Mathematical Morphology Land Subsidence In The Study

Land subsidence is one of urban geological disasters in some metropolitan area, where groundwater is the main water supply source. Due to the continuous years of drought and the long-time over-exploitation of groundwater in emergency water sources, the groundwater flow field and the groundwater level have been changed in Beijing to cause the land subsidence. Persistent Scatterers for SAR Interferometry (PS-InSAR) is used to monitor land subsidence to obtain the deformation information. But how to automatically, semi-automatically extract the specific features from the deformation information, the suitable image analysis technique must be selected.Based on the spatial analysis function of GIS, the features are extracted by the theory and method of mathematical morphology, and the spatial distribution of land subsidence is analyzed under the influence of groundwater level. This paper attempts to analyze land subsidence by the theory and method of mathematical morphology. The main work is presented as following:Firstly, the amount of land subsidence from 2004 to 2005 is chose as a data source, which is obtained by the PS-InSAR technology. The 5×5 disk-shaped structuring element is selected to carry out the morphological enhancement to this image. Then using the morphological reconstruction method and the marker-controlled watershed segmentation, the subsidence funnels are extracted and analyzed.Secondly, it presents the spatial and temporal variation of the mainly influence factors (the groundwater level, the Quaternary strata thickness), and with which the spatial relations between land subsidence. Based on the morphological reconstruction and the marker-controlled watershed segmentation, the features such as the groundwater cones of depression and the more thickness cones of Quaternary deposits are derived. These features are then applied to do spatial overlay analysis with the subsidence funnels.Finally, using the mathematical morphology, the spatial distribution of land subsidence is analyzed under the influence of groundwater level. The different changes in groundwater levels are given the different dilated coefficients, with which to change the original morphological convolution template coefficients. Then using this dynamic convolution template affected by the groundwater level, the accumulated settlement is dilated to obtain the distribution of land subsidence.The paper shows that the target features are effectively extracted and the spatial distribution of land subsidence is analyzed under the influence of groundwater level by the methods of mathematical morphology. The new method is provided for the analysis and study of land subsidence. So it enriches the application field of mathematical morphology.