A Study On InSAR DEM Acquisition, Precision Analysis And Structural Relief Obtainment

Tibetan Plateau, with an average elevation of over 4500 meters, is located in the southwest of China. The plateau is surrounded by mountains, with Tarim Basin in north and Indo-Gangetic Plain in south, so it is also called the Ridge of the World. Tibeten Plateau is one of the youngest tectonic activitive areas in the world, of particular geological structures. It is also a strong tectonic activitive area, with a lot of active faults and surface ruptures. The different characters, dimensions, active ranges, deep-seated structures, and formational and evolutional histories, are worth our exploration and acqierement.Tibetan Plateau is in very close relationship with the global climate, ecology environment and the future of the human being. It is impossible to explore the Tibetan Plateau without any field measurement. However, it is unscientific to reveal its mysteries foot by foot. The technologies of the earth observation from space provide us more approaches to understand the Tibetan Plateau profoundly, and open a new situation for us to detect its mechanism.Synthetic aperture radar interferometry (InSAR) has been proposed as a potential earth observation technique, and it is an international research hotspot now. It has the advantages of all time and all weather operation, and cost-effective data acquisition for large areas. So it can be utilized for digital elevation model (DEM) generation, topographic mapping in large areas, especially those areas that are inaccessible. Moreover, D-lnSAR can get the co-seismic fields, and PS-lnSAR can detect the surface changes in cm even mm level, and can be adopted to monitor the changes and movements of active faults, to obtain the dynamic changes of the whole Plateau, which provide the information and clue for the relationship of the plateau area and the globe.The main research motive is to support the Tibetan research expedition, to provide new technology and explore new ways. Traditional mapping methods are no longer the most efficient means of obtaining topographical maps or DEM in large areas especially in inaccessible or difficult environments. Therefore, InSAR technology should be studied carefully, and on the other hand, it should be applied to the Tibetan Plateau research more and more perfectly.The main contents of the thesis are:(1) Digital Elevation Model generation of Damxung-Yangbajain, Tibet with InSAR On the premise of comprehensive analysis of SRTM and 1:50000 DEM, the Digital Elevation Model (DEM) of Damxung-Yangbajain, Tibet is obtained successfully with ERS-1/2 tandem data. Based on the comparison of InSAR DEM and the 1:50000 DEM, it is demonstrated that the InSAR DEM is in high accuracy and confirmed that InSAR can be utilized in Tibet topographic mapping.(2) Influential factor analysis of height measurement by InSAREspecially based on the SAR image pairs in the study, the small baseline in InSAR DEM generation is analyzed that it is very sensitive to errors. Therefore, it is very important to follow the optimum baseline principle. Meanwhile, the results reveal that the influence of ground gradient to interferometric phase can't be neglected. If the height changes quickly, it results in interferogram overlap and severe decorelation, and the height can't be calculated correctly.(3) Using external DEM in InSAR DEM generationThe essential of using external DEM in InSAR DEM generation, as well as the similarities and differences of using external DEM in differential InSAR is analyzed in detail. Meanwhile, the benefit of external DEM in InSAR DEM generation is demonstrated, which provides the referenced coordinate and makes the phase unwrapping much easier especially for the steep slope, and the profiles that deviate from the ground truth are corrected to be consistent with the truth.(4) Primary applied study of PS-lnSARBased on the analysis of the permanent scatter points, the result can be achieved, that points in the south of the basin subside, while points in the north rise. The maximal sedimentation rate is 6mm per year, while the maximal ascending rate is 7mm per year.(5) Execution of special mapsSlope, aspect, shade and 3D maps are made by ETM+ images, InSAR-DEM and SRTM. Tectonic physiognomy of the study area is identified.