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With the development of network and information technology, it is highly desirable to create 3D geoscience applications in the network environment. However, construction of web-based 3D terrain model is one of the foundation works of 3D geoscience applications in the network environment. This paper presents a new method of constructing large-scale 3D terrain model based on Extensible 3D (X3D). In this way, we first use Geospatial components of X3D to build 3D terrain model by using DEM as the data source, then we publish the 3D terrain model to the internet with a architecture of Brower/Server and plug-in technology. To promote the display performance of large-scale 3D terrain model, We presents an approach that using the Level of Detail (LOD) technology to simplify the 3D terrain model. The application results show that the method this paper presented has advantage of easy to integrate with other network system, thereby easy to realize data sharing and interoperation; the method also has virtues of fast display speed, high ability of interaction. It’s an effective method for constructing large-scale 3D terrain model in network environment.

Land subsidence in urban area is becoming a severe geological hazard disturbing the urban construction and development. Persistent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR) technique has demonstrated a good capability of monitoring the large scale land deformation. High resolution and short wave radar data can help to improve the precision of deformation detection based on PSInSAR. In this paper, 15 scenes of TerraSAR-X SAR data are used to derive the estimation of the subsidence rate in the Wuqing district, Tianjin city in China. The combination of TIN and nearest-connection method (NCM) are first used to establish the differential network model. The results show that high resolution TX image can dramatically increase the valid PSs and improve investigation reliability, especially in linear man-made constructs.