Spaceborne Interferometric Synthetic Aperture Radar And Its Application On The Glacial Geomorphology In The Antarctic

It is difficult to reach the Antarctic continent since it is covered by ice and snow, with cold weather, surrounded by the ocean and far away from the other continents. Till the fifties of the twentieth century, the outline of the Antarctic was presented in the world map. However, the more curious world is the one in the outline. With the progress of the science and technology, especially for the development of the earth observation from space, Antarctica appears before us more and more perfectly. In 1997, the Canadian Radarsat-1 satellite was rotated in orbit. With its synthetic aperture radar (SAR) antenna looking south towards Antarctica, it permitted the first high-resolution mapping of the entire continent of Antarctica.The Antarctic is in very close relationship with the global climate, ecology environment, and the future of the human being. It is impossible to explore the Antarctic without any touch. While, 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 Antarctic profoundly, and open a new situation for us to explore the ice cap, the continent, and 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 advantage of all time, all weather operation and cost-effective data acquisition for large area. So it can be utilized for digital elevation model (DEM) generation, topographic mapping in large areas, especially those areas that are more inaccessible, even in polar night. Moreover, it can detect the surface change in cm even mm level, and can be adopted to monitor the change and movement of ice cap, ice shelf and glaciers, to obtain the dynamic change of the whole Antarctic, which provide the information and clue for the relation of the polar area and the global.The main research motive exists in two aspects: one is to support the Chinese national polar research expedition, to provide new technology and explore new way; the second is to contribute to the polar environment research. During the 16^th Chinese National Antarctic Research Expedition (CHINARE) 1999/2000, a field survey of Grove Mountains core area was completed with GPS and total station in one month by two geodetic surveyors. However, in Antarctica, 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, combining with Chinese National Antarctic ResearchExpedition, InSAR technology should be studied carefully; and on the other hand, it should be applied to the Antarctic research more and more perfectly. The main contents of the thesis are:(1) Digital Elevation Model generation of Grove Mountains with InSAROn the premise of comprehensive analysis of contour tendency, glacier movement, glacier geomorphology, and the correct height reference point, the Digital Elevation Model (DEM) of Grove Mountains, east Antarctica is obtained successfully with InSAR. Based on the comparison of InSAR DEM and the field survey data, it is demonstrated that the InSAR DEM is in high accuracy and confirmed that InSAR can be utilized in Antarctic topographic mapping. 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.(2) The filtering of InSAR-DEMConsidering the need of map and contour making in the future, the ways to filter InSAR-DEM have been investigated. By comparing and analyzing the mean filter, median filter and binomial coefficient filter, the binomial coefficient filter is demonstrated as a simple and feasible method without phase distortion of signal.(3) Using external DEM in InSAR DEM generation and differential InSARThe essential, similarities and differences of using external DEM in InSAR DEM generation and differential InSAR are analyzed in detail. Meanwhile, the benefit of external DEM in InSAR DEM generation is demonstrated, which 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. Based on the SAR image pairs in the study, the small baseline in InSAR DEM generation is analyzed that it is very sensitive to error. Therefore, it is very important to follow the optimum baseline principle.(4) Ground subsidence detected by differential InSARThe precision of the external DEM used in differential InSAR is pointed out and proved in theory, which is correlated to spatial baseline and the deformation value. The subsidence of the mining area is detected by 2-pass D-InSAR with the external DEM with 1 arc second resolution. It is further confirmed that differential InSAR is a very efficient means to monitor the subsidence, and it provides the information of the whole plane not only point and line, while traditional methods can't do and realize.(5) Analysis of the best Antarctic RAMP/DEM at presentThe comparison and analysis of RAMP/DEM and the field survey data in Antarctic area shows that the precision of RAMP/DEM can't meet the need of small-scale deformation. At present 3-pass and 4-pass are the main methods in differential InSAR application. If the high precision external DEM is available, 2-pass D-InSAR method is feasible.(6) Blue ice distribution, ice flow line and crevasses interpretation based on coherence map Based on the coherence map, blue ice distribution is extracted successfully and the relationship of blue ice and meteorite is discussed. Meanwhile, the ice flow line in the coherence map helps to analyze the glacier movement, which provides important information and reference to compare the InSAR-DEM and GPS-DEM. In addition, the crevasse interpretation is to guarantee the safety of field expedition.(7) The influence of satellite attitude to coherence in interferometrySAR image data are the basis for InSAR research. According to the low coherence of SAR image pairs since year 2000, the gyro exception of ERS-2 is presented. The quality analysis of SAR interferometry image based on coherence is brought forward. The analysis of Doppler centroid frequency difference induced by satellite attitude provides new reference for user to choose the ERS-2 data for interferometric application.