Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1998 Improved geodetic control by GPS for establishing a Geographic Information System for Sri Lanka S. D. Sarathchandra Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Applied Mathematics Commons, Civil Engineering Commons, Earth Sciences Commons, and the Geography Commons Recommended Citation Sarathchandra, S. D., "Improved geodetic control by GPS for establishing a Geographic Information System for Sri Lanka " (1998). Retrospective Theses and Dissertations. 11889. https://lib.dr.iastate.edu/rtd/11889 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. 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Sarathchandra A dissertation submitted to the graduate faculty in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Major: Civil Engineering (Geometronics) Major Professor: K. Jeyapalan Iowa State University Ames, Iowa 1998 Copyright © S. D. Sarathchandra, 1998. All rights reserved. UMI Ntusber: 9841084 UMI Microform 9841084 Copyright 1998, by UMI Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. UMI 300 North Zeeb Road Ann Arbor, Ml 48103 II Graduate College Iowa State University Tliis is to certify tliat the Doctoral dissertation of S. D. Sarathchandra has met the dissertation rec[uirements of Iowa State University Signature was redacted for privacy. Commictee \j Signature was redacted for privacy. Committee Member Signature was redacted for privacy. Committee Member Signature was redacted for privacy. Commmfe Member Signature was redacted for privacy. 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Ill TABLE OF CONTENTS 1 INTRODUCTION 1 1.1 Research objectives 3 1.2 Present available accuracy of the network 4 1.3 GPS data collection procedure for a new adjustment 5 1.4 Transformation parameters 5 1.5 Spatial data for the cadastral map layer 6 1.6 Improving digitized coordinates by a sequential adjustment 7 2 CONCEPTS OF A GIS AND THE SRI LANKAN GIS 9 2.1 Components of a GIS data base 9 2.2 The Sri Lankan GIS 10 3 EXISTING GEODETIC CONTROL OF SRI LANKA 12 3.1 History 12 3.2 Need for a re-adjustment 13 3.3 Means of evaluating weaknesses of the network 14 3.3.1 Old observations 14 3.3.2 Comparison of distances 16 3.3.3 Evaluation of the old adjustment methodology 18 3.3.4 Effect of the Geoid and the Ellipsoid 20 3.4 The present accuracy of the network 21 iv 4 PRINCIPLES AND APPLICATIONS OF GPS 24 4.1 Components of GPS 25 4.2 Orbital motion of a satellite 27 4.3 GPS satellite transmissions 29 4.4 Positioning methods 29 4.4.1 Stand along mode 30 4.4.2 Relative mode (differential GPS) 31 4.4.3 Kinematic and static modes 31 4.5 Computations in differential GPS 33 4.6 Errors effecting GPS positioning 36 4.7 Specifications of differentiiil GPS 38 4.8 Getting GPS data in to a GIS 39 5 A NEW GEODETIC CONTROL SYSTEM 41 5.1 Reconnaissance 41 5.1.1 Field measurements used for old networks 43 5.2 Geodetic control and its users 44 5.3 GPS observations for new adjustment 44 5.3.1 Expected and predicted accuracy of the network 45 5.3.2 Simulated data 47 5.3.3 Fixed stations for the adjustment 49 5.3.4 Procedure for GPS observation to achieve the required positional accuracy of the network 50 5.3.5 Pre-adjustment using simulated data 52 5.3.6 Observation and processing of actual GPS data 52 5.4 Gravity me3isurements 57 5.5 Azimuth observations 58 V 5.6 Mathematical surface for the geodetic network 59 5.7 Everest vs. GRS80 for Sri Lanka 61 5.7.1 Everest ellipsoid 61 5.7.2 GRS80 ellipsoid 62 5.8 Reduction of angle and distance observations 63 5.9 The least squares adjustment 64 5.10 Approximate values of parameters for the new adjustment 65 5.11 Weights axid priori variance 66 5.12 Observation equations 67 5.12.1 Directions 67 5.12.2 Distances 68 5.13 Solution for parameters 68 5.14 Evaluation of the adjustment 71 5.14.1 Using GPS observations for evaluation 71 5.14.2 Vaxiance-covEuriance matrices for parameters and adjusted obser­ vations 72 6 TRANSFORMATION PARAMETERS FOR THE NEW ADJUST­ MENT 74 6.1 Mathematical models for coordinate trajisformations 76 6.2 Methods used for the coordinate transformation from NAD27 to NAD83 78 6.3 Accuracy of coordinate transformation of Sri Lanka 80 6.4 Two dimensional coordinates 81 6.4.1 Projection Surfaces and their classifications 84 6.4.2 Map projection for Sri Lanka 86 6.4.3 Normal Cylindrical Projections 87 6.4.4 Transverse Mercator Projection 89 vi 7 GETTING SPATIAL DATA INTO THE GIS 92 7.1 Data layers for cadastral and engineering applications 93 7.1.1 Scanning large scale cadastral maps 94 7.1.2 Major problems faced in scanning and vectorization of cadastral maps 95 7.1.3 Improving digitized coordinates using a least squares sequential adjustment 96 7.2 Spatial data sources for data analysis in the Sri Lankan GIS 98 7.2.1 1 : 500,000 scale road map 100 7.2.2 1 ; 100,000 scale Land use map 101 7.2.3 1 ; 50,000 Topographic map 102 7.2.4 1 : 10,000 Topographic map 103 8 CONCLUSION 104 8.1 New geodetic network 105 8.1.1 GPS data for the geodetic network 105 8.1.2 Reference ellipsoid for Sri Lanka 106 8.2 Coordinate transformation 107 8.3 Spatial data for cadastral and engineering applications 107 8.3.1 Updating coordinates by a sequential adjustment 108 8.4 Spatial data from small scale maps 108 8.5 Summary of recommendations 109 APPENDIX A EXISTING GEODETIC CONTROL Ill APPENDIX B PROPOSED LAND INFORMATION NETWORK FOR SRI LANKA 119 APPENDIX C RESULTS OBTAINED FOR A NEW ADJUSTMENT USING OLD OBSERVATIONS 120 vn APPENDIX D ''Con.cord" MAIN MENU 128 APPENDIX E INPUT FILE FOR A GEOLAB ADJUSTMENT WITH NEW GPS OBSERVATIONS 129 APPENDIX F A PART OF THE OUTPUT FILE FOR AN ADJUST­ MENT WITH NEW GPS OBSERVATIONS 142 APPENDIX G RESULTS OF SCANNING AND VECTORIZATION OF CADASTRAL MAPS 158 APPENDIX H PART OF A SRI LANKAN CADASTRAL MAP . 166 APPENDIX I GEO-REFERENCING ERRORS DUE TO MOUN­ TAIN PEAKS IN 1 : 500,000 MAP 167 APPENDIX J SUBROUTINES USED FOR ''Concord" AND THE SEQUENTIAL LEAST SQUARES ADJUSTMENT 168 REFERENCES 182 vm ACKNOWLEDGMENTS I would like to take this opportunity to thank my major professor, Dr. K Jeya- palan for his advice and encouragement in conducting this research and for his guidance throughout my graduate studies at the Iowa State University. I would also like to thank Dr. Dah-Yinn Lee, Dr. John M. Pitt, Dr. Mushtaqur Rahman and Dr. Sunday U. Tim for serving in my program of study committee and reviewing my dissertation. My thanks go to Dr. Say K. Ong and Dr. Thomas S. Colvin for reviewing my dissertation and serving as committee members for my final examination. I extend special thanks to the Surveyor General of Sri Lanka for approving leave for my higher studies. Fi­ nally, I thank my wife Ajantha and two sons Vajira and Thusara for their patience and understanding. 1 1 INTRODUCTION Sri Lanka is in the process of establishing a Geographic Information System (GIS). A GIS is a combination of spatial data which provides the relative location of points, lines or areas on the earth surface and attribute data related to these individual points, lines and polygons (Burrough, 1986). Many base map layers, such as land use, elevation, soil type, transportation and cadastral layer showing property boundaries should be included in the GIS.