In this paper, the new method is proposed for filtering of airborne LiDAR data based on improved Triangulated Irregular Network(TIN) algorithm and the details of filter principle is described. Firstly, LiDAR point cloud data is organized and designed by regular grid and TIN, the seed points from point cloud data are selected by regional sub-block method or mathematical morphology. Then, an initial sparse TIN is created from the seed points and densified upward gradually and the ground points are extracted through an interactive process. In experiments it is shown that this filtering method can effectively remove different sizes of buildings, low vegetation and other objects, and keep topographical features better.

Groundwater overdraft in Xi'an City is the main cause of the subsidence since 1959. In recent years, ground fissure has been one of the most serious geological hazards in Xi'an, China. This paper aims to research the application of high-precision 3D terrestrial laser scanning techniques (TLS) in land subsidence and ground fissure monitoring. The paper use TLS scanning to monitor a typical ground fissure in the southern suburb of Xi'an. Large-scale subsidence is obtained by processing and comprehensive analysis these fissure data, on the other hand, the paper investigate the characteristics of spatio-temporal evolution between the land subsidence and ground fissure. Finally, compared with Global Positioning System (GPS) measurement in the same period, TLS scanning result in tested area is reliable. The research shows that there is obvious spatio-temporal correlation between land subsidence and ground fissure distribution.