Interferometric Synthetic Aperture Radar and Radargrammetry for Accurate Digital Elevation Model Generation in New South Wales, Australia By Jung Hum Yu A thesis submitted to The University of New South Wales in partial fulfilment of the requirements for the degree of Doctor of Philosophy Geodesy and Earth Observing Systems Group School of Surveying and Spatial Information Systems The University of New South Wales Sydney NSW 2052, Australia March, 2011 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 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 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 ABSTRACT A topographic map is a prerequisite to the thematic map of geological and environmental information. The Digital Elevation Model (DEM) has become an important source of topographical information for many scientific and engineering uses, such as hydrological and geological studies, infrastructure planning and environmental applications. Digital Elevation Models (DEMs) can be generated by using various techniques and by using a range of data sources, including ground surveying, photogrammetry, optical remote sensing, radar, and laser scanning. Where topographical data is unavailable, global coverage elevation data sets, typically DEMs based on remotely sensed data, can be the main source of information. Remote sensing techniques are a rapid means of acquiring elevation information over extensive terrain. In particular, processing remotely sensed data collected by Earth observation satellites is a very efficient and cost-effective mean of acquiring up-to-date and relatively accurate land cover and topographic information. Active remote sensing sensors (such as radar), which can operate in almost all weather conditions and also in darkness using their own illumination have become an important remote sensing technique. In radar remote sensing systems, DEM generation methods are based on the analysis of Synthetic Aperture Radar (SAR) images, and include interferometry, radargrammetry, radarclinometry, and polarimetry. The two most common methods for generating DEMs from SAR images are: (1) radargrammetry, a technique derived from i photogrammetry and based on the stereoscopic principle, (2) interferometry, based on the phase differences between identical imaged points in two SAR images. This thesis describes the methods or techniques of DEM quality improvement and reduction in elevation errors, which are generated by various SAR techniques and imagery. InSAR DEM generation relies on the measurement of phase difference between two sets of complex radar signals, i.e. the range difference between the satellite-borne radar instrument and the ground targets reflecting the radar transmissions. In InSAR DEM generation, the so-called “master image” parameters, such as signal wavelength, incidence angle, and SAR image relationship (i.e. perpendicular baseline), affect the final DEM products. Furthermore, the different orbit direction (ascending and descending) provides a different representation of terrain and multi-temporal observation, leading to a more detailed representation of terrain over the same target area. Hence, ways of improving the quality of InSAR DEMs include using images collected by the satellite sensor from different orbit directions and multi-epoch data acquisitions. Also, in the case of InSAR DEM generation, major issues related to long satellite repeat-cycle times and low resolution DEM updating are discussed and solutions are proposed for ground distortion excluding method and selective elevation updating. Depending on the data acquisition conditions, the InSAR technique is less robust and more difficult to implement, particularly because the InSAR technique often produces poor results caused by poor coherence, atmospheric differences between two ii processed images and conditions. These three factors are influenced by the incidence angle and the Doppler similarity, which are quite stringent. InSAR requires the expectations of a certain baseline while interferometry is sensitive to the direction of sensor movements and some other factors. For this reason, the radargrammetry technique is an important alternative for DEM generation. In summary, the major contributions of this thesis are to analyse research into the following; • Wide coverage and weather independent elevation data generation method using active remote sensing • Stable data updating of various ground information by different capability satellite remote sensing • Geometric distortion exclusion in side-looking observation systems • Elevation accuracy improvement by atmospheric disturbance reduction • Robust DEM generation techniques using InSAR and radargrammetry iii ACKNOWLEDGEMENT This research was performed in the Geodesy and Earth Observing Systems (GEOS) group in the School of Surveying and Spatial Information Systems (SSIS) at the University of New South Wales (UNSW), Sydney, New South Wales, Australia. Many people supported me in various ways during the journey of my research. First and foremost, I would like to thank my supervisor, Associate Professor Linlin Ge, for supervising and supporting my doctoral research. I would also like to express my thanks to my co-supervisor Chris Rizos, Professor and Head of SSIS at UNSW, for his patience and inspiration on supporting my research. I would not have learned and achieved so much without the support and encouragement from my supervisors. I would also like to thank both of my supervisors again for their careful reading of this work. Thanks also go to all the people at the SSIS for numerous discussions, particularly relating to remote sensing and the philosophy of life. Especially, I am so grateful to our current and former GEOS group members, including Dr. Xiaojing Li, Dr. Hsing-Chung Chang, Alex Hay-Man Ng, Kui Zhang, Wendi Peng, Wing Yip Lau, Dan Meng, Zhe Hu, Li Gou, Hai Tung Chu, Rattanasuda Cholathat, Wang Xin, Yuanyuan Zhang. I would like to also acknowledge Dr. Sungheuk Jung, Dr. Yusen Dong, Dr. Mahmoud Salah, Mr. Cemal Ozer Yigit, visiting scientists at UNSW from Chungbuk National University in Republic of Korea, China University of Geosciences in China, Banha University in Egypt, Selcuk University in Turkey. iv The European Space Agency is acknowledged for providing data from the ERS SAR missions. The Earth Remote Sensing Data Analysis Centre is acknowledged for providing the ALOS PALSAR data. The Land and Property management Authority is acknowledged for providing the LiDAR data. I would like to also acknowledge Korea-Australasia Research Centre members; Prof. Chung-Sok Suh, Dr. Gi-Hyun Shin, Dr. Seung-Ho Kwon, Dr. Sungbae Ko, Ms. Hyunok Ke, Mr. Joseph Kim. And, my friends Mr. Daehui Oh and his wife Ms. Jungeun Kim, Dr. In Jun and Ms. Mie Yang, and Mr. Chaelqu Yang, also my colleagues Ms. Jasmin Kim, Mr. Hongju Park. Last, but far from least, I give my most heart-felt appreciation and thank my parents, my sister, brother-in-low and nephew for their emotional supports and understanding during my PhD studies. v LIST OF ABBREVIATIONS ACRES Australian Centre for Remote Sensing ALOS Advanced Land Observing Satellite ALS Airborne Laser Scanning AMI Active Microwave Imager CCRS Canada Centre for Remote Sensing COSMO-SkyMed Constellation of small Satellites for the Mediterranean basin Observation CRCSI Cooperative Research Centre for Spatial Information CSA Canadian Space Agency DEM Digital Elevation Model DInSAR Differential Interferometric Synthetic Aperture Radar DLR Deutsches Zentrum für Luft- und Raumfahrt (German Aerospace Centre) EORC Earth Observation Research Centre ESA European Space Agency ENVISAT Environmental SATellite ERS-1/2 1st/2nd