Research Of Coherent Target Interferometry And Its Applications To Surface Subsidence Fields

At present there are about 50 cities in 16 provinces suffered from subsidence, and the economic losses are more than 100 million each year, which have become one of the limiting factors of the urban sustainable development. In order to know the status of subsidence in time, forecast the trends of subsidence exactly and make the prevent policy, the efficient way to monitor subsidence must be carried out. On the other hand, with the development of the technique of spaceborne earth observation (EO), specially the development of the Diffferential SAR Interferometry in last century, it is possible to get the information of the topography and deformation of the earth surface with high resolution independent of the weather and sun illumilation. Despite of the tremendous potential of DInSAR technique, limitations due to temporal decorrelation, spatial decorrelation and atmospheric dishomogeneities prevent this technique from wildly being applied in crustal deformation monitoring, especially in the low-rate deformation cases.In this paper based on the analysis of traditional DInSAR, the CT-DInSAR research is carried out to meet the need of the deformation monitoring on long time scale. The coherent targets are selected from the time scale as the research object. By using linear deformation model, the phase of the selected pixels is analyzed to obtain the result of deformation. In the end, the algorithm proposed in this paper is applied to Suzhou and Cangzhou citys, which are in Jiangsu and Heibei provinces respectively. And the results of deforamation of 8 years are presented and are compared with the leveling measurements showing a good agreement.In this paper, we focus on the following points:1. The selection of the Coherent Target (CT) As the objects we study on the long time scale, the accuracy of the selection effects the result of this algorithm directly. Based on the analysis of the spatial and temporal statistical characteristics of the coherent targets, the difference of selection method between temporal Dispersion Index of amplitude on time and the correlation threshold is presented. For a stack with sufficient images, the method of Dispersion Index of amplitude can get the CTs with the origin resolution, and for a small number of images set, the correlation threshold is adopted instead of the Dispersion Index of amplitude, which promises the accuracy at the cost of the resolution, because the estimation of the statistic characteristic of amplitude is not good on the condition of the limited number of images.