Detection On Land Surface Deformation In Chongqing Area By D-InSAR

Chongqing city is located in the hilly region of south-eastern area of Sichuan Basin. It is in the upper reaches of the Yangtze River.Because the surface rock and soil is affected by a strong long-term weathering,geological disasters in this area is relatively frequent. The strength and stability of the rock and soil along the two sides of the river is also reduced because of the long-term erosion of Yangtze River. Controled by the fold structure,Chongqing area has a complex geological structure.The rock is serious-crushed, low-intensity and strong permeability. At the same time,the elevation difference of this area is relatively large. It is precisely because of these characteristics, making Chongqing become the country's four major geological disaster-prone areas.Synthetic aperture radar interferometry (InSAR) has been proposed as a potential earth observation technique, and it is an international research hot spot now. It has the advantages of all time and all weather operation, and cost-effective data acquisition for large areas. It uses the phase difference of the radar returns in two complex synthetic aperture radar images,of the same area acquired at separate viewpoints or times,to obtain the third dimension information of targets in the surface.As an active microwave imaging sensors, InSAR has high distance resolution and azimuth resolution,and also a characteristic of high automation.It has the advantages of all time and all weather operation, and cost-effective data acquisition for large areas.These features of InSAR technology make it more appropriate in geology, environment, oceans, disasters, mapping applications and many other fields, especially for the areas which are difficult for traditional optical sensors. All in all, InSAR has a special significance for remote sensing.Using InSAR technology to the extract the surface deformation of Chongqing area is feasible.It can provide a scientific basis for the study of geological disasters.And has important significance in both science and practice field. This dissertation introduced the principle and method of D-InSAR for surface displacement measurememt,analyed the procedure and mathematic model of InSAR. Also,the dissertation introduced the registration of InSAR complex images and the main algorithm of phase unwrapping.At the same time, the radar data processing software DORIS based on Linux operating is profoundly studied.The algorithms of DORIS, as well as its steps, are comprehensively mastered.Choose three ERS-1/2 satellite SAR images covering the southern area of Chongqing to got the surface deformation,based on three-pass differential InSAR method.We used the radar image in July 27,1998,orbits 17085 as the master image,the other two images as slave images,to get the topographic information and the deformation information respectively.First of all, the simulation precision orbit data is calculated according to the position data of the satellite orbit. The coarse offsets were calculated. The window-based automatic registration technique is used,also the correlation coefficient method. These are all for the coarse registration. And then the precise offset parameters of the two radar images are obtained for precise registration.After precise registration,a sub-pixel matching accuracy is reached. Filtering is also necessary in both azimuth and range direction.The Interferogram is producted by multiplied the two images in complex conjugation. After that,in order to got the real surface elevation information, flat-earth effect must be removed. Then the phase unwrapping is processed. After unwrapping the interferogram of the topography, process it with the wrapped deformation interferogram and got the the differential interferogram. of surface deformation during the period 1996-1998 of chongqing region.Finally, multi-temporal Landsat TM and ETM+ data are used to compare and analyze the differential interferometric result.Interference fringes are obvious only in the urban area of Chongqing, the northern part of Nanchuan County, PuiLing County and Jiangbei County.The coherence is very low in other areas of the interferogram. Only the noise can be seen.After Geo-coding and projection transformation,the 4 areas with obvious fringes were found in the TM/ETM+ images respectively. Compared the differential interferogram with the TM/ETM+ images in 1988 and 2001 of these 4 areas, the reasons for surface deformation were analyzed.