric fluctuations occur commonly in the ± 20° band either side of the equator and causes serious electromagnetic wave time delays (Fujieda et al, 2004). Recent research from the University of California, Berkeley showed that fluctuations in the air were generated by thunderstorm activities in the equatorial region (Steigerwald, 2006). This fluctuation will not directly affect the ionosphere, however change the structure of the E layer of the ionosphere, particularly during the day. NASA's Imagery sensor recorded 30 days atmospheric data from March 20 to April 20, 2002. Chapter 5 TROPOSPHERIC AND IONOSPHERIC DELA Y

Fig. 5.11. A false color image of ultraviolet light in the ionosphere that encircles the Earth (Steigerwald, 2006)

Fig 5.11 shows that the white and blue lines that encircle the Earth along the equator indicate ionospheric activity in a pair of thin bands with some portions appearing more dense than the average. The brightest lines (showing the greatest ionospheric activity) were located in three pairs over the tropical rainforest along the equator at: Indonesia in South East Asia, the Amazon Basin in South America and the Congo Basin in Africa. Another line pair is located over the Pacific Ocean.

This phenomenon gives further evidence that the ionosphere exhibits a special behavior in equatorial regions that affects GPS signals traveling from GPS satellites to a receiver. Besides the high evaporation processes, the major thunderstorm activity also impacts the changing ionospheric structure. Chapter 5 TROPOSPHF.RIC AND IONOSPHERIC DFIA Y

5.5. Geomagnetic Storm

Geomagnetic storms are a temporary disturbance in Earth's magnetosphere that is caused by disturbances in space weather. The disturbance is caused when the Sun releases a bubble of ionized gas which impacts the Earth with a spread energy known as a Coronal Mass Ejection (CME). The energy released carries up to 10 billions tonnes of plasma and travels with a maximum speed of 2000 km/s (Phillips, 2000).

During periods of maximum solar activity, a geomagnetic storm would influence ionospheric electron content (Odijk, 2001). The storm could degrade the accuracy of GPS single point positioning (Kunches, 2000). Moreover, geomagnetic storms in equatorial regions are more likely to cause heightened ionospheric scintillation activity and therefore degrade the GPS signal propagation (Skone & de Jong, 2000). The magnitude of a geomagnetic storm is measured using the Kp index (Planetary K-index) and is computed every 3 hours and published along with the other parameters in the NOAA Space Weather Prediction Center (www.sec.noaa.gov).

Generally, geomagnetic storms are categorized into a 5-step scale based on its Kp index value as seen below: Scale Description Kp Index Number of Storm G5 Extreme 9 4 days per cycle G4 Severe 8 including 9- 60 days per cycle G3 Strong 7 130 days per cycle G2 Moderate 6 360 days per cycle G1 Minor 5 900 days per cycle Table 5.1. Classification of Kp Index Value (www.sec.noaa.gov) The fieldwork for the "Temporary CORS Network for Land Reconstruction in Aceh, Sumatera" project was conducted in May 2007. On 7 May 2007 there was a GPS survey to establish reference stations. The project was located in the Chapter 5 TROPOSPHERIC AND IONOSPHERIC DELA Y

equatorial region. The TEC ionosphere map and Kp index value can therefore be used to indicate the likelihood of any influence from geomagnetic storms.

Estimated PlaneUry K index (3 hour data) Begin: 2007 May 5 0000 UTC

May 5 May 6 May 7 May 8 Universal Time Updated 2007 May 8 02:45:03 UTC NOAA/SEC Boulder, CO USA

Fig. 5.12. Kp Index on the day of survey, 7 May 2007 (www.sec.noaa.gov)

Fig 5.12 above shows the value of Kp index from 5 May 2007 00.00 UTC time until 8 May 2007. The Kp index during 7 May 2007 was quiet and fluctuated between values of 1-5. The highest Kp index value of 5 was experienced around

18.00 UTC time. This value could be categorized as a minor Kp index which means that there was no serious impact from TEC during the survey.

Chapter 5 has addressed the physical structure of the atmosphere as well as tropospheric and ionospheric refraction. This is quite important as the "Temporary

CORS network" project took place in the equatorial region. Furthermore, the TEC map based on the lONEX data and Kp index value was presented on the particular Chapter 5 TROPOSPHERIC AND IONOSPHERIC DELAY

time of project. Chapter 6 will continue the discussion about the fieldwork that took place in Aceh. Chapter 6 FIELDWORK IN ACEH

Chapter 6 FIELDWORK IN ACEH

There are estimated to be more than 10,000 land parcels that were destroyed over a large area as a result of the Boxing Day earthquakes and tsunamis (Benny et al, 2006). Single based RTK was used for re-survey and re-coordinating of land parcel boundaries but had a limitation due to the distance between the reference and rover receiver. This limitation was mainly caused by distance dependent errors that limit the inter receiver distance to not more than 10 km to ensure quick ambiguity resolution (Rizos et aU 2003). In addition, geographic conditions such as the many hills and valleys presented an obstacle for single based RTK.

Network RTK could provide coordinates to rover users with the capability of determining static and real time positions in 1-2 minute intervals, with more accuracy and increasing reliability (Uzel & Eren, 2006). The possibility of using network RTK in land reconstruction is possible due to the large number of land parcels that need to be measured, hi addition, Janssen (2003) identified that the more active ionosphere is the main obstacle for single based RTK in the equatorial regions over extended distances. Network RTK accounts for ionospheric disturbances. Therefore baseline lengths between a reference station and a user can be longer compared to single base RTK whilst still maintaining cm-level accuracy.

The preliminary temporary CORS network concept had a benefit of being an independent network (or cell) with its own central computing facility and required to communicate with its reference stations and users without the need to connect to an external internet network. This obviously presented significant advantages for disaster stricken regions such as Aceh. The whole single cell network could "leapfrog" to a neighboring cell network to continue operations. Chapter 6 FIELDWORK IN ACEH

Utilizing network RTK for land reconstruction would provide many benefits due to the large area that can be covered, overcoming higher equatorial ionospheric activity and providing positioning solutions in real time at centimeter level accuracy (Willgalis et al, 2002). On the other hand, real time communication and correction which was the key to success in network RTK (Euler, 2005), became difficult to fulfill due to the lack of infrastructure in this remote area.

6.1. Temporary CORS Network for Land Reconstruction

A few years ago, after the Katrina storm hit Louisiana in 29 of August 2005, most of the city was seriously damaged. The idea of a temporary CORS network was suggested when some surveyors wanted to stake out the elevations for relief purposes. Some problems included disturbed or destroyed United States National Geodetic Survey (NGS) benchmarks for surveyors (Cavell, 2006). The other reason for deploying a temporary CORS network was the large amount of land subsidence after the storm.

Cavell (2006) stated that the GULFNet 75 km spacing CORS network had been set up by the Centre for Geoinformatics, Louisiana State University in Louisiana. However, after the devastating storm, surveyors needed a higher density network. Strong networks with approximately 35 km spacing across the state would make the relief reconstruction project easier. In this case, CORS networks with daily positions calculated had been used for a better reference to detect the land subsidence after the storm and flood.

In addition, GULFNet was used to define the changing elevation of the land. The cost for conventional geodetic leveling had been reduced by operating this network. Formerly, it took US$1500 to US$2000 per mile and cost US$16 million for primary state control. Increasing the number of CORS network reference stations would reduce the cost for base flood elevation mapping by approximately US$50 million across the state (Ibid, 2006). Chapter 6 FIELDWORK IN ACF.H

Aceh was a similar case to Louisiana in terms of land reconstruction. Temporary CORS networks were quite relevant for supporting this project. In addition, land subsidence and ground surface displacement caused by the earthquake were also a large and ongoing problem. Horizontal movements at the sub meter level and vertical movements at sub centimeter level (Meilano et al, 2005) required many control points to be re-surveyed.

According to Benny et al (2006), some other considerations concerned with the re-survey and re-coordinating in land surveys for land reconstruction include:

1. Almost all affected parcel boundaries did not have coordinates in a global system. It would be very difficult to re-survey using GPS. 2. Large numbers of cadastral monuments which were directly related to cadastral boundaries were destroyed during the earthquakes and tsunamis.

This problem presented an opportunity for future geodetic networks linked to the cadastre providing a foundation for developing a spatial data infrastructure (Wanninger, 2006, Zhang et al, 2001; Brown et al, 2002; Rizos et al, 2003). In addition, large deformation from earthquake activity is required to be monitored by using a reference frame in a global datum. Such a proposal is controversial as it suggests replacing ground mark infrastructure with coordinates from satellite measurements. This is in direct contravention of the fundamental cadastral principle of "monuments over measurements", but given the unique circumstances in Aceh and the unfortunate likelihood of such an event re-occurring, such a step would be prudent (Blanchfield and Elfick, 2006).

Challstrom (2003) suggested temporary CORS networks should have 72 continuous hours of data for the computation of coordinates for the permanent reference points. These reference stations must be connected to the global International Terrestrial Reference Frame (ITRF). Recently, some organizations Chapter 6 FIELDWORK IN ACF.H

provided a facility to send GPS data to be processed into ITRF coordinates (Geoscience Australia, 2008; National Resources Canada, 2008) (i.e. AUSPOS and NRCAN discussed earlier in chapter 4 section 4.1).

6.2. Temporary CORS Network Fieldwork

The temporary CORS network in this project was established in cooperation with the RALAS project which was run by BPN and the World Bank. Three Leica GPS System 500 receivers and two Leica GPS System 1200 receivers were used in this exercise. The scenario was that four receivers act as reference stations and one receiver acts as a rover. The service from AUSPOS (2007) was used for processing reference station coordinates and the Leica SpiderNet software was used for the network RTK simulations and testing in a post process mode.

Fig. 6.1. Leica GPS System 500 and System 1200 (Leica, 2007)

As a planning component, a flow chart diagram had been made as a guide for the fieldwork. The flow chart included some processes during the preparation, data capture and then data processing. Chapter 6 FIELDWORK IN ACEH

Fig. 6.2. Flow chart for the fieldwork and data processing.

6.3. Survey Planning and Assessment

Ideally, this project seeks to set up a complete temporary network RTK system that operates four reference stations as mentioned in the flow chart. However, Chapter 6 FIELDWORK IN ACFH

there were many obstacles for setting up all the contributing items of equipment due to the difficult conditions in Banda Aceh. Surveying with five GPS receivers simultaneously required many logistics to be fulfilled. Initially this project planned to run with four reference stations and one rover receiver. 24 hour GPS observations would be observed at the four reference stations and the rover receiver would conduct a static survey at five different points during three different sessions (morning, afternoon and evening). Due to power supply problems only three reference stations were established and all measured for 24 hours although Challstrom (2003) suggested for 72 hours.

Related to power supply problems, some back up power was prepared. Running 24 hour observations required a continuous power supply. The main power supply for reference stations was from the mains electricity. However, due to the instability of power in Aceh, some back up or energy storage and adapter was deployed. An external battery (12 Amp accumulator cell) was connected as a back up power supply and an Uninterruptible Power Supply (UPS) was used.

Fig. 6.3. UPS and accumulator (pictures courtesy of Wikipedia, 2008).

6.4. Site Selection and Skyplot Analysis

Site assessment had been completed before the static observations at the reference stations. Considerations for site selection included skyview, stability of the mark/monument, power supply and site security. Initially it was planned to Chapter 6 FIELDWORK IN ACEH

establish four reference stations with one rover receiver. The unstable power supply was the reason for one reference station to be abandoned in favor of another location. One reference station failed to operate because the power supply was shut down for niore than 24 hours which was more than any of the backup systems could handle. Consequently, there were only three reference stations. The assessment of reference stations had been done based on some assessment items categories as can be seen in table 6.1. The red highlighted column denotes the failed reference station.

Mounted on pillar No Yes No Yes Stable and strong structure Yes Yes Yes Yes 5° elev free of obstruction Yes Yes Yes Yes Continuous power supply Yes Yes Yes No Conmiunication link Yes Yes Yes Yes Internet connection No No No No Signal interference Good Good Good Good Site security Good Good Good Good Located on point Yes No No No Multipath Good Good Good Good Reserve power supply Yes Yes Yes Yes

Table 6.1. Assessment of reference stations.

The first site reference station was Khaju. It was located near a BPN office for security reasons. This station was on the border of Banda Aceh and Aceh Besar and it was about 1.24 km away from the Indian Ocean. The point could not be mounted on the roof because of skyview obstructions near the site. It therefore had to be established using a tripod. The second station was approximately 1 km from the city centre and was located about 3.93 km from the Indian Ocean. This station was marked as GH and could be mounted on the roof of a building. The GPS antenna could be set up on the stable concrete roof and did not need a tripod. The last station was Lhoknga. This station was set up on a tripod and could be set up on the roof. The receiver must be set up with a tripod because if it was set up directly on the roof, the obstruction was quite bad. It was located about 20 km to Chapter 6 FIELDWORK IN A CEH

the south west of Banda Aceh and within 1 km from the Indian Ocean. Lhoknga was located in a region with the worst impact from the earthquakes and tsunami.

Survey planning was done before the reference station observations. In the Khaju reference station, planning using a skyplot diagram had been used based on approximate Khaju position and 15 degrees elevation mask angle. The skyplot diagram is a space diagram that is used to predict the satellite track based on approximate GPS receiver position and the current satellite almanac. The purpose of the planning was to assess the availability of common satellites between reference stations and the rover receiver during the survey on 7 May 2007 from 9 am to 7 pm (see fig 6.4).

Another consideration during the survey planning stage was the Dilution of Precision (DOP) value and the satellite availability. The DOP indicates the constellation and network geometry between satellites and the GPS receiver. A low DOP value indicates that there is a good constellation geometry between the satellites and GPS receiver. Satellite availability displays the number of satellites that a receiver could "see" during the survey. This survey planning used skyplot software that required an approximate position of each reference station and mask of angle that would be used during the survey as an input. The output of the planning was a skyplot diagram, DOP diagram and satellite availability diagram (see fig 6.5). Chapter 6 FIELDWORK IN A CEH

Fig. 6.4. Sky plot diagram for Khaju site. Cut off angle 15°, 9am - 7 pm in May yth Chapter 6 FIELDWORK IN ACEH

02 00 02:30 03:00 03:30 04:00 04:30 05:00 05:30 06:00 06:30 07:00 07 30 08:00 08.30 09:00 09:30 10:00 10:30 11:00 11:30 12:'00

UTC Time HDOP VDOP PDOP GDOP

Fig. 6.5. DOP estimation for Khaju site. Cut off angle 15°, 9am - 7pm in May 7

Fig 6.5 shows how the DOP value fluctuated but was never more than 6 which is satisfactory. The average DOP value during the day was usually below 4. The highest DOP value occurs between 2 - 2.30 pm and again at 3.30 pm and 4.30 pm. Chapter 6 FIELDWORK IN ACEH

03:00 04:00 05:00 06 00 07:00 08:00 09:00 10:00 11:00 12:«

UTCTime Fig. 6.6. The satellite availability for the Khaju site in May

The availability of the satellites in Khaju site is shown in fig 6.6. The satellite availability was generally 7 and above except for a short period at around 3-4 pm local time with only 5 satellites visible. This is the minimum required to allow computation of the network RTK correction. The maximum number of satellites (up to 12) was during 12 noon-1 pm, which coincides with the most active time for the ionosphere.

The similar skyplot analysis was done for the other two reference stations. The results were very similar to the Khaju station. Therefore, there should be no problem with common satellite availability across the network.

6.5. Common Satellite in Survey Planning

The ambiguity resolution is key to the success of network RTK GPS performance. Therefore, the ambiguities between the reference stations must be fixed first before atmospheric parameters can be computed to assist RTK positioning within Chapter 6 FIELDWORKINACEH

the network. In addition, the availability of satellites at all reference stations and the user must be kept to a maximum. For network RTK GPS a minimum of five common satellites at each reference station is required.

As the Aceh network comprises short baselines all satellites should be in view at all stations. Therefore a skyplot from one station was valid for all stations. Therefore, theoretically, the network RTK processing should be able to produce network corrections.

6.6. Problems Identification

The problems during field work could be classified into three categories namely hardware problems, security problems and power supply problems. Firstly, hardware problems related to the data storage on the GPS receiver. 24 hour observation files at a reference station at a one second sample rate required a large capacity of GPS data storage. Commonly, compact flash (CF) was the main data storage for Leica GPS System 500 and System 1200 receivers. System 500 had 8MB CF capacity and system 1200 had 16MB CF capacity. This CF memory capacity was not enough for 24 hours of GPS data observation storage. These CFs needed to be replaced with a higher memory capacity. The problem was that the availability of CF with fewer than 512 MB was an old version and very limited in the electronic market. In addition, the GPS receiver's operating system could not read the CF with 1GB or more capacity memory that was very common in the current electronic market. Chapter 6 FIELDWORK IN ACEH

Fig. 6.7. Compact flash and its adapter.

The security of setting up GPS receivers during the survey was a major concern. The GPS receiver must be safe from vandalism and other environmental hazards. Reference stations should be located near or within the compound of a BPN office. Nevertheless, hourly security checks were carried out in order to ensure the security of the receiver, a continuous power supply and that the receiver was consistently receiving GPS signals. Operators were supplied a check book to fill out every hour. The local environment must also be considered. Equatorial regions experienced high temperatures and high rainfall. During the survey, all equipment had to be waterproofed or covered and not allowed to get too hot. Leica states that the receiver should work properly in the range of temperature - 45 to + 65° C (Leica, 2007). The final problem refers to the availability of power supply. The complete explanation is stated in section 6.4

6.7. GPS Static Survey

Communications between GPS receivers was anticipated to be the main obstacle for real time network RTK operations in this research. Because of installation permission, limited time for the study and funding issues, the temporary CORS network would be a network RTK GPS simulation using previously logged static data at the three reference stations and five rover points logged simultaneously in a rapid static survey at three different observation times; morning, afternoon and Chapter 6 FIELDWORKINACEH

dusk. The sample rate was 1 second and the elevation cut off was 15°. Real time communications issues could therefore be ignored and network RTK GPS would be simulated using SpiderNet's network RTK GPS processing software in post processing mode. The real-time communication issues were not considered as the focus of this project.

The preparation for the fieldwork mainly dealt with the logistics relating to mobilization of field parties during the survey. Each field party had to ensure that all gear such as the GPS receivers, batteries and tripods functioned properly and continuously as well as filling out log books and storing data. The roving team had to ensure that they visited and revisited the correct points at the correct time. Chapter 6 FIELDWORK IN ACEH

Fig. 6.8. Reference Points (yellow stars) and rover survey marks (blue squares) overlaid on Google Earth and the damaged coastline (insert courtesy Benny et al, 2007)

Fig 6.8 represents the location of the three reference stations. The three reference stations were set up near the worst affected areas surrounding Banda Aceh. For safety reasons, GPS receivers were located near government offices either in the compound or preferably on the roof due to improved sky view. The distances between the three stations vary from 5 km to almost 20 km. Generally, the distance of reference stations in network RTK could be extended to tens of kilometres. However, in equatorial regions, ionospheric errors on the GPS signals restrict the baseline length even for network RTK operations. In the Singapore reference stations network, the distance between reference stations is less than 40 km (Rizos and Han, 2002) meaning that the distance between a rover and the nearest base station is never more than 20 kms. Chapter 6 FIELDWORKINACEH

Looking at fig 6.8 it was clear that the geometry of the network was poor (i.e. long and thin). This mainly had resulted due to the overwhelming logistical constraints, the shape of the damaged coastline, the location of the major activities in relief land reconstruction and the location of suitable sites for both GPS observations ,and security. The insert in figure 6.8 showed the damaged coastline in the Aceh Province, Regarding the five "rover" marks, two points were located inside the network and three outside the network. These rover points were located on BPN cadastral control points and Bakosurtanal geodetic control points.

Only the GH reference station was well mounted on a concrete roof for stability as well as avoiding tripod centering and maximizing skyview. The other two stations both required tripods because it was impossible to mount them on concrete due to their surrounding environment. Two Leica GPS system 500 with AT 502 antennas were used in GH and Lhoknga and a Leica System 1200 with LEIX 1202 antenna in Khaju.

Fig. 6.9. Pictures of Reference Stations, Khaju, Lhoknga and GH Chapter 6 FIELDWORK IN ACEH

During the preparations for the fieldwork, it was anticipated that working in Aceh would be extremely challenging and that trying to log useful GPS data and in real time would be unfeasible. Therefore, only static GPS data was logged and this data will be reprocessed in simulation mode using the Leica SpiderNet software. Results of this processing are given in chapter 7. Chapter 7 NETWORK RTK SIMULATION

Chapter 7 NETWORK RTK SIMULATION

This chapter will discuss the results of GPS data processing, the network RTK simulation and comparisons and analysis of these results for the Aceh data. Then in the next session, it will compare the network RTK simulation from the well established network RTK infrastructure in Singapore.

7.1. Network RTK Simulation in Aceh

7.1.1 Reference Point Computation

Dawson (2001) stated that internet web based GPS services have been developed to process coordinates in a global datum. AUSPOS (AUSLIG Online GPS Processing System) is one such service offered by Geoscience Australia. In early 2000, Geoscience Australia (GA) (formerly called the Australian Surveying and Land Information Group (AUSLIG)), developed the AUSPOS service to provide Geodetic Datum of Australia 94 (GDA94) coordinates for Australian users and ITRF based coordinates for worldwide users. Therefore this service could be used for global datum connection when deploying temporary CORS networks. However, it must be noted that the ITRF coordinate system was defined at a particular epoch in time. Anticipating this misconception, the ITRF coordinate must be transformed into the Indonesian coordinate system used for cadastral purposes if it would be used in the Indonesian cadastral system.

Reference station data was processed using the AUSPOS online service. This service is available for submitting dual frequency GPS data from anywhere on the Earth (Dawson et al, 2001). The AUSPOS processing uses ITRF2000 coordinates at contributing IGS reference stations which surround the user data. In addition, the International GNSS Service (IGS) product (satellite ephemeris and earth Chapter 7 NETWORK RTK SIMULATION

orientation parameter) in ITRF2005 is used for users who submitted their data after Saturday, 4 November 2006 (Geoscience Australia, 2008). This service is free of charge and online for 24 hour use.

The AUSPOS service was design with the following considerations (Dawson et al, 2001):

1. User friendly web page performance. 2. Dual frequency GPS data processor capability. 3. High quality standard in result. 4. Continuous and undisrupted service. 5. Easy and standard to upload the file. 6. Quick processing (less than approx. 15 minutes for each point). 7. The result will be returned by email to the user in PDF file format. 8. Could be used everywhere on the Earth. 9. GDA94 coordinate format for Australian users and ITRF for global users.

The computation of reference station coordinates for the Aceh project was performed using the AUSPOS online processor. GPS observation data must first be re-formatted into RE^EX format and then sent to the AUSPOS processor which is accessed via the Internet at www.ga.gov.au/bin/gps.pl. The processor requires the antenna height, type of antenna, a valid email address and dual frequency RINEX data. This processing used a 30 second sampling rate to accord with that of the three nearest IGS stations (short baseline) ; Bakosurtanal (BAKO) in Cibinong Indonesia, Cocos (Keeling) Island (COCO) in Australia and Bangalore (IISC) in India. AUSPOS automatically chooses these stations and recommends a minimum of 6 hours GPS data observation. GA claims that their online processing service could provide accuracy to less than 10 mm horizontal and less than 20 mm vertical (Dawson et al, 2001). The result from the AUSPOS service would be used as reference coordinates for the subsequent network RTK simulations. Chapter 7 NETWORK RTK SIMULATION

Fig. 7.1. Nearest IGS stations for reference points data processing.

lotion RMS (m) - Longitudd'^ RMS(m) Height RMS(m) Khaju 5° 36' 11.0474" 0,006 95° 22' 35.5528" 0,001 -33,198 0,006 GH 5° 33' 58.0874" 0,008 95° 20' 58.0793" 0,029 -30,734 0,004 Lhoknga 5° 29' 7.9268" 0,004 95° 15' 23.0194" 0,016 -23,636 0,013 Table 7.1. Reference points coordinate result.

The coordinates must be expressed in a geodetic system because SpiderNet requires this for reference coordinate input. Table 7.1 shows the coordinate result and its error of the reference points from AUSPOS processing. The rms value varied from below 10 mm for latitude, 1-30 mm for longitude and less than 15 mm for height.

Baseline processing using LGO has been conducted for checking the AUSPOS processing result as can be seen in table 7.2. Chapter 7 NETWORK RTK SIMULATION

Khaju 5° 36' 11.0490" 0.0016" 95° 22' 35.5360" 0.0168" -33,3515 0,1535 GH 5° 33' 58.0891" 0.0017" 95° 20' 58.0621" 0.0172" -30,1414 0,5926 Lhoknga ' 29' 7.9273" 0.0005" 95° 15' 23.0016" 0.0178" -23,7823 0,1463

Table 12. Reference points coordinate result from LGO processing.

The different in latitude from AUSPOS result and LGO result is 0.0005"-0.0017" and is a bit high in longitude from 0.0168"-0.0178". The highest different is in height from 0.1463-0.5926 m. Overall, there is no significant difference between AUSPOS and LGO result.

7.1.2. GPS Static Processing

Static processing for each rover point was computed to check the AUSPOS absolute results in a relative sense. This is crucial for the successful operation of network RTK processing. In this processing mode, the Leica Geo Office (LGO) software was used for processing 15 baselines using 1 reference station with AUSPOS derived coordinates. These 15 baselines were processed from five points in three sessions and constrained to one reference point. The first session was from 9-1 pm comprising five points observed with 10-20 minutes duration for each point. The second session was from 2-4 pm and the third from 4-6 pm.

The parameters applied for the static processing related to GPS data, satellite ephemeris and the default model for troposphere and ionosphere corrections from the software. The parameters that were used as listed below:

1. Cut off angle 15 degrees 2. Ephemeris Precise Ephemeris 3. Sampling rate 1 second 4. Troposphere correction Hopfield 5. Ionosphere correction lono free fixed solution Chapter 7 NETWORK RTK SIMULATION

The processing strategy adopted one reference station to each rover point as a single baseline and no network had been formed in baseline processing. Only one reference station was used for static processing as the network RTK processing only used the closest reference point for producing a network RTK RINEX file. This resulted in five baselines and five rover point coordinates. In total, there will be 15 baselines and 15 coordinate results at three different times.

7.1.3. Network RTK GPS Simulation

The simulation in network RTK used Leica SpiderNet software version 3.0. This version is able to set a path which can store real time products. This software is designed for real time applications, but also offers a re-process facility for research purposes such as network testing before hardware installation (Leica, 2005). All re-processing functions in SpiderNet function identically to the real time mode.

Basically, SpiderNet software has five key components: site server, network server, cluster server, RTK proxy server and the SpiderNet user interface (if it runs in real time) (Ibid, 2005). In this simulation, the key components were simplified because all simulations were run inside the network server. In addition, the LGO software was used for processing the RINEX data results from network RTK processing.

In general, the network RTK simulation followed the steps as listed below:

1. Switched SpiderNet real time processing mode into re-processing mode to avoid time stamp issues. 2. Set up three reference stations as simulated RINEX sites. Because all GPS receivers are Leica branded (System 500 and 1200), the GPS raw data (MDB file) could be directly loaded on network server. Chapter 7 NETWORK RTK SIMUIA TION

3. Configured a cluster including three reference sites as well as a cell using the same sites.

4. Select the master station based on the closest reference station with rover points.

5. Input the NMEA position based on approximate rover position. The SpiderNet version 3.0 was completed with Tool TestRTK that was used to get the streaming of "real time" simulation products. 6. Model the master auxiliary correction (MAC) and start to send and store the correction. 7. Static processing using RINEX "real time" products with rover data in LGO software.

95 M 4'24.00000" E 95 M 6'48.00000" E 95'19' 12.00000" E 95'21'36.0^00" E

5'36- 00.00000" N

e ®

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Fig. 12. Cluster and cell based on three reference stations.

Fig 7.2 represents the cluster and cell configuration from the three reference stations (green triangle) in SpiderNet software when the simulation ran. The GH reference, the closest to rover points, was used as a master station when the SpiderNet began streaming the network correction based on the triangle area of Chapter 7 NETWORK RTK SIMl/IA TION

the reference points. The result of the rover point positions is shown as a circle in the network.

The simulation covered the three different time epochs mentioned previously. Each time frame consisted of one master station and five rover observations. All rover points were close to the GH reference station, so there was only GH as a master station in this simulation. As mentioned above the MAC streaming data was generated by network computation and the coordinate approximation from each rover point. Therefore, every point generated unique MAC streaming data. Then, the coordinate and baseline were processed using LGO software. The processing in LGO involved the result from network RTK result (RINEX format) and the "real" GPS data from the rover points.

KNWL 592480,7046 6320418,3573 1246,2814 No NRTK KNWL 592480,5999 6320418,6654 1246,3083 Yes Static 0,1047 -0,3081 -0,0269

BTJ 590686,7060 6320672,7695 1178,2577 Yes NRTK BTJ 590686,6828 6320672,2944 1178,2283 Yes Static 0,0232 0,4751 0,0294

PP 588721,1170 6321004,0337 3404,9327 No NRTK PP 588720,6430 6321002,4620 3405,2150 Yes Static 0,4740 1,5717 -0,2823

PTK 588032,9211 6321131,9731 4328,3049 Yes NRTK PTK 588032,8199 6321130,5815 4328,2891 Yes Static 0,1012 1,3916 0,0158

PNY 588362,0453 6320972,9572 3564,2052 No NRTK PNY 588361,7071 6320970,9638 3564,3526 Yes Static 0,3382 1,9934 -0,1474

Table 7.3. Result of the first session comparing network RTK (NRTK) with static processing for five rover points from the GH base station.

Table 7.3 showed the result of the first session conducted from 9-12 am. This table contains the results from processing using the SpiderNet derived result and Chapter 7 NETWORK RTK SIMULATION

Static processing of the entire observation span using LGO software as a practical comparison. The static processing solved the ambiguity resolution successfully for each point. However for network RTK only 2 points (BTJ and PP) resolved the ambiguities successfully.

The baseline length from the GH reference station to each rover point varied from 1 km to almost 4.5 km. The result showed that the difference in baseline length between static and network RTK processing result was about 1.6 to 28 cm. The difference in easting was 2-47 cm and for the northing there was a big difference ranging between 30-200 cm.

2 KNWL 592480,8185 6320418,4144 1246,4072 No NRTK KNWL 592480,592 6320418,6819 1246,3045 Yes Static 0,2262 -0,2675 0,1027

BTJ 590687,2788 6320673,6841 1177,8094 No NRTK BTJ 590686,675 6320672,2789 1178,2354 Yes Static 0,6036 1,4052 -0,4260

PP 588720,7418 6321002,2962 3405,1900 No NRTK PP 588720,636 6321002,4755 3405,2247 Yes Static 0,1062 -0,1793 -0,0347

PTK 588032,8590 6321131,4257 4328,2946 Yes NRTK PTK 588032,8140 6321130,5496 4328,2918 Yes Static 0,0450 0,8761 0,0028

PNY NRTK PNY 588361,71 6320970,9653 3564,3500 Yes Static

Table 7.4. Result of the second session comparing network RTK (NRTK) with

static processing for five rover points from the GH base station.

The second observation that was conducted during between 1-4 pm is listed in table 7.4. All points in the static processing successfully re-solved the ambiguities.

However, only one point in the network RTK processing could re-solve the ambiguities. In this session, the MAC product stopped streaming network Chapter 7 NETWORK RTK SIMULATION

corrections entirely at the end of the session. Therefore there was no coordinate result for network RTK observations at the PNY point. The baseline difference between static and network RTK was around 0.2-40 cm. In addition, the difference in easting was between 4.5-60 cm and northing was around 26-140 cm.

3 KNWL 592480,5297 6320418,2553 1246,3147 Yes NRTK KNWL 592480,6046 6320418,6768 1246,3040 Yes Static -0,0749 -0,4215 0,0107

BTJ 590685,8654 6320672,3573 1179,0771 No NRTK BTJ 590686,6856 6320672,2871 1178,2258 Yes Static -0,8202 0,0702 0,8513

PP NRTK PP 588720,4954 6321002,2852 3405,3641 Yes Static

PTK NRTK PTK 588032,8306 6321130,6046 4328,2845 Yes Static

PNY 588361,6987 6320971,1421 3564,4079 No NRTK PNY 588361,6999 6320970,9244 3564,3557 Yes Static -0,0012 0,2177 0,0522

Table. 7.5. Result of the third session comparing network RTK (NRTK) with static processing for five rover points from the GH base station.

Table 7.5 shows the third session result. During the third session, conducted between 4-7 pm, the MAC streaming dropped out in the middle of session so that network RTK processing for the PP and PTK rover points could not produce coordinates or baselines. All points in static processing were successful for ambiguity resolution but there were only two points in the network RTK processing that successfully resolved. In the baseline result, the difference ranged from 1-85 cm. The easting difference was between 0.1-82 cm and the northing difference was 7- 42 cm. Chapter 7 NETWORK RTK SIMULATION

7.1.4. Baseline Result of Epoch by Epoch Processing

Because of the large difference in the results between static processing and NRTK processing, it was necessary to look through the epoch by epoch (for about 600- 1000 seconds) result session per session with static approach in every baseline and point. Fig 7.3, 7.4 and 7.5 are the results of epoch by epoch processing for GH- KNWL baseline. The complete figures of the processing result are presented in Appendix A.

1247.0

1246.5 -

1246.0

£ 1245.5 Q) •NRTK .E 1245.0 0) • Static (S 1244.5 OQ

1244.0

1243.5

1243.0 200 400 600 800 Epoch

Fig. 7.3. Baseline GH-KNWL, first session. Chapter 7 NETWORK RTK SIMULATION

1248.0

1247.5

E ^0 1247.0 V J C •NRTK o •Static («0 1246.5 QQ

1246.0

1245.5 200 400 600 800 1000 Epoch

Fig. 7.4. Baseline GH-KNWL, second session.

1247.0

0) •NRTK .E 1246.5 0) • Static w (0 m . /

1246.0 —r r— ^ 1 200 400 600 800 1000 Epoch

Fig. 7.5. Baseline GH-KNWL, third session

The network RTK baseline result fluctuated in every session. The baseline difference with the static result in the first session is around 35-300 cm. In addition, the baseline error of the network RTK result is around 1-150 cm. On the other hand, the baseline error from static processing was quite stable in all sessions. It was below 5 cm. In the second session, the difference between Chapter 7 NETWORK RTK SIMULAT/ON

baselines reduced to around 50-160 cm which is still unacceptably high. In this session, the GH-PNY gave no result due to the failure of streaming of network RTK corrections. The baseline error difference in this session was around 5-90 cm. In the third session, there were no results from the two baselines (GH-PP and GH-PTK) processing due to the failure of streaming of network RTK corrections. The baseline difference in the third session was around 32-220 cm and the baseline error was around 20-245 cm.

7.1.5. Point Result of Epoch by Epoch Processing

Epoch by epoch processing was used to identify fluctuations of the coordinate result in every epoch. It is then compared with the static processing result. Fig 7.6, 7.7, 7.8, 7.9, 7.10 and 7.11 are the result of epoch by epoch processing in point KNWL. The complete figures of the processing results are presented in Appendix A.

592481.0 1

592480.5 -

O) c •NRTK ••g 592480.0 - (0 •Static Ul

592479.5 -

592479.0 - 1— 1 ^ 1 0 100 200 300 400 500 600 700 Epoch

Fig. 7.6 Easting on KNWL, first session Chapter 7 NETWORK RTK SIMULA TION

6320427

6320424 -

O) 6320421 £ •NRTK t •Static ZO 6320418 J

6320415 ^

6320412 0 100 200 300 400 500 600 700 Epoch

Fig. 7.7. Northing on KNWL, first session

592482.0

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O) 592481.0 •NRTK toM 4 •Static "J 592480.5 iv/^ -M r""^*""'"''^''^ 592480.0

592479.5 —^ ^ 200 400 600 800 1000 Epoch

Fig. 7.8 Easting on KNWL, second session. Chapter 7 NETWORK RTK SIMULA TION

6320421

6320418

O) c — "»r—— 6320415 •NRTK O •Static z fvJ

6320412 Xj ^

6320409 200 400 600 800 1000 Epoch

Fig. 7.9. Northing on KNWL, second session.

592481.5

592481.0 O) c •NRTK (0 (0 •Static LU 592480.5

592480.0 0 200 400 600 800 1000 Epoch

Fig. 7.10. Easting on KNWL, third session. Chapter 7 NETWORK RTK SIMULATION

6320418

O) c 'JE •NRTK •c o •Static z

6320415 100 200 300 400 500 600 700 800 900 Epoch

Fig. 7.11. Northing on KNWL, third session.

The first session displayed approximately 12-210 cm in easting differences for all of the points as compared with the static result. In addition, the northing difference was around 70-125 cm. In the second session, the easting difference between the network RTK result and the static result was around 40-300 m and then decreased to around 70-100 cm in the following session. In the second session, the northing difference was higher than the first session. It was around 330-600 cm and then the value remained stable in the final session. All of these results (baselines and points) are unreasonably high and point to a problem with either the geometry of the network, the SpiderNet network RTK re-process mode or the number of satellites used in the solutions. Further discussion about the problem will be addressed in the following section.

7.1.6. Common Satellite Requirement

The requirement for a minimum of five common satellites is crucial during the network correction processing and MAC streaming (Leica, 2005). In this Chapter 7 NETWORK RTK SIMULATION

simulation, the average time with common satellites was quite good in the first session with 6-7 satellites visible at all times. In contrast, in the second and third session there were only 4-6 common satellites. This means that during the period with a lack of satellites, the SpiderNet was not able to generate a network correction and send it in MAC mode. This has occurred despite the survey planning that showed (see chapter 6 section 6.4) that at all times 9-10 satellites are visible. In fact, the actual data does not have enough satellite (5) to produce network correction (see table 7.7 and 7.8).

1 GH - KNWL 10' 2.5.6.7.9.12.18 7 - GH - BTJ 20' 2.5.6.7.9.12.18 7 - GH-PP 12' 5.6.7.9.12.18 6 SV12set GH - PTK 12' 5.6.7.9.14.18 6 - GH - PNY 15' 5.6.7.9.14.18 6 -

Table 7.6. Common satellites in the first session.

The length of observation for a rover point in the first session was around 10 to 20 minutes. Table 7.6 showed that there were a minimum suitable number of satellites for SpiderNet to produce network corrections and generate MAC streaming.

2 GH - KNWL 15' 1.5.7.12.14.18 6 SV 7 set GH - BTJ 15' 1.5.12.14.18 5 - GH-PP 13' 1.5.14.18 4 SV 5 set GH - PTK 10' 1.5.14.16.18 5 - GH - PNY 14' 1.14.16.18 4 -

Table 7.7. Common satellites in the second session.

In table 7.7, the second session observation of rover points is shown. It shows there was a time when SpiderNet could not produce the network corrections based Chapter 7 NETWORK RTK SIMULATION

on a low number of satellites for network processing. Two satellites were also disappeared below the horizon during the observation.

3 GH-KNWL 10' 1.14.16.18 4 SV 1 set GH - BTJ 10' 1.14.16.18 4 - GH-PP 10' 1.3.14.16 4 SV14set GH - PTK 10' 1.3.14.16.20 5 - GH - PNY 15' 1.3.14.16 4 -

Table 7.8. Common satellites in the third session.

The third session was the worst for common satellite availability. For 10-15 minutes observations for the rover points, there was only one observation that could fulfill the five common satellite requirements. As can be seen in table 7.5, there was a point that could not compute its coordinate as the SpiderNet failed to produce network corrections.

7.1.7. Network Strength

There is no specific limitation for the number of reference receivers used when generating network corrections. However, five or six reference stations will give a better result for the network corrections than the three used in Aceh due to the strengthening of the network geometry and better modeling of large scale atmospheric effects (Leica, 2005). In addition, in real time applications, it will help the rover receiver not to lose its fix if the communication link drops out. If the network only consists of three reference stations, the network correction will not be produced if one of the reference stations drops its communication link

(Ibid, 2005).

The problem in this simulation was mainly due to unfavorable network geometry from the three reference stations chosen under difficult circumstances. The triangle network was long and thin rather than equilateral. It led to bad network Chapter 7 NETWORK RTK SIMULATION

fixing behaviour for the three reference sites in the network processing and a significant amount of time where less than five satellites were available for the network solution. In addition, there was no significant improvement for network solutions because of the distance between reference stations was less than 20 km.

It was clear from this testing that the data gathered in Aceh was not suitable to use to compare the network RTK method with single base RTK and static baseline processing. An alternative data set was therefore sourced from the Singapore Satellite Positioning Reference Network (SiReNT). Results from this processing are shown in the next section.

7.2. Network RTK Simulation Using SiReNT

As the data from Aceh was unsuitable for the re-processing operation proposed, data from a well established network in Singapore was used to test the thesis that Network RTK is more reliable than single base RTK in equatorial regions-even for relatively short baselines.

As with the Temporary CORS network project, the re-processing simulation consisted of collecting GPS data from reference stations, processing the data in the network RTK post processing mode to produce RINEX data and then processing the rover data using the network RTK RINEX product. The location in Singapore was quite close to Banda Aceh and still in the equatorial region. The purpose of this comparison is to compare the performance of the Singapore data against the Aceh data to establish if the poor Aceh results were due to the poor network geometry, low number of common satellites, the length of data captured or if it was a software problem with SpiderNet. Chapter 7 NETWORK RTK SIMULATION

7.2.1 Singapore Satellite Positioning Reference Network (SiReNT)

This infrastructure used was the Singapore Satelhte Positioning Reference Network (SiReNT) (formerly Singapore Integrated Multiple Reference Station Network (SIMRSN)), which is one of the first and most established network RTK GPS infrastructures in Asia. This network is operated and deployed by the Singapore Land Authority (SLA). SiReNT is mainly operated for supporting cadastral survey information in the Republic of Singapore, some spatial applications and surveying works (Peng, 2007). The network consists of five reference stations distributed in Loyang marked as SLOY, Keppel Club marked as SKEP, Nanyang Technological University marked as SNTU, Senoko marked as SSEK and Nanyang Polytechnic marked as SNYP (see fig 7.12).

The distance from each station varies from 10-20 km. Each station is using a Trimble GPS geodetic dual frequency receiver with choke ring antenna. The network RTK computation uses the Virtual Reference Station (VRS) concept that has been tested in Nanyang Technological University (Hu et al, 2003). This concept was relatively simple to apply in network RTK GPS. The network correction was made based on the navigation position sent from the rover receiver (red rectangle, see Fig. 7.12). Then, the precise rover position was generated from the nearest reference station (Ibid, 2003). SSEK^ Senoko' V'o ^

TechnologicaNanryang"'..l^ - ^ D .*' o

- ^ Club ^S^Sentosa

r;Si .. SoutSoutherislandh sn

Fig 7.12. SiReNT reference stations (SiReNT, 2007). Chapter 7 NETWORK RTK SIMULATION

7.2.2. Simulation Method

The simulation method did not include reference stations processing because the reference stations already have known coordinates in the WGS84 system. The reference point coordinates are crucial for simulation input in SpiderNet software.

SSEK 1° 28' 13.35539" N 103° 48' 52.24951" E 40,715 SNYP r 22' 44.89777" N 103° 50' 55.49480" E 55,490 SLOY r 22'21.49347" N 103° 58' 17.96433" E 50,957 SKEP 1° 16' 01.83442" N 103° 48' 25.93532" E 37,481 SNTU 1° 20' 44.92909" N 103° 40' 47.77635" E 76,162

Table 7.9. Reference station coordinates.

Running the re-processing simulation was identical to the Aceh data. The first requirement was that all the data for simulation must be converted into RINEX format and the epoch of observations was 1 second. The simulation would act as MAC SpiderNet processing whereby the basic principle is quite similar with the VRS method (see chapter 4 section 4.5.1).

7.2.3. Network Correction Processing

The simulation began with creating a cluster and cell to produce network corrections by uploading all reference station data in the SpiderNet software. There were five reference stations (see fig 7.12) that had been used for producing network correction data. This simulation also used two rover stations that had two different time epoch observations.

Generally, the network correction would process the network that had been formed from five reference stations. There were four triangles as a cell in a large cluster The two rover points were located in the cell SKEP-SNYP-SLOY. The network RTK RINEX file would be generated from the closest reference station to Chapter 7 NETWORK RTK SIMULA TION

the rover. Rover point 15399 would use SKEP as a reference station and rover point 1648 would use SLOY.

1 16480 1533036,7016 6189442,0897 8960,9557 No NRTK 16480 1533037,1531 6189442,0122 8960,8804 Yes Static -0,4515 0,0775 0,0753

15399 1525094,5071 6191415,9431 6202,9043 Yes NRTK 15399 1525094,6935 6191415,7710 6202,9025 Yes Static -0,1864 0,1721 0,0018

2 16480 1533036,8108 6189442,0386 8960,8857 Yes NRTK 16480 1533037,1486 6189442,0104 8960,8831 Yes Static -0,3378 0,0282 0,0026

15399 1525094,4795 6191415,9588 6202,9043 Yes NRTK 15399 1525094,6742 6191415,7853 6202,8880 Yes Static -0,1947 0,1735 0,0163

Table 7.10. Result of first and second session.

Table 7.10 showed the result of the re-processing simulation. As a comparison to the method used with the Temporary CORS simulation using the Aceh data, static processing results were also computed. The static processing was able to solve ambiguity resolution in all points. But in network RTK, there was a point that failed to resolve the ambiguities. In the first session the difference between baselines was around 0.1-7 cm and the second session was around 0.2-1.6 cm.

For the easting difference, there was around 18-45 cm in the first session and 19- 33 cm difference in the following session. In addition, the northing difference showed nearly similar result in all sessions between 2-17 cm. This result was quite unsatisfactory. The possibility of this bad result was from ionospheric refraction in the equatorial region corrupting initialisation. In the following section, there will be a comparative test using LI and L1+L2 for identifying possible

ionospheric effects. Chapter 7 NETWORK RTK SIMULATION

7.2.4. Baseline Result of Epoch by Epoch Processing

Fig 7.13 and 7.14 are the results from epoch by epoch processing in baseline SKEP- 15399. The complete result of network RTK baseline processing epoch by epoch can be seen in Appendix B. As a comparison, the figures also include the static processing results.

6202.95

6202.90

•NRTK 0) •Static (w0 6202.80 OQ

6202.75

6202.70 100 200 300 400 Epoch

Fig. 7.13. Baseline SKEP-15399, first session. Chapter 7 NETWORK RTK SIMULA TION

6202.95

6202.90

6202.65 100 200 300 400 Epoch

Fig. 7.14. Baseline SKEP-15399, second session.

In the first observation session of point 15399, the epoch by epoch error for baseline SKEP-15399 processing was between 5-20 cm. The pattern of network RTK and static baseline and its error were similar (see in Appendix B). However, in particular epochs there was still noise in the network RTK result that influenced the baseline error. The result of the second session in baseline SKEP-15399 was similar with the first session. Some noise still rose up in one particular epoch time of the network RTK processing. The baseline error for network RTK processing was around 1-12 cm.

The baseline error of the network RTK result in baseline SLOY-16488 fluctuated a lot and reached a highest value of almost 400 cm. But since epoch 100, there was a good indication that the error was similar with the static result. In the second session, the baseline error fluctuated early in the observations and again near the end. The range of error was around 1-50 cm. Chapter 7 NETWORK RTK SIMULATION

7.2.5. Point Result of Epoch by Epoch Processing

Fig 7.15, 7.16, 7.17, 7.18 are the result from epoch by epoch processing in point 15399. The complete results of points epoch by epoch can be seen in Appendix B. A static processing result was also included as a comparison.

1525095

O) 'iS •NRTK 0) • Static lU(0

1525094 100 200 300 400 Epoch

Fig. 7.15. Easting on 15399, first session. Chapter 7 NETWORK RTK SIMULATION

6191417

6191416 - O) c !E •NRTK t o •Static

6191415

6191414 0 100 200 300 400 Epoch

Fig. 7.16. Northing on 15399, first session.

1525095

O) c •Netwok RTK (tn0 •Static LU IsT

1525094 100 200 300 400 Epoch

Fig. 7.17. Easting on 15399, second session. Chapter 7 NETWORK RTK SIMULATION

6191416

O) c !E •NRTK t 6191415 o •Static z

6191414 100 200 300 400 Epoch

Fig. 7.18. Northing on 15399, second session.

For point 15399 during the first session of processing, the result between network RTK and static processing was quite similar. But for network RTK processing, there was noise around epoch 110 to 170 that made the coordinate difference quite large. Meanwhile, in the second session, the pattern of coordinate difference was similar. Like the first session, there was still noise that influenced coordinate processing. In particular, the noise occurred around epoch 150 to 200.

The difference between the network RTK and static processing in the first session of point 1648 fluctuated at the beginning. But since epoch 100, the coordinate diagram showed a similar pattern with the static result. The noisy result occurred again in the second session of point 1648. The result fluctuated in the beginning and again at the end of the observation period. Chapter 7 NETWORK RTK SIMULATION

7.2.6. Common Satellite Requirement

Session Baseline length of Observation Common Sateiiitew Note 1 SKEP - 15399 15' 2.5.6.7.9.12.14.18.21 9 _

SKEP - 15399 15' 5.6.7.9.12.14.18.21 8 -

2 SLOY-1648 15' 2.4.5.10.12 5 SLOY-1648 15' 2.4.5.6.9.10.12 7 -

Table 7.11. Common satellites in the first and second session.

Table 7.11 shows the common satellites during network RTK processing at the SLA site. For baseline SKEP-15399 there was a suitable number of satellites to produce the correction. The number of common satellites was usually 8-9. However for the SLOY-1648 baseline there was a minimum requirement (5 satellites) available. It correlated with the epoch by epoch processing result for the baseline and 1648 coordinate where some error and noise occurred.

7.2.7. LI Processing Test

The ionospheric effect can be clearly seen in single frequency baselines as compared to dual frequency baselines (Camargo et al, 2000). Theoretically, the use of dual frequency GPS receivers will eliminate the ionospheric effect (Ibid, 2000). SLA reference stations use dual frequency GPS receivers. For checking the effect of ionosphere, LI processing from SLA network was carried out. The check was done at point 15399 where it was suspected that the ionospheric effect influenced the baseline result. Chapter 7 NETWORK RTK SIMULATION

6203.1

6203.0

— 6202.9 •L1+L2 NRTK •LI NRTK L1+L2 Static LI Static

6202.5 50 100 150 200 250 300 350 Epoch

Fig. 7.19. Baseline comparison from LI and L1+L2 processing in point 15399 first session.

•L1+L2 NRTK •L1 NRTK UJ 0) L1+L2 Static c © L1 Static v> mK

50 100 150 200 250 300 350 Epoch

Fig. 7.20. Baseline error from LI and L1+L2 processing in point 15399 first session.

Fig 7.19 shows the comparison of baseline result from LI and L1+L2 processing in static and network RTK mode. There is a bit strange result from L1+L2 static and L1+L2 network RTK. From the first epoch till epoch 112, the pattern is quite Chapter 7 NETWORK RTK SIMULATION

similar. But, since epoch 113-170 there is a jump which affected the network RTK but not the static. Then, it tracks back nicely in epoch 171-314. It happened almost similar in baseline error diagram (see fig 7.20). This phenomenon will be more supported by cross correlation test in the next section.

The difference between LI and L1+L2 baselines was almost 70 cm. In addition, the baseline error fluctuated radically from 5 to almost 90 cm (see fig 7.20). This is typical of ionospheric effects on single frequency GPS baseline results. Fig 7.19 and 7.20 showed that the baseline processing suffered from ionospheric effects.

7.2.8. Cross Correlation

The cross correlation is a statistical test that has a purpose for cross check the relationship of two different variables. Harvey (2006) gave an equation for computing the correlation between two sets of data observation:

nLx.y^ -^i'^yi P.. = (40)

Where:

A, correlation between two sets data first data set

second data set

n total number of data

The correlation value varies from -1 to 1. If the correlation is close to -1 or 1, it means that the two variable data sets compared have a lot in common. If the value is positive, it indicates that one variable's increase is associated with the increase of the other variable. On the other hand, negative correlation means that one Chapter 7 NETWORK RTK SIMULATION

variable's increase is associated with the decrease of the other variable (Ibid, 2006).

Numeric test as a support for visualization in section 7.2.7 has been conducted by using cross correlation in two different data sets from LI vs. L1+L2 NRTK,

L1+L2 static vs. L1+L2 NRTK, LI vs. L1+L2 static and LI static vs. LI NRTK baseline result.

mm. ^ 4 DataSeto Cross Oorrelation 1 L1 vs. L1+L2 NRTK 0.2822 2 L1+L2 Static vs. L1+L2 NRTK 0.2665 3 L1 vs. L1+L2 Static 0.5171 4 L1 Static vs. L1 NRTK 0.7859

Table 7.12. Cross correlation in baseline SKEP-15399.

Table 7.12 presents the possible correlation in the SLA data simulation. The first correlation is comparing data LI vs. L1+L2 NRTK baseline result. The correlation value was about 0.2822, which means that there was little data in common. Visual inspection of fig 7.22 supports this result as can be seen LI (pink line) has a different pattern with L1+L2 (blue line) in the NRTK baseline result.

The noise in LI data is quite high and it is suspected that the LI data suffered from ionospheric effects.

The similar correlation (0.2665) is presented when L1+L2 static was compared with L1+L2 NRTK baseline result. It seems a bit strange result because only data from epoch 113-170 that jumped. Further test has been conducted to check if the datasets from first epoch to epoch 112 and data from epoch 171-314 are well correlated. The both test give the results that in that particular epoch the datasets are well correlated (0.9464 and 0.9612). It concludes that the jumping result in that particular epoch (113-170) influenced the cross correlation result as well as in baseline processing.

m Chapter 7 NETWORK RTK SIMULATION

Static processing results with LI and L1+L2 were also compared and the cross correlation reach 0.5171. A lot of common data can be seen when comparing this result from LI static and LI NRTK baseline processing. It was 0.7859 correlation value. It indicates that LI static and LI NRTK had the same pattern in noise.

The ionospheric problem at the equator will affect the density of a CORS network in this area. Ideally, for avoiding the ionospheric effect, the reference stations is not advised to place further than 20 kms apart in equatorial regions even for network RTK. Using RTK GPS is still reliable in equatorial region. But it has to be considered with the time of survey and inter-receiver distance as the traditional single based RTK uses dual frequency to initialize fast, but after that it effectively uses LI solutions. In this simulation, which is network RTK was not processed in real time, L1+L2 used iono free fixed solutions. Network RTK offers the opportunity to continue real-time operations even in the presence of ionospheric disturbances, but it still does not work reliably due to other software factors.

Operational surveyors should adhere to a best practice guideline to ensure that their work can be checked in the field to ensure accuracy. At present there is no international standard for best practice guidelines for RTK or network RTK surveying. Different institutions have drafted different guidelines depending on their local circumstances and legislation. It is a recommendation of this thesis that in the presence of potentially disturbing influences for real-time surveying operations, operational surveyors working in Indonesia should be guided by a new set of best practice guidelines to ensure the accuracy of land parcel definition. Chapter 7 NETWORK RTK SIMULATION Chapter 8 CONCLUSION AND RECOMMENDATION

Chapter 8 CONCLUSION AND RECOMMENDATION

8.1. Conclusion

Using GPS is inevitable in the development of modern surveying including cadastral surveying. The emerging development of continuously operating reference station (CORS) networks as an infrastructure to support GPS operations will reduce the number of classical ground based geodetic control points necessary to support land administration. Such an infrastructure can be upgraded into a network RTK capable system that is able to deliver centimetre level accuracy in a quick, robust and reliable manner. However, when using GPS for cadastral surveying, there are a few restrictions and requirements that need to be fulfilled to be acceptable as a part of a legal process. In Indonesia, GPS has been used for some cadastral processes particularly for definition of cadastral bench marks, however there are no cadastral regulations that specifically direct the use of GPS in this process.

The devastation of Aceh after the Boxing Day earthquake and tsunami presented special circumstances for land reconstruction. RTK GPS was used for establishing new cadastral benchmarks and re-coordinating land parcels in the land reconstruction project. However, there was still an obstacle for RTK GPS when extending the distance between the user and the nearest base station. Atmospheric conditions surrounding the equatorial region are more of a consideration for long distance single based RTK. Theoretically, network RTK can deal with this situation in a more robust manner. Network RTK can maintain similar accuracy as single based RTK even when extending the distance more than 20 km. The concept of network RTK GPS would be very useful if it is applied for land reconstruction due to the massive and large areas suffering destruction. In Chapter 8 CONCLUSION AND RECOMMENDATION

addition, this infrastructure will help converge cadastral and geodetic networks: a problem that has arisen in Indonesia over the last few decades.

Fieldwork for establishing a "simulated" network RTK test bed was conducted in the worst affected areas around Banda Aceh. This fieldwork did not seek to set up permanent sites, rather stable points as temporary sites. The early hypothesis of conducting a temporary CORS network project was that the network RTK GPS would give a more reliable solution and better result than single based RTK GPS. If this hypothesis could be proved by establishing a temporary CORS network approach, then this would be very useful for land reconstruction in regions like Aceh for Indonesian authorities. Rather than tackle challenging communications issues anticipated in Aceh, the project just logged static data at some reference stations and some rover points. This data was re-processed to simulate to a network RTK methodology. However the geometry of the network, lack of common satellites at the rover and reference station and noise of the observations precluded usable network RTK results to confirm the original thesis.

The noise and error sources could be identified as listed below:

1. Network strength. The network was a long, thin triangle with a poor geometry. As a result, this bad geometry precluded useful network RTK correction results. 2. Satellite availability. Survey planning before the fieldwork was carried out. The result of the survey planning showed that during the observation, there would be more than five common satellites (sometimes 10) that could be viewed simultaneously at all sites. In fact, sometimes network RTK processing failed to stream the corrections because there was a lack of common satellites that could be viewed. This case could be seen in the result of session 2 and 3. 3. Short distance between reference stations. Theoretically, network RTK will maintain centimetre level accuracy even if the distance between Chapter 8 CONCLUSION AND RECOMMENDA TION

reference stations is more than 20 km. On this project, the ionospheric effect was the main consideration for short baseUnes due to the anticipated high ionospheric effects near the equator. 4. Most rover points were outside of the network. From five rover points, only two rover points were inside the network. This allowed comparison of the results of points inside and outside the network.

As a comparison, a similar re-processing simulation was conducted. The simulation used well established network RTK GPS infrastructure from the Singapore Land Authority (SLA). The method of simulation was similar and some weaknesses in the previous simulation had been overcome as listed below:

1. Good geometry. The geometry of the network was quite good because it contained five reference stations across the area and formed a good triangle. 2. Satellite availability was good because all reference stations are mounted on the top of buildings with minimum obstructions or multipath. 3. The appropriate distance was applied. The distance between reference stations was about 15-20 km which was theoretically the suitable distance to compare network RTK with single base RTK. 4. All rover points were inside the network.

The result using SLA data was better given the length of baselines. Static computation has been done to see the different result between network RTK and static processing. The difference results in baseline length between network RTK processing and static processing was 0.1-7 mm. The difference between network RTK results and static processing in easting was around 18-45 mm and the northing was around 2-17 mm. But still there was an error and noise occurred during network RTK processing. Chapter 8 CONCLUSION AND RECOMMENDA TION

From the Aceh data, there was a period of time the network RTK GPS failed to produce a good result and network correction streaming. It mainly suffered from bad network geometry of the reference station network and the lack of common satellite observations. In the cases where this problem was overcome, there were still unsatisfactory results in network RTK processing. Aponte et al (2008) in their study about network RTK assessment stated that network RTK mainly suffered from a low number of satellites in view, the constellation geometry, high ionospheric activity and completeness of the correction. Lack of satellites is the main reason that network RTK failed to produce a correction in session two and three for the Aceh data.

It is still unclear why with up to 10 available satellites that the network RTK solution only used five or less satellites therefore disallowing a solution. Consultations with technical personnel from Leica also did not resolve the issue. The reference station coordinates were checked and correct. The ionosphere was not particularly noisy. The geometry of the network was poor and perhaps this was the major contributing reason, however with only user access to the software it remains a mystery as to why the number of available satellites was limited. This outcome is certainly a warning to users of network RTK products in equatorial regions and an impetus for further research to resolve this issue.

In addition, the LI test that was conducted using the SLA data showed that network RTK is affected by ionospheric activity in the equatorial region such that cm-level positioning is not possible for some periods. For cadastral applications, this is not acceptable and reinforces the need for user guidelines for legal surveys using GPS techniques in equatorial regions so that periods of low accuracy can be avoided or poor results can be identified.

Indonesia has established geodetic and cadastral infrastructure using GPS in the past. The development of GPS technology must be embraced by the Indonesian Chapter 8 CONCLUSION AND RECOMMENDATION

authorities for cadastral surveying activities due to its liigh productivity and ease of use. Regulations are quite important for providing legal currency and guarantee to GPS derived positions. New regulations for using GPS in cadastral surveying must be established quickly because some cadastral works have already been completed using GPS as a surveying instrument. The use of GPS and the development of CORS networks should be a solution for Indonesia and herald a new era of establishing and unifying the geodetic and cadastral frameworks across the country.

9.2. Recommendation

The temporary CORS network simulation had been done in post processing mode. It will be considerably more challenging (although theoretically and technically achievable) if this concept could be realized in real time using some communication equipment and more permanent sites. The interesting aspect of this concept is the low cost nature of a recyclable network RTK GPS infrastructure and its usability in areas with limited infrastructure. This concept still needs more research into using "over the air" communications and using scientific software for reference station coordinate processing. Another factor that can support "over the air" communication is that the trend in communication infrastructure is moving toward widespread wireless broadband access such as WiMAX. Many municipalities are developing this wireless access that can cover a wide area. Therefore, most areas, in particular in the city, could be more accessible using this internet service.

GPS researchers have investigated ionosphere effects, however little work has been done in equatorial regions. This area has the most active ionosphere due to the location and higher activity of the magnetosphere. Some researchers have successfully developed algorithms for ionospheric correction and these are applied in static GPS processing software. Traditional single-based RTK ignores the ionospheric effects and essentially produces LI only results after initialisation. Chapter 8 CONCLUSION AND RECOMMENDA TION

This is the major hmiting factor when using single based RTK-especially in equatorial regions. On the other hand, in this research, L1+L2 were post processed using iono-free fixed solutions as a benchmark for comparison. Network RTK seeks to overcome ionospheric effects in real-time, even for longer baselines, however this research has showed that results are still unreliable due to a number of factors as well as ionospheric disturbance. This leads to the conclusion that a 20 km distance between a base and rover remains a challenging goal in equatorial regions.

A major problem in network RTK is the availability of common satellites at each reference station which are used in the network RTK solutions. Further research should pursue how to maximize the number of satellites used in a network RTK processor and what factors affect the use or rejection of satellites. Issues such as cut off angle, data noise, skyview, rising and setting satellites and multipath may all contribute to a network RTK processor rejecting a satellite from a solution.

GPS can be a reliable technique to be used for cadastral activities surrounding equatorial areas, however the time of day for GPS operations should be chosen carefully. The lONEX diagram as shown in chapter 5, presented the characteristic of the ionosphere at the equator which peaked at midday. Rosario & Santos (2008) compared network RTK results during the day and the night in Puerto Rico. The results showed that the day result degraded almost 50% in accuracy compared to the night result due to tropospheric and ionospheric disturbance (Rosario & Santos, 2008). The coming solar maximum is likely to cause major

problems.

Establishing a permanent CORS network across Indonesia will require many logistical problems to be overcome, however it would create an important infrastructure for land administration, scientific research and datum unification as well as supporting national surveying and mapping operations. Such a goal could be achieved with collaboration between institutions that use geospatial data Chapter 8 CONCLUSION AND RECOMMENDATION

(Bakosurtanal, BPN, PBB and LIPI). A joint project would be the most suitable in establishing this infrastructure.

Moreover, the best practice guidelines of operational use for GPS must be established as well as regulations for GPS in cadastral surveying. Generally, the guidelines should include the GPS instrument validation, general requirements, limitation in using GPS, datum issues, surveying techniques and the accuracy expressed with respect to a well understood measure by surveyors such as class and order or more modem terms such as positional and local uncertainty. There are no specific best practice guidelines for RTK GPS in cadastral surveying at the moment. Different institutions use different guidelines depending on their local interest and circumstances. It is highly recommended that Indonesian cadastral and surveying authorities should create the best practice guidelines to ensure the accuracy of land parcel definition. REFERENCES

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Wubbena, G., Bagge, A. (2002). RTCM Type 59-FKPfor Transmission ofFKP version IM, Geo++ White Paper Number 2002.01. Xue, Z. R., Boon, K. T. (2004). The Variation offoFl in the Equatorial Ionosphere. IEEE online journal. Viewed 19 February 2008. Zhang, K., Talbot, N., Hale, M., Millner, J., (2001) Victorian High Precision Permanent GPS Tracking Network System, 14^^ International Technical Meeting of Satellite Division of The US Institute of Navigation, Salt Lake City, Utah 11-14 September 2001. APPENDIX

APPENDIX A

I. Network RTK Simulation Result from Aceh I.l. Baseline Result of Epoch by Epoch Processing

1180.0 1179.5 -

^^^ 1179.0 - 1178.5 - E i»* • 1178.0 - o •NRTK c 1177.5 - "o) •Static (0 1177.0 - <0 m 1176.5 - 1176.0 - 1175.5 1175.0 - 200 400 600 800 1000 1200 1400

Epoch

Baseline GH-BTJ, first session.

Baseline Error GH-BTJ, first session. APPENDIX

1178.5

£ 1178.0 a> •NRTK (D •Static (0 (S 1177.5

1177.0 0 100 200 300 400 500 600 700 800 Epoch

Baseline GH-BTJ, second session.

Baseline error GH-BTJ, second session. APPENDIX

1181.0 1180.5 'g 1180.0

1178.5 -^(^-yr—

1178.0 200 400 600 . 800 Epoch

Baseline GH-BTJ, third session.

Baseline error GH-BTJ, third session. APPENDIX

1247.0

1246.5

1246.0 -

1245.5 -

1245.0 •NRTK 0) •Static (0 1244.5 - m 1244.0

1243.5

1243.0 0 200 400 600 800 Epoch

Baseline GH-KNWL, first session.

Baseline error GH-KNWL, first session. APPENDIX

1248.0

1247.5 -

0) 1247.0 c •NRTK

1246.0 -

1245.5 200 400 600 800 1000 Epoch

Baseline GH-KNWL, second session.

Baseline error GH-KNWL, second session. APPENDIX

Baseline GH-KNWL, third session.

Baseline error GH-KNWL, third session. APPENDIX

3565.0

3564.5 -

0) .E 3564.0 •NRTK a> •Static (0 m 3563.5

3563.0 0 200 400 600 800 1000 1200 Epoch

Baseline GH-PNY, first session.

Baseline error GH-PNY, first session. APPENDIX

3565.5

3565.0 -

0) 3564.5 •NRTK 0) 0) •Static (D m 3564.0

3563.5

200 400 600 800 Epoch

Baseline GH-PNY, third session.

Baseline error GH-PNY, third session. APPENDIX

3410

3405 J

3400

^ 3395 ^ 0) .E 3390^ •NRTK 0) •Static g 3385 m 3380

3375 ^

3370 0 200 400 600 800 1000 1200 1400 Epoch

Baseline GH-PP, first session.

2.0 1 ru )L2_ 1.0 liJ •NRTK 0) Static B 0.5-i 0) D(O0 0.0

-0.5 200 400 600 800 1000 1200 1400 Epoch

Baseline error GH-PP, first session. APPENDIX

3405.5 1

0)

0) 3405.0 •NRTK (0 -fWI (0 •Static m

3404.5 r———1 1 1 ^ ; 0 100 200 300 400 500 600 700 800 900 Epoch

Baseline GH-PP, second session.

1.0

)>o_ •NRTK lU 0.5 - 0) •Static 0) (0 C(Q0 Jr~

0.0 0 100 200 300 400 500 600 700 800 900 Epoch

Baseline error GH-PP, second session. APPENDIX

4328.5

IT (D S 4328.0 •NRTK •Static Uio m(0

4327.5 200 400 600 800 1000 1200 Epoch

Baseline GH-PTK, first session.

Baseline error GH-PTK, first session. APPENDIX

4328.5

0) .£ 4328.0 •NRTK 0) 0) •Static (0 m

4327.5 -4 1 1 1 0 100 200 300 400 500 600 700 800 900 Epoch

Baseline GH-PTK, second session.

Baseline error GH-PTK, second session APPENDIX

1.2. Point Result of Epoch by Epoch Processing

O) c LU

0 200 400 600 800 1000 1200 1400 Epoch

Easting on BTJ, first session.

6320673

6320670 v-o ^

o) 6320667 c •NRTK •Static 6320664 4

6320661 /.i^nJ

6320658 1 1 1 1 ^ 0 200 400 600 800 1000 1200 1400 Epoch

Northing on BTJ, first session. APPENDIX

590687.5

590687.0 - O) c (0 •NRTK <0 lU •Static 590686.5 -

590686.0 0 100 200 300 400 500 600 700 800 Epoch

Easting on BTJ, second session.

6320676

6320673 cOi !E •NRTK r o •Static

6320670 -

6320667 - — [ 1 ^ 1 ^ 1 ——T- 1 0 100 200 300 400 500 600 700 800 Epoch

Northing on BTJ, second session. APPENDIX

590687.0

590686.5

O) 590686.0 (0 •NRTK (0 •Static ^ 590685.5

590685.0

590684.5 0 100 200 300 400 500 600 700 800 Epoch

Easting on BTJ, third session.

6320676

6320673 ^ O) !E •NRTK r 6320670 - o •Static

6320667 -

6320664 r—— ^ [ I 1 1 1 0 100 200 300 400 500 600 700 800 Epoch

Northing on BTJ, third session. APPENDIX

592481.0

592480.5

O) c ••g 592480.0 •NRTK (0 lU •Static

592479.5

592479.0 0 100 200 300 400 500 600 700 Epoch

Easting on KNWL, first session.

6320427

6320424

O) 6320421 - •NRTK O •Static 6320418

6320415

6320412 0 100 200 300 400 500 600 700 Epoch

Northing on KNWL, first session. APPENDIX

592482.0

592481.5 -

O, 592481.0 ^

•NRTK 0) CO •Static ^ 592480.5

592480.0 - ¿MT

592479.5 0 200 400 600 800 1000 Epoch

Easting on KNWL, second session.

6320421

6320418 -

O) c •NRTK 'E 6320415 - n •Static o

6320412

6320409 0 200 400 600 800 1000 Epoch

Northing on KNWL, second session. APPENDIX

592481.5

592481.0 O) 'iw •NRTK (0 lU(0 •Static 592480.5 -

592480.0 200 400 600 800 1000 Epoch

Easting on KNWL, third session.

6320418

O) c !E •NRTK t •Static o z

6320415 —,„, I I I 1 " ' I I ' 't 100 200 300 400 500 600 700 800 900 Epoch

Northing on KNWL, third session. APPENDIX

588362.5

588362.0 -

O) c '•g 588361.5 •NRTK (0 liJ •Static

588361.0

588360.5 1 —1 1 200 400 600 800 1000 1200 Epoch

Easting on PNY, first session.

6320970

6320967 Oi c !E •NRTK •C o •Static

6320964 -

6320961 200 400 600 800 1000 1200 Epoch

Northing on PNY, first session. APPENDIX

588362.5

588362.0 -

O) 'ic •NRTK (0 (0 •Static UJ

588361.0 -

588360.5 -1—— , —— 200 400 600 800 Epoch

Easting on PNY, third session.

6320970.0

O) c •NRTK !E 6320967.0 - •C • Static o

6320964.0 200 400 600 800 Epoch

Northing on PNY, third session. APPENDIX

588726

588720 +

588714

588708 •NRTK OT Uj 588702 •Static

588696

1 r

588684 1 1 • 1 I 0 200 400 600 800 1000 1200 1400 Epoch

Easting on PP, first session.

6321009

6321006 Kk CD ) •NRTK B 6321003 •Static ZO

6321000

6320997 0 200 400 600 800 1000 1200 1400 Epoch

Northing on PP, first session. APPENDIX

588725

588720

588715

588710 D) C ••g 588705 •NRTK (0 lU •Static

588700

588695 .

588690

588685 0 100 200 300 400 500 600 700 800 900 Epoch

Easting on PP, second session.

6321006

6321003 O) •NRTK •Static

6321000 -

6320997 0 100 200 300 400 500 600 700 800 900 Epoch

Northing on PP, second session. APPENDIX

588033.0

O) •NRTK 0) (0 •Static liJ

588032.5 I I 0 200 400 600 800 1000 1200 Epoch

Easting on PTK, first session.

6321132

O) c •NRTK £ 6321129 •Static o

6321126 H 0 200 400 600 800 1000 1200 Epoch

Northing on PTK, first session. APPENDIX

588033.0

•NRTK •Static

588032.0 0 200 400 600 800 1000 Epoch

Easting on PTK, second session.

6321135

6321132 - O) c •NRTK !rE o • Static z 6321129 WJV^

6321126 0 100 200 300 400 500 600 700 800 900 Epoch

Northing on PTK, second session. APPENDIX

APPENDIX B

11. Network RTK Simulation from SLA II.l. Baseline Result of Epoch by Epoch Processing

6202.95

6202.90 -

•NRTK 0) •Static <(08 6202.80 m

6202.75 -

6202.70 100 200 300 400 Epoch

Baseline SKEP-15399, first session.

Baseline error SKEP-15399, first session. APPENDIX

6202.95

6202.90

6202.85 - 0) .E 6202.80 •NRTK I 0) •Static I (0 DO 6202.75

400

Baseline SKEP-15399, second session.

0.15

E 0.10

o •NRTK UJ n 0.05 0) •Static c 0) 0) J-,., CSD 0.00

-0.05 50 100 150 200 250 300 350 Epoch

Baseline error SKEP-15399, second session. APPENDIX

Baseline SLOY-1648, first session.

Baseline error SLOY-1648, first session. APPENDIX

8962

8961 0) c •NRTK 0) •Static (0 ffl 8960

8959 100 200 300 Epoch

Baseline SLOY-1648, second observation.

Baseline error SLOY-1648, second observation. APPENDIX

II.2. Point Result of Epoch by Epoch Processing

1525095

O) •NRTK (0 (0 •Static LU V

1525094 100 200 300 400 Epoch

Easting on 15399, first observation.

6191417

6191416 O) c •NRTK !E t: •Static o z 6191415

6191414 J 0 100 200 300 400 Epoch

Northing on 15399, first session. APPENDIX

1525095

O) 'Netwok RTK in CO •Static lU

1525094 0 100 200 300 400 Epoch

Easting on 15399, second session.

6191416

O) c •NRTK !E 6191415 tL •Static o z

6191414 100 200 300 400 Epoch

Northing on 15399, second session. APPENDIX

1533040

1533039 -

O) 1533038 •NRTK (0 (0 •Static lU 1533037

1533036 IT

1533035 100 200 300 Epoch

Easting on 1648, first session.

6189444

6189443 -

g 6189442 •NRTK •c •Static o 6189441 -

6189440

6189439 50 100 150 200 250 300 Epoch

Northing on 1648, first session. APPENDIX

1533038

1533037 ^

O) c •NRTK (0 1533036 (0 •Static LU

1533035

1533034 100 200 300 Epoch

Easting on 1648, second session.

6189446

6189445 -

6189444 O) 1 ^ 6189443 •NRTK O •Static Z

6189442

6189441

6189440 100 200 300 Epoch

Northing on 1648, second session.