Mapping of Maldives Using Aerial Photography and Digital Photogrammetric Techniques

MAPPING OF MALDIVES USING AERIAL PHOTOGRAPHY AND DIGITAL PHOTOGRAMMETRIC TECHNIQUES

V. Raghu Venkataraman*, K. Kalyanaraman, Dr. K. Radhakrishnan, Dr. R.R Navalgund, P. Srinivas*, PVSSN Gopalakrishna, CVKVP Jagannadha Rao, K. Srinivasa Rao, G. Srinivas, P. Shashivardhan Reddy, J. Narendran, CS Narsimham, Dr. K. Venugopala Rao.

AERIAL SERVICES & DIGITAL MAPPING AREA

National Remote Sensing Agency, Department of Space, Govt. of India,

Balanagar, Hyderabad – 500037, India

Corresponding author 1 - P. Srinivas

e-mail: [email protected]

National Remote Sensing Agency,

Department of Space, Govt. of India,

Aerial Services & Digital Mapping Area,

Balanagar, Hyderabad – 500 037

Andhra Pradesh, INDIA

Telephone Nos. 0091 040 23884489 (O)

Fax No. 0091 040 23884483

Corresponding author 2 - V. Raghu Venkataraman

e-mail: [email protected]

Telephone Nos. 0091 040 23884470/71 (O) Abstract

Republic of Maldives is located in the Indian Ocean about 300 miles south of

India and 450 miles south west of Sri Lanka consisting of 26 atolls with 1192 islands scattered between 1º S to 8º N latitude, 72º E to 74º E longitude with 99

% of the area being water.

The objective of this project was to prepare digital maps of the entire country in

1:25,000 scale using aerial photographs acquired in 1:40,000 scale in a single coordinate system. Remote sensing satellite data was acquired for preliminary reconnaissance of the terrain and selection of reference and base stations for continuous Global Positioning System (GPS) observations to establish reference datum in WGS 84. Thereafter, flight operations for aerial photography were carried out with automated Computer Controlled Navigation System (CCNS).

Digital photogrammetry techniques with Kinematic GPS data and pre pointed

GPS control survey data was utilized for aero triangulation, block adjustment and vector capture.

The large scale mapping for 16 select islands of Maldives was carried out in

1:1000 scale using 1:6000 scale aerial photographs.

Keywords: Aero triangulation, Digital photogrammetry, GPS, Reference station,

CCNS. 1. INTRODUCTION

The Republic of Maldives consists of an archipelago of 1192 islands scattered over a distance of 870 km in the North–South direction and about 150 km in the

East-West direction between 0º42’30”S to 7º6’30” N latitude, 72º32’30” E to

73º46’15” E longitude. It is located in the Indian Ocean about 480 km South of

India and 725 km South West of Sri Lanka.

The islands are grouped in the form of atolls. An atoll is a coral island consisting of a circular belt of corals enclosing a central lagoon. Maldives consists of 26 atolls. The atolls and islands are scattered and spread across an area of 100 000 sq. km. area, 99% of which is water and less than 1% covers land portion. Only

33 islands have a land area of more than 1 sq. km and one third of all the inhabited islands have fewer than 500 people.

Earlier, different organizations have attempted and prepared very small scale maps for navigation but large scale maps of atolls and islands could not be prepared due to non availability of appropriate technology. With the advent of

Global Positioning System (GPS) and photogrammetry techniques coupled with stereo aerial photography the potential for digital mapping in a single reference frame work was realized through a collaborative project between the Government of India (GoI) and the Republic of Maldives. This paper attempts to provide a comprehensive picture of the methodology, technology and processes involved in the execution of the project by the National

Remote Sensing Agency (NRSA), Hyderabad an organ of the Department of

Space (DOS), GoI. 2. BACKGROUND

In 1999, Honorable Mr. Ibrahim Hussein Zaki, Minister for Planning and National

Development, Government of Maldives had discussions with the High

Commissioner of India, Hon’ble Mr. Kanwar Singh Jasrotia regarding the possibility of digitally mapping the archipelago and establishing of a remote sensing unit in his country. Thereafter the Maldivian authorities sent a request for this purpose. The GoI responded to this request with a project proposal which was shared with the Maldivian authorities.

The President of Maldives H.E. Mr. Maumoon Abdul Gayoom, during the state visit to India in August, 2000, had evinced keen interest in the work carried out by

NRSA and requested follow up action on the above mentioned project proposal.

Based on the request from the Maldivian authorities, The Ministry of External

Affairs (MEA), GoI approached DOS and asked for a detailed project proposal for consideration by both the Governments. Accordingly the project proposal was prepared by NRSA for further consideration and implementation. 3. PROJECT OBJECTIVES

NRSA was awarded the project “Digital Mapping of The Republic of Maldives” by the MEA. The project consisted of:

3.1 Preparation of digital maps on 1: 25 000 scale using 1: 40 000 scale aerial

photographs for entire Maldives in a single reference frame with Universal

Transverse Mercator (UTM) coordinates.

3.2 Preparation of digital maps on 1: 1 000 scale using 1: 6 000 scale aerial

photographs for 16 selected islands.

3.3 Establishment of a Remote Sensing Centre at Male, Maldives 4. AVAILABILITY OF MAPS

It was reported that metric charts of Maldives published in 1993 covering the whole of Maldives on a scale of 1:300 000 were available as given below:

 Maldives Sheet 1 : Addu Atoll to North Huvadhoo

 Maldives Sheet 2 : North Huvadhoo Atoll to Mulaku Atoll

 Maldives Sheet 3 : Mulaku Atoll to South Maalhosmadulu Atoll

 Maldives Sheet 4: South Maalhosmadulu Atoll to Thavndhippothu Atoll.

These charts are the updated version using aerial photos taken by Royal Air

Force (RAF) of UK in 1968 and 1969 and satellite imagery acquired between

1984 and 1988. These 1:300 000 charts were of not much of use to for detailed development planning as the Islands of Maldives are very small, ranging from 0.5 sq. km. to 2 sq. km. In addition, 8 sheets on 1:250 000 scale based on UTM projection were also available, but these maps also lacked much of the required details in terms of size and land area of the islands.

In the course of execution of this project, the 4th edition of the “Atlas of the

Maldives”, (ISBN 1 876410 42 6) published in 2004 by Atoll Editions, PO Box

113, Apollo Bay, Victoria, 3233, Australia was extensively used as a reference document.

5. METHODOLOGY

The methodology for the preparation of digital maps (Paul R. Wolf and Bon A.

Dewitt) on 1:25 000 scale and 1:1 000 scale involved the following processes as indicated in Fig. 1 and Fig. 2 respectively.

5.1 Flight planning of aerial photography operations.

5.2Aerial Photography in 1: 40 000 scale and 1: 6 000 scale (for few selected

islands) with Kinematic GPS (KGPS) observation

5.3GPS observations on Reference stations (13 Nos.) and pre-targets (41

Nos.) of size 5m x 5m for establishment of reference frame in WGS 84

datum for entire Maldives

5.4Processing of aerial exposed film rolls & annotations of processed film rolls at

Photo processing lab at NRSA.

5.5Ground control survey for few selected islands on 1: 6 000 aerial photographs

5.6Post processing of airborne Kinematic GPS data and static GPS reference

stations and other ground control points. 5.7Scanning of aerial film rolls using precision photogrammetric scanner @ 21

microns for 1: 40 000 scale aerial photographs and @ 20 microns for 1: 6

000 scale aerial photographs.

5.8Aero triangulation (densification of ground control points) using softcopy /

Digital Photogrammetry systems.

5.9Digital Mapping on 1: 25 000 / 1: 1 000 scale using Photogrammetry systems

for plotting and subsequent use in Geographic Information System (GIS)

environment.

5.10 Field verification / data collection for few selected islands and other atolls

on 1: 1 000 scale and 1: 25 000 scale map sheets respectively.

5.11 Quality control of digital maps 6. RATIONALE FOR METHODOLOGY FOR 1:25 000 SCALE MAPS

The methodology for mapping in 1:25 000 scale was arrived at based on the required map content and need to have a country wide coordinate system.

6.1 Requirements

The most challenging requirement was of course the need to have a single grid coordinate system for the entire country.

As regards content, essentially the 1:25 000 scale maps had to show the extent of the land area in terms of both shape and size clearly demarcating the land and water boundary, atolls, built up areas, roads, and vegetation.

As regards coordinates and projection, the need was to accurately depict the position of the islands in the country wide grid. This would automatically give the positions of the islands relative to each other and the distances between them.

6.2 Data sources

B & W stereo aerial photography in 1:40 000 scale was selected as the primary data source because it would provide a spatial resolution of about 100 cm which is adequate for demarcating the required content layers. The option of utilizing high resolution satellite data with 100 cm resolution was also thought of but discarded since the data comprising of about 800 scenes of entire 100 000 square km area would have to be sourced as the frame sizes are normally of 10 km x 10 km size. Aerial photography provided the twin advantage of economic and selective data acquisition covering only those areas where the proportion of land was significant as well as providing stereo data for generation of height information. RMK 15/23 camera was selected as it would provide metric quality photographs with wide swath to reduce overall flying time.

For the purposes reconnaissance for aerial photography and GPS based control survey, LISS III sensor imagery of IRS 1C-1D was selected as the imagery with a resolution of 23 m and in color clearly show the relative positions of the islands along with the shape and size of the islands.

Since it would be virtually impossible to get required controls using traditional methods due to the vast expanses of water the only option was to use GPS controls. The GPS points were pre-signalized so as to be able to be identified on the aerial photos.

To derive full benefit of the availability of Kinematic GPS data for the aircraft platform for initial estimation of the frame centre coordinates.

6.3 Data processing and mapping

Since the primary data was on film it was decided to convert it to digital form using high quality photogrammetric scanner. It was also decided to utilize digital photogrammetrc techniques for aero triangulation and block adjustment since analytical systems were obsolete and a certain level of automation was inherently available for point selection.

Once the primary data is oriented in such to the correct direction and block adjustment completed, the process of vector capture in the mapping environment, comprising of PC based low cost systems, was selected for yielding the line maps with appropriate symbols so that multiple systems could be deployed. 7. RATIONALE FOR METHODOLOGY FOR 1:1 000 SCALE MAPS

7.1 Requirements

The main requirement was content. 1:1 000 scale maps had to show each individual building and built up features very clearly along with the land area utilized and the distances between features have to be accurate within 25 cm besides the extent of the land area in terms of both shape and size.

7.2 Data sources

B & W stereo aerial photography in 1:6 000 scale was selected as the primary data source because it would provide a spatial resolution of better than 10 cm which is adequate for demarcating the required content layers. Stereo data was critical for accurately mapping buildings.

To derive full benefit of the availability of Kinematic GPS data for the aircraft platform for initial estimation of the frame centre coordinates.

7.3 Data processing and mapping

Since the primary data was on film it was decided to convert it to digital form using high quality photogrammetric scanner.

It was also decided to utilize digital photogrammetric techniques for aero triangulation and block adjustment since analytical systems were obsolete and a certain level of automation was inherently available for point selection. 8. FLIGHT PLANNING

Flight planning was an important and critical component for this project since most of the area is covered by water. Information from various sources such as satellite images, existing atlas maps of Maldives, old maps etc., was used to prepare optimized flight plans so as to make flying economical and minimize wastage of both flying time and aerial film. This was especially critical as the window of opportunity comprising of cloud free season over the area is extremely limited. The imagery from LISS-III sensor of Indian Remote Sensing Satellites

(IRS 1C/1D) for the entire area was used for preliminary reconnaissance and flight planning. The above IRS imagery were also utilized for identification of suitable locations for the GPS reference stations and Ground Control Point

(GCP) pre signalized targets in an economical manner. The World Wide Mission

Planning (WWMP) software was used for flight planning.

The entire country was divided into seven geographical blocks for planning, managing and execution of the project as shown in Fig. 3 for aerial photography in 1: 40 000 scale. The runs were planned for some blocks in N-S direction and for some blocks in E-W direction depending on the shape of the block. Besides the main runs, tie lines were also planned for each block in oblique direction.

Since the land portion was less the number of tie lines planned was much more than in normal situations. The intersection of main lines and tie lines in the flight plan was made in such a way as to fall in as many islands as possible. The details of the flight plans are given below in Table 1 9. AERIAL PHOTOGRAPHY OPERATIONS

Aerial photography (Black & White) was carried out using Beech Super King Air

B-200 (Fig. 4) mounted with Zeiss RMK15/23 metric camera and integrated with

INS and Kinematic GPS. The aircraft is guided by Computer Controlled

Navigation System (CCNS) software for carrying out aerial photography very accurately. The camera is tightly coupled with CCNS that in turn connected to airborne GPS.

After interactive checks and corrections of the software-generated flight lines, the data is stored on a PCMCIA card. The aircrew was also provided with this flight planning information in hard copy form. During aerial photography this data is transferred to the on board computer. The aircraft navigation is carried out with the assistance of CCNS4, which is supported by GPS a satellite navigation system. At the precise moment that an aerial photo is exposed, the position of the aircraft can be determined by evaluating the signals from, at a minimum, four satellites. In addition to computer controlled navigation, aircraft position at the precise moment of shutter release can be determined by a ground station using

Kinematic GPS (KGPS). After completion of aerial photography, the recorded coordinates of the camera’s projection centres are read into Bentley’s MicroStation

CAD software using a standard interface and then plotted out as flight line indices. The CCNS is a guidance, positioning and management system for aerial survey flight missions. The basic system consists of the Central Computer Unit (CCU), the 5'' TFT Command and Display Unit (CDU), and necessary cabling and mounting. Optional equipment completes the system to fulfill specific requirements. The system is universally usable and can operate and integrate all

Wild/Leica, Zeiss respectively. Z/I Imaging aerial camera systems. It provides a complete and comprehensive solution for mission planning and documentation, aircraft guidance and sensor management during missions. CCNS controls the camera and other sensors, including crab/drift setting(s), forward overlap, V/H computation and provides data for data annotation on film; the co-ordinates may be WGS84 or the countries X/Y co-ordinates (optional).

The CCNS brings the advantages of a glass cockpit and a fully automated flight control system to aerial surveying and reconnaissance. All operations are activated via one knob and four buttons. The EFIS type display, which is operated like an aircraft instrument, is divided into guidance and system/sensor management information (right side of the display). The pilot just has to "follow the needle". Outputs, with selectable sensitivity for HSI, VDI and CDI instruments, are provided.

The camera used in this project is RMK aerial survey camera System. It features a systematic, modular design with individual components forming logical functional units optimized for both practical application and economical use. The RMK features high-performance lenses with internal filters, which significantly enhance image quality and a unique pulsed rotating-dish shutter. It is Ideal for

GPS/INS - supported navigation and aero triangulation. It also has eight point- shaped fiducials in the corners and midway along the edges, numbered 1 to 8, spacing 113 mm, point diameter 100 µm, cross lines with 50 µm line thickness, exposed at midpoint of exposure.

The flight operations were carried out during the month of February, 2004 as that was the ideal cloud free season over Maldives. Aircraft was ferried from

Hyderabad to Male via Trivandrum. Permission from the Director General of Civil

Aviation (DGCA), GoI was taken prior to departure as per the regulations for ferry flight to Male without licensed Navigator and for YA number was YA/N

538/01/30094. Civil Aviation Department of Maldives issued clearance letter to

Maldives airports authorities for entry into Maldivian airspace vide Permit no. is

CAD-VRMM/LP-IEXT/04/32.

The aircraft was mobilized only with crew, maintenance engineers, equipment and film. Camera system engineers, GPS survey team and coordinators were mobilized via civil airlines.

After the flight planning was completed hard copy print outs were taken for reference. Two PCMC cards with flight planning data were provided for loading on to the aircraft CCNS which was loaded and checked prior to departure. Aircraft readiness was also checked at the base. The SKA B-200 aircraft has a mandatory 100 hour inspection to be carried out at base with hanger and stores facility. The volume of flying effort involved in terms of flying time was carefully estimated including main ferry, local ferry, actual operations and alignment/ turn times. This was optimized to approximately 95 hours by avoiding water areas so that the aircraft could mobilize to Maldives after 100 hour inspection at

Hyderabad and complete the entire task without having to interrupt for coming base to base for inspection. To ensure snag free performance spare tyres and

A total of 25 film rolls of 240 mm format each having a capacity of exposing 275 frames was drawn from the refrigerated stores and loaded into the aircraft for mobilization. At Male the film rolls were unloaded and kept in a safe custody in air-conditioned environment to prevent degradation of film due to heat.

Aerial photography operations were carried out from Male international airport as the base. Sorties were carried out in such a manner that the local ferries were made productive for tie lines.

10. GPS SURVEYS

10.1 Reference stations

Thirteen GPS reference stations spread over the entire Republic of Maldives in different blocks for the project were used for airborne GPS assisted aerial photography for the establishment of reference network (Sapporo, July 2003 & Tomas Soler, Lucy W.Hall and Catherine K. Reed., 1998) in WGS-84 and pre- target GCPs in tandem as shown in Table 2. The reference stations were located in such a way that at least one reference station was there in one-degree grid.

Each reference station was occupied with geodetic grade dual frequency GPS receivers for a minimum of three days for duration of 12 hours from 6 AM to 6 PM every day. The Male International GNSS Services (IGS) station was also occupied as part of this GPS campaign. A permanent monument was established at each reference station site.

10.2 Pre-target base stations

Forty two pre-target GCPs spread over the entire country were installed in place and GPS survey of the points was carried out as shown in Table 3. The pre- target GCP designed was 5m X 5m in dimension with plus mark in white and remaining quadrant area in black as shown in the Fig. 5. Each pre-target GCP was occupied continuously with a geodetic grade GPS receiver for duration of 3 hours simultaneously with the GPS reference station as shown in the Fig. 6.

The land area of Republic of Maldives is spread over 100 000 Sq. Km. The planning of aerial photography, deployment of personnel for reference station operations and pre target surveys involves meticulous planning, coordination and implementation of the plan. Most of the islands in Maldives are uninhabited and locating natural and man-made features are next to impossible, hence pre signalization was carried out before the aerial photography. The major portion of the country is covered with water and the numbers of airports were less, hence deployment of personnel at different GPS locations by traveling very long distance on open sea was an Herculean task. The following map as shown in the

Fig. 7 depicts the planning carried out in the deployment of the personnel at different GPS sites.

10.3 GPS Data processing

The GPS data pertaining to the reference station is processed in a Bernese scientific post processing software, which is capable of processing long baselines and the coordinates of the reference stations are computed using the GPS data from the nearest IGS stations namely Bangalore (India), De Garcia (Indian

Ocean), NTUS (Singapore), Bahrain etc. The coordinates of Pre-targets was derived by processing the GPS data collected at Pre-targets with reference to the nearest reference stations using SKIPRO software in differential mode.

11. PATH RECOVERY, SCANNING OF AERIAL PHOTOGRAPHS, AERO TRIANGULATION AND BLOCK ADJUSTMENT

The path recovery of aerial photographs was a Herculean task. It involved retrieving the aerial photos as per the planned flight plans and recee reports

(prepared by pilots on the day of aerial photography). Since 99% of the entire

Republic of Maldives is covered with water, identifying and segregating of aerial photographs as per the recee report and flight plans was a very difficult task. This was very important to reduce the volume of effort in scanning of the aerial photographs. The scanning of aerial photographs was carried out using very high precision

Zeiss SCAI Photogrammetry scanner and aerial photographs in 1: 40 000 scale were scanned at 21 microns. The scanning was executed very carefully by applying enhancements since the terrain was very difficult and sun light was varying from one part of the atoll to another. The pre-targets placed on the ground were identified as shown in Fig. 8 and checked with the flight plan. Thus only 2377 out of the total 4456 frames representing 53 % of the frames were scanned. At an average daily productivity of 20 frames per day, this optimization resulted in saving about 100 days in the time schedule. These digital images were used for automatic aerial triangulation and block adjustment.

Triangulation is defined as the extension or densification of control within the block. Block adjustment depends on the distribution of GCPs, quality of GCP, type of terrain, quality of image (for generation of tie points by image matching) and the proper analysis of the block. The sigma defines the accuracy of the block

The scanned aerial images were input to the aero triangulation along with camera calibration report, processed DGPS data and processed KGPS data.

Triangulation was carried out using high-end Photogrammetry system consisting of Socetset software along with Orima block adjustment software. Automatic aero triangulation with an autonomous batch process by selecting pre-selected tie points and appropriate matching strategy was used in this project. Aero triangulation was performed with different strips composed of both parallel and cross strips covering seven blocks. Utilization of Digital Photogrammetry Work

Station (DPWS) with automation in triangulation and bundle block adjustment had reduced the processing time and expensive manpower otherwise required for analytical aerial triangulation. The project file was set up in Socetset with all the scanned images and calibration parameters such as calibrated focal length, fiducial mark coordinates, Principle Point coordinates, radial distortions etc.

Automatic IO was carried out in batch mode by image correlation with the fiducial templates available for RMKTOP camera.

The use of GPS derived antenna positions during the photo acquisition had considerably improved the performance of the aerial triangulation process as well as reduced the number amount of ground control points in the field (C.S.Fraser,

1994). Since the land portion is 1% of the total extent of the Maldives, enough

GCPs (pre-targets) could not be placed. The exposure coordinates of each frame was taken as primary control and given more weight age for the block adjustment as compared to the Pre-target GCPs. The ground control points used for the block adjustment were the pre-targets, reference stations and processed KGPS data.

The other inputs for this project such as camera calibration file, flight plan index, overlaps, image scale and image sequences were used for initial approximation of the block. GPS camera stations are used for the stabilization of the block. The results of block adjustment are based on the average image precision measurement of 0.5 to 1 pixel.

The triangulation of aerial photographs in 1: 40 000 scale was carried out for individual blocks as shown in the Fig. 3. However for aerial photographs in 1:

6000 scale, the triangulation was carried out island wise and adjusted accordingly. The GCPs were acquired by our team for selected islands in the difficult terrain conditions. The nearest reference station was taken as the base station and the GPS survey was carried out in the same coordinate system reference schema. The results of aerial triangulation for all the blocks are tabulated as shown in the Table 4. 12. REFERENCE GRID

A reference grid has been designed for covering the entire Maldives with 1:25

000 scale maps. The reference grid is in UTM projection. The grids are of 10 000 m (10 km) interval. The Latitude and Longitude values are also available in

Degrees, Minutes & Seconds for which the gridlines are drawn for 1 degree, 15 minutes and 7 ½ minutes intervals.

The numbering schema for the entire Maldives on 1: 250 000, 1: 50 000 and 1:

25 000 scale maps are shown in Fig. 9, Fig. 10 & Fig. 11 respectively. The numbering schema derived for 1: 25 000 scale maps is as per the International

Map World (IMW) series. In Maldives most of the area is in northern hemisphere above the equator and a small portion part of the area falls in southern

Hemisphere, below the equator. To have positive coordinate value in North direction, the origin was shifted to the Southern Hemisphere. The zone number

43 (Southern hemisphere) was taken for processing the GPS coordinates with

UTM projection. The datum (vertical reference) for the mapping is with respect to

WGS 84. 13. LAYER LIST

The data is captured in different layers as per the feature (layer list), which aides in importing the data into GIS environment. The list of maps in 1:25 000 which actually cover land or atoll portion (no deep waters) is as given below as shown in Table 5. List of islands for which 1:1 000 scale maps were prepared and are listed below in Table 6. The layer list used for the preparation of maps in 1: 25

000 scale for entire Republic of Maldives & 1: 1 000 scale for selected islands are listed in the Table 7. 14. GIS DATABASE

Maldives GIS database has been created at 1:1 000 scale and 1:25 000 scale using object oriented technology with open GIS standards in ArcGIS environment. In order to have compatibility with base maps in AutoCAD format, the GIS data models were developed with same spatial reference system including datum, projection and spatial extent.

To facilitate nation wise as well for island wise GIS applications such as censes, utilities (water supply, sewerage, gas, communication, power, environmental, agriculture, fisheries, navigation, national security, transportation) and revenue a seam less GIS data model was developed.

Keeping GIS database volume and optimization, it is proposed to develop the data structures as personal GIS geodatabase, which uses the Microsoft access to store the both spatial and non-spatial database. The developed GIS database can be scalable to enterprise GIS database using Relational Data Base

Management (RDBM) software like oracle, once the GIS applications developed over this as mentioned above. 15. ESTABLISHMENT OF REMOTE SENSING LAB AT MALE

The establishment of Remote Sensing Centre at Male, Maldives involved the following:

15.1 Procurement of digital image processing system, digital photogrammetry

system, GPS receivers & GIS system. All the hardware and software

modules were tested at NRSA.

15.2 Training of personnel of Maldives for the period of 4 to 6 weeks at NRSA.

This phase of training was carried out in November / December 2004 for 4

Maldivian officials

15.3 Submission of digital maps. The final maps including orientation files,

images etc has been copied in the systems at Maldives and NRSA

officials had demonstrated the usage of the maps for different

applications.

15.4 Installation of systems at the full fledged remote sensing unit with all the

hardware and the software as shown in Table 8 at Male, Republic of

Maldives during April 2006 with on site training on the systems with the

populated with digital maps. 16. CONCLUSIONS

The aerial photography along with the establishment of reference datum in WGS-

84 was carried out for the first time for entire Republic of Maldives. Mapping in 1:

25 000 scale for entire Maldives and large scale mapping in 1: 1000 scale for a few selected islands are the landmark. The whole task including the establishment of remote sensing centre at Male was completed within the stipulated project time as planned and the timeline for the individual activities is as shown in Fig. 12.

17. ACKNOWLEDGEMENTS

We acknowledge our sincere thanks to the DOS, GoI for giving us the opportunity to take up this project. We also acknowledge our thanks to MEA for funding and awarding the project to DOS.

We extend our sincere thanks to Dr. RR Navalgund, Director SAC who had extended his full support in planning and executing the project in his capacity as

Director, NRSA. We also extend our warm thanks to Director, NRSA Dr. K.

Radhakrishnan for his guidance in establishing a remote sensing centre at Male,

Maldives.

We acknowledge the contribution of all the other personnel involved in the project mainly (i) pilots Capt. AL Hannurkar and Capt SMH Mehdi, (ii) Navigator Wg.

Cdr. (retd) Dalbir Singh, (iii) Aircrew engineers, field survey personnel and photogrammetrists Shri B. Laxman, Mrs. I Jayalakshmi, Shri P. Krishnaiah, Shri B. Sadasiva Rao, Shri Anantha Padmanabha, Shri M. Sreedhar, Shri NMS

Reddy, Shri D. Syama Rao, Shri G. Anil Kumar, Shri Y. Srinivasa Rao, Mrs. M.

Udayalakshmi, Mrs. TE Rani, Shri P. Srinivas Reddy, Shri G. Devender Rao, Shri

K. Krishna and Shri Ashutosh Bharadwaj.

18. REFERENCES

 Paul R. Wolf and Bon A. Dewitt, Elements of Photogrammetry

 Sapporo, The Royal Thai Survey Department - A report on the Geodetic

work (1999 – 2002) at the XXIII General Assembly of the International

Union of Geodesy and Geophysics during 30 June – 11 July, 2003.

 Tomas Soler, Lucy W.Hall and Catherine K. Reed., 1998, -

Establishment of a GPS High accuracy Reference Geodetic Network in

the Caribbean, Surveying and Land Information System, Vol. 58, No. 1,

1998, pp 13-24.

 C.S.Fraser, - GPS Aerotriangulation – in sights from Angledool project.,

Aust .j.Geod. Photogram.Surv, No.61, December, 1994, pp 1 – 16. List of Tables

Table 1: Flight Plan Details for 1:40 000 scale photography

Table 2: GPS Reference Station for Airborne GPS

Table 3: GPS Reference & Target / Rover Stations

Table 4: Results of Aerotriangulation of entire Maldives shown as blockwise

Table 5: List of maps for entire Maldives in 1: 25 000 scale

Table 6: Name of the selected islands in 1: 1 000 scale

Table 7: Layer list for the preparation of 1: 25 000 & 1: 1 000 scale mapping

Table 8: List of hardware and software established at Male, Maldives Table 1 Flight Plan Details for 1:40 000 scale photography

Block Number of No. of Approx. No of frames as No. of frames No. of Number Main Run tie lines number of per tie line actually exposed Photos lines and frames per selected for direction run scanning

1 40 E-W 31 11-41 5-24 1635 989

2 9 N-S 8 41-68 8-11 626 311

3 11 N-S 22 84 5-12 1121 313

4 15 E-W 8 21-32 7-16 473 365

5 15 E-W 8 29 8-13 516 357

6 1 0 4 4 4

7 5 E-W 2 13 8 81 38

Total 4456 2377

Table 2 GPS Reference Station for Airborne GPS

Sl. No. Reference Station Block 1 Hanimaadhoo 1 2 Alifushi 1 3 Rasdhoo 2 4 Nilandhoo 2 5 Kaashidhoo 3 6 Male 3 7 Kolhufushi 3 8 Veymandoo 4 9 Kadhdhoo 4 10 Kaadehdhoo 5 11 Gemanafushi 5 12 Fuvamullah 6 13 Gan (South) 7 Table 3 GPS Reference & Target / Rover Stations

Block-1 Sl .No. Reference Station Target/ Rover Station 1 Hanimaadhoo Innafinolhu 2 Alifushi Kelaa 3 Kanditheemu 4 Makunudhoo 5 Feevah 6 Maafaru 7 Kothafaaru 8 Dharvandhoo 9 Thulhaadhoo 10 Goidhoo 11 Kanifushi 12 Maabinhuraa

Block-2 S.No. Reference Station Target/ Rover Station 1 Rasdhoo Thoddoo 2 Nilandhoo Feridhoo 3 Dhigurah 4 Hukurudhoo 5 Filitheyo 6 Hulhudheli 7 Kandinma 8 Kudahuvadhoo

Block-3 S.No. Reference Station Target/ Rover Station 1 Kaashidhoo Gaafaru 2 Male Reethirah 3 Kolhufushi Dhiffushi 4 Guraidhoo 5 Kunaavashi 6 Fotheyobodufushi 7 Raimandhoo 8 Thuvaru Block-4 S.No. Reference Station Target/ Rover Station 1 Veymandoo Buruni 2 Kadhdhoo Vilufushi 3 Kandoodhoo 4 Ishdoo 5 Maavah 6 Hithadhoo

Block-5 S.No. Reference Station Target/ Rover Station 1 Kaadehdhoo Kolamaafushi 2 Gemanafushi Vilingili 3 Fares 4 Gan

Block-6 S.No. Reference Station Target/ Rover Station 1 Fuvamullah Fuvamullah

Block-7 S.No. Reference Station Target/ Rover Station 1 Gan (South) Hithadhoo 2 Hulhumeedhoo 3 Gan

Table 4 Results of Aerotriangulation of entire Maldives shown as blockwise

Block Scale of No. of No. of Pixel σ0 Empirical accuracy No. Photography images GCPs size(µm) (µm) (RMS) of GCPs

µX (cm) µY (cm) µZ (cm)

1 1: 40,000 824 13 21 10 29.2 15.4 18.3

2 1: 40,000 262 6 21 10 21.8 12.0 14.4

3 1: 40,000 458 9 21 10 25.2 8.5 3.5

4 1: 40,000 238 7 21 10 12.8 11.4 25.9

5 1: 40,000 260 4 21 10 5.6 1.6 4.3

7 1: 40,000 32 3 21 10 2.6 2.0 1.0 Table 5 List of maps for entire Maldives in 1: 25 000 scale

Block Sl. Number Map Sheet Number Total 1 1-2 43N 01 P SE, SW 1 3-6 43N 02 K NE, SW,SW,SE, 1 7-9 43N 02 M NE, NW,SE 1 10-12 43N 02 N NE, SW, SE 1 13-15 43N 02 O NE, NW, SE 1 16 43N 02 P NE 1 17-19 43N 03 M NE, SW,SE 1 20-23 43N 03 N NE, NW, SW, SE 1 24-27 43N 03 O NE, NW, SW, SE 1 28-31 43N 03 P NE, NW, SW, SE 1 32-35 43N 04 M NE, NW, SW, SE 1 36 43N 09 D SW 1 37-40 43N 10 A NE, NW, SW, SE 1 41-42 43N 10 B NE, NW 1 44-47 43N 10 C NE, NW, SW, SE 1 48-51 43N 10 D NE, NW, SW, SE 1 52 43N 10 G SW 1 53-54 43N 10 H NW, SW 1 55-58 43N 11 A NE, NW, SW, SE 1 59-61 43N 11 B NE, NW, SW 1 62-64 43N 11 C NW, SW. SE 1 65-67 43N 11 D NE, NW, SW 1 68-71 43N 11 E NE, NW, SW, SE 1 72-74 43N 11 F NE,NW,SE 1 75-78 43N 11 G NE, NW, SW, SE 1 79 43N 11 J SW 1 80 43N 11 K NE, NW, SW, SE 1 84 43N 11 L NW 1 85-86 43N 12 A NW,SW 86 2 1 43N 04 K SE 2 2-3 43N 04 L NE,SE 2 4-6 43N 04 O NE,SW,SE 2 7-10 43N 04 P NE, NW, SW, SE 2 11-12 43N 05 I NE,SE 2 13-14 43N 05 J NE,SE 2 15 43N 05 K NE 2 16-19 43N 05 M NE,NW,SW,SE 2 20-23 43N 05 N NE, NW, SW, SE 2 24-27 43N 05 O NE, NW, SW, SE 2 28-31 43N 05 P NE,NW, SE 2 32-35 43N 06 M NE, NW, SW, SE 2 36-37 43N 06 N NE,NW 2 38 43N 12 C SW 2 39 43N 13 C SW 2 40-41 43N 13 D NW,SW 2 42-43 43N 14 A NW,SW 2 44 43N 14 B NW 44 3 1-2 43N 12 E NE,SE 3 3-5 43N 12 F NE,SW,SE 3 6-9 43N 12 G NE, NW,SW,SE 3 10-13 43N 12 H NE, NW,SW,SE 3 14 43N 12 I SW 3 15-17 43N 12 J NW, SW, SE 3 18 43N 12 K NE, NW,SW,SE 3 22-23 43N 12 L NW, SW 3 24-27 43N 13 E NE, NW,SW,SE 3 28-31 43N 13 F NE, NW,SW,SE 3 32-33 43N 13 G NE, NW, SE 3 35-38 43N 13 H NE, NW, SW, SE 3 39 43N 13 I NW 3 40 43N 13 J NW, SW, SE 3 43-46 43N 13 K NE, NW,SW,SE 3 47-49 43N 13 L NW, SW, SE 3 50 43N 13 O NW 3 51-54 43N 14 E NE, NW,SW,SE 3 55 43N 14 F NE 3 56-58 43N 14 I NE, NW, SW 58 4 1 43N 06 N SE 4 2-3 43N 06 O NE,SE 4 4 43N 06 P NE 4 5-6 43N 14 B SW,SE 4 7-10 43N 14 C NE, NW,SW,SE 4 11-12 43N 14 D NE,NW 4 13 43N 14 F SW 4 14-15 43N 14 G NW, SW 4 16-17 43N 14 H SW,SE 4 18-19 43N 14 L NW,SW 4 20 43N 15 A NE,SE 4 22-24 43N 15 E NE, NW,SW,SE 4 26-27 43N 15 I NW, SW 27 5 1 43N 08 N SE 5 2 43N 08 O NE 5 3-4 43N 16 A NE, SE 5 5-8 43N 16 B NE, NW,SW,SE 5 9-12 43N 16 C NE, NW,SW,SE 5 13-14 43N 16 D NE, NW 5 15-18 43N 16 E NE, NW,SW,SE 5 19-22 43N 16 F NE, NW,SW,SE 5 23-26 43N 16 G NE, NW,SW,SE 5 27 43N 16 H NW 5 28 43N 16 J SW 5 29-30 43N 16 K NW, SW 30 6 1 43M 09 F NE 1 7 1-4 43M 09 C NE,NW,SW, SE 4 Grand Total 250 Table 6 Name of the selected islands in 1: 1 000 scale

S. No. Island Name 1 NILANDHOO 2 FUNADHOO 3 MAAMIGILLI 4 NAIFARU 5 VILLIGILLI 6 GURAIDHOO 7 HUVARAFUSHI 8 GADHDHOO 9 MALE 10 K_FUNADHOO 11 HULHULE 12 KEDHIKULHUDHOO 13 MULI 14 HITHADHOO 15 HANIMAADHOO 16 FOAMMULAH 17 GAN (SOUTH)

Table 7 Layer list for the preparation of 1: 25 000 & 1: 1 000 scale mapping

Sl. Layer list Feature Remarks 1 BOUNDARY_ISLAND POLYGON 2 BUILDING_DUCT POLYGON 3 BUILDING_GROUP POLYGON 4 BUILDING_INDUSTRIAL POLYGON 5 BUILDING_SHED POLYGON 6 BUILDING_SINGLE POLYGON 7 BUILDING_UNDERCONSTRUCTION POLYGON 8 CANOPY POLYGON TREE_COVER 9 CULTIVATION POLYGON 10 FOUNTAIN_AREA POLYGON 11 LAGOON POLYGON 12 MARSHY_LAND POLYGON 13 PALMYRA_GROUP POLYGON 14 PARK POLYGON 15 PLANTATION POLYGON 16 PLATFORM POLYGON ELEVATED_SURFACE 17 PLAYGROUND POLYGON 18 POND POLYGON 19 ROAD_ISLAND POLYGON 20 STADIUM POLYGON 21 SWIMMING_POOL POLYGON 22 TANK POLYGON WATER_TANK(MANMADE) 23 TANK_CIRCULAR POLYGON 24 TANK_DRY POLYGON 25 TANK_OIL POLYGON 26 TANK_SQUARE POLYGON 27 WATER_TANK_SINTEX POLYGON 28 WELL_AREA POLYGON 29 BOAT_CHANNEL LINE 30 BUILDING_ELEVATION LINE CHANGE ELEVATED LINES 31 BUILDING_RIDGE LINE 32 DEEP_WATER_LINE LINE 33 DRAIN LINE 34 EMBANKMENT LINE 35 FENCE LINE 36 FOOTBRIDGE LINE 37 HEDGE LINE 38 HELEPAD LINE 39 JETTY LINE 40 PARKING_AREA LINE 41 PIPELINE LINE 42 PROTECTED_WALL LINE 43 ROAD_BLACKTOP LINE 44 ROAD_BLACKTOP_CENTER LINE 45 ROAD_BRIDGE LINE 46 ROAD_CARTTRACK LINE 47 ROAD_CARTTRACK_CENTER LINE 48 ROAD_CULVERT LINE 49 ROAD_DIVIDER LINE 50 ROAD_FOOTPATH LINE 51 ROAD_METAL LINE 52 ROAD_METAL_CENTER LINE 53 ROAD_UNMETAL LINE 54 ROAD_UNMETAL_CENTER LINE 55 ROCKAWASH LINE 56 RUNWAY LINE 57 RUNWAY_CENTER LINE 58 SAND LINE 59 STEPS LINE 60 STREAM LINE 61 UNSPECIFIED LINE 62 WALL LINE 63 BUILDING_HEIGHT POINT 64 FLAGPOLE POINT 65 FOUNTAIN POINT 66 IDGAH POINT 67 MANHOLE POINT 68 MOSQUE POINT 69 NAVIGATIONAL_LIGHT POINT 70 OHT POINT 71 PALMYRA POINT 72 POWERPOLE POINT 73 STATUE POINT 74 TOWER POINT 75 TREE_COCONUT POINT 76 TREE_OTHER POINT 77 WELL POINT 78 TXT_COCONUT TEXT 79 TXT_CULTIVATION TEXT 80 TXT_SAND TEXT 81 TXT_FEATURES TEXT 82 TXT_NAME TEXT

* BOUNDARY_ISLAND_AREA POLYGON * BUILDING_GROUP_ELEVATION POLYGON

Table 8 List of hardware and software established at Male, Maldives

SL. NO DESCRIPTION 1 ERDAS IMAGINE PROCESSING 2 ARC INFO BASE 9.0 3 AUTO DESK MAP 2004 4 LEICA PHOTOGRAMMETRY SOFTWARE(LPS) 5 LTO 2 Tape Data Cartridge 6 24 PORT 10/100/1000T GIGABIT AUTO SENSE ETHEMET SNMP MANAGEABLE SWITCH 7 STEREO VIEWING EQUIPMENT WTRELESS LIQUID CRYSTAL GLASSES, IR EMITTER FOR EACH WORK STATION 8 SERVER SYSTEM FOR REMOTE SENSING AND DIGITAL MAP DATABASE STORAGE AND DATA SERVING 9 WORKSTATION FOR REMOTE SENSING, GIS AND DIGITAL PHOTOGRAMMETRY OPERATIONS 10 LARGE FORMAT INKJET COLOUR NETWORK PLOTTER 11 HANDHELD GPS RECEIVERS List of figures

Fig. 1 Methodology for mapping at 1:25 000 scale using 1:40 000 scale aerial Photographs

Fig. 2 Methodology for mapping 16 select islands in 1:1 000 scale using 1:6 000 scale aerial photographs

Fig. 3 Seven Geographical Blocks for planning, managing and execution of the project

Fig. 4 NRSA’s SKA B-200 aircraft

Fig. 5 GPS Survey Pre Target

Fig. 6 Simultaneous observation of GPS reference / Pre-target Control point

Fig. 7 GPS Control Survey Deployment Plan

Fig. 8 Pre-target Control point imaged on aerial photograph

Fig. 9 Numbering schema for 1: 250 000 scale

Fig. 10 Numbering schema for 1: 50 000 scale

Fig. 11 Numbering schema for 1: 25 000 scale schema

Fig. 12 Aerial photography & Mapping of Maldives - timeline Fig. 1 Methodology for mapping at 1: 25 000 scale using 1: 40 000 scale aerial Photographs

RECONNAISANCE FOR PLANNING AERIAL SURVEY USING IRS-1D LISS-III DATA

FLIGHT PLANNING

AERIAL PHOTOGRA

GPS SURVEY PHOTOPROCES  REFERENCE SING STATIONS FOR AIRBORNE GPS

GPS DATA SCANNING OF PROCESSIN DIAPOSITI G VES  AIRBORNE

AEROTRIANGUL ATION & BLOCK ADJUSTME

ORTHOPHOTO

2D MAPPING

FIELD DATA

GIS HARD COPY GEODATAB MAPS Fig. 2 Methodology for mapping 16 select islands in 1:1 000 scale using 1:6 000 scale aerial photographs

RECONNAISANCE FOR PLANNING AERIAL SURVEY USING IRS-1D LISS-IV DATA

FLIGHT PLANNING

AERIAL PHOTOGRAPHY

GPS SURVEY PHOTOPROCESSING REFERENCE STATIONS FOR AIRBORNE GPS GCPs - POST POINTED

GPS DATA PROCESSING SCANNING OF AIRBORNE GPS DIAPOSITIVES GCPs

AEROTRIANGULATION & BLOCK ADJUSTMENT

3D MAPPING & CONTOURS

FIELD DATA

GIS GEODATABASE HARD COPY MAPS Fig. 3 : Seven Geographical Blocks for planning, managing and execution of the project Fig. 4. NRSA’s SKA B-200 aircraft Fig. 5 GPS Survey Pre Target Fig. 6 Simultaneous observation of GPS reference / Pre-target Control point Fig. 7 GPS Control Survey Deployment Plan Fig. 8 Pre-target Control point imaged on aerial photograph Fig. 9 Numbering schema for 1: 250 000 scale

Sheet Numbering for 1:250 000 scale 8N

43N01 43N09 43N17 43N25 43N33 43N41 7N

43N02 43N10 43N18 43N26 43N34 43N42 6N

43N03 43N11 43N19 43N27 43N35 43N43 5N

43N04 43N12 43N20 43N28 43N36 43N44 4N

43N05 43N13 43N21 43N29 43N37 43N45 3N

43N06 43N14 43N22 43N30 43N38 43N46 2N

43N07 43N15 43N23 43N31 43N39 43N47 1N

43N08 43N16 43N24 43N32 43N40 43N48 0 43M01 43M09 43M17 43M25 43M33 43M41 1S

43M02 43M10 43M18 43M26 43M34 43M42 2S

43M03 43M11 43M19 43M27 43M35 43M43 3S

43M04 43M12 43M20 43M28 43M36 43M44 4S 43M05 43M13 43M21 43M29 43M37 43M45 5S

43M06 43M14 43M22 43M30 43M38 43M46 6S

43M07 43M15 43M23 43M31 43M39 43M47 7S

43M08 43M16 43M24 43M32 43M40 43M48 8S 72 73 74 75 76 77 78 Fig. 10 Numbering schema for 1: 50 000 scale

Sheet numbering for 1:50 000 scale 0 15' 30' 45' 1deg 1deg 43N01A 43N01E 43N01I 43N01M

45’' 43N01B 43N01F 43N01J 43N01N

30’' 43N01C 43N01G 43N01K 43N01O

15’' 43N01D 43N01H 43N01L 43N01P

0 Sheets North of Equator

0 15' 30' 45' 1deg 0 43M01A 43M01E 43M01I 43M01M

15' 43M01B 43M01F 43M01J 43M01N

30' 43M01C 43M01G 43M01K 43M01O

45' 43M01D 43M01H 43M01L 43M01P

1deg Sheets South of Equator Fig. 11 Numbering schema for 1: 25 000 scale schema

Sheet numbering for 1:25 000 scale

0' 7'30" 15’0” 15'0”'

43N01A NW 43N01A NE

43N01A SW 43N01A SE

0' Sheets North of Equator

0' 7'30" 15’0” 0’'

43M01A NW 43M01A NE

43M01A SW 43M01A SE

15'0” Sheets South of Equator Fig. 12 Aerial photography & Mapping of Maldives - timeline