Land subsidence monitoring by D-InSAR technique

Nowadays, the researches of using Differential Interferometric Synthetic Aperture Radar (D-InSAR) tech- nique to monitor the land subsidence are mainly on how to qualitatively analyze the subsidence areas and values, but the analysis of subsidence process and mechanism are insufficient. In order to resolve these problems, 6 scenes of ERS1/2 images captured during 1995 and 2000 in a certain place of Jiangsu province were selected to obtain the subsidence and velocities in three time segments by ''two-pass'' D- InSAR method. Then the relationships among distributions of pumping wells, exploitation quantity of groundwater, and confined water levels were studied and the subsidence mechanism was systematically analyzed. The results show that using D-InSAR technique to monitor the deformation of large area can obtain high accuracies, the disadvantages of classical observation methods can be remedied and there is a linear relationship among the velocities of land subsidence, the water level and the exploitation quantity.

Research on Spatio-Temporal Differentiation Characteristics of the Construction Level of Green and Plaza Land in China

Green and plaza land(GPL)is one of the basic elements of urban construction,and is also the most basic public space to meet the needs of citizens for a better life.The exploration on its internal development laws can provide theoretical foundations for the planning of GPL and creating good human settlements.Taking 612 cities in China as the study area and from the"people-land"perspective,this paper selects the total GPL area,the per capita GPL area,and the land use proportion of per capita GPL as indicators to analyze the spatio-temporal differentiation characteristics and evolution rules of the construction level of GPL in China from 1996 to 2016,by using mathematical statistics and spatial analysis methods.The result shows:(1)from a national perspective,the construction level of GPL in China has been rapidly improved along with the temporal evolution,but there is still a big gap from the upper limit of the standard.In terms of the spatial distribution,regional differences have always been great,and the cities scoring below the standard are concentrated in the eastern and central regions,while high-scoring cities are more concentrated in the western region;the distribution of the land use proportion of per capita GPL is in a pattern that the eastern region has the highest proportion,followed by the western region,central region,and northeastern region successively.(2)From the perspective of scale,differences between cities of different sizes exist over a long period of time,and there is an obvious imbalance in the per capita GPL area as well as the land use proportion of per capita GPL between different cities.The construction level shows that small cities have the highest level,followed by medium-sized cities and then large cities.