永久散射体雷达干涉技术监测上海地面沉降

Subsidence Monitoring in Shanghai Using the PSInSAR Technique

在地下水开采以及工程建设活动的双重影响下,城市地面沉降问题突出。传统的地面沉降监测水准测量虽精度高,但点密度低、成本较高。永久散射体雷达干涉技术(PSInSAR)监测地面沉降,具有低成本、大面积和高精度特点。选用2003～2005、2007～2008、2008～2009年间覆盖上海城区的中等分辨率Envisat ASAR影像,获得上海不同时期沉降速率图。其中2003～2005和2007～2008年间的结果与水准数据进行了比较验证,达到了毫米级精度。利用2008～2010年间获取的TerraSAR-X影像得到的沉降速率图还表明:基于序列高分辨率SAR数据不仅可以监测地面沉降,还可对大型单体建筑物及地铁等线状地物进行形变监测,证实了PSInSAR方法的有效性和应用潜力。

Land subsidence caused by over-exploitation of groundwater and high construction density is a global environmental problem. Traditional methods focus on ground-based monitoring, such as leveling measurements, which can offer high precision but are labor intensive and time consuming. The Permanent Scatterers Interferometry （PSInSAR） is an effective technique used to monitor surface deformation. The major advantages of this technique are that it provides high precision and large area coverage at low cost. In this investigation, we obtained subsidence velocity maps of Shanghai from Envisat ASAR datasets during 2003-2005, 2007-2008 and 2008-2009 respectively. The leveling data from ground measurements were used to validate the accuracy of the results using the PSInSAR technique. By comparing the leveling and subsidence velocity data from 2003 to 2005, and 2007 to 2008, it was possible to achieve measurement precision to the nearest millimeter. The results were then combined with TerraSAR-X images from 2008 to 2010 in Shanghai. This demonstrated that, in addition to monitoring subsistence, time series high resolution SAR data could also be used to monitor the deformation of large man-made structures. The case studies in Shanghai using both Envisat/ASAR and TerraSAR-X data gave results with accuracy to the nearest millimeter when detecting long-term subtle deformation. These results therefore illustrate the effectiveness and application potential of the PSInSAR technique.