The LiDAR point clouds obtained from the LiDAR data acquisition missions are preprocessed by the Data Processing Component (DPC) of Phil-LiDAR 1 using TerraScan. During preprocessing LiDAR point clouds are classified into ground, buildings, vegetation, etc. Four types of LiDAR point clouds are produced in ASCII format namely: d_ascii, s_ascii, t_ascii, and v_ascii. These files generate the last-return digital surface model (DSM), the first-return DSM, secondary digital terrain model (DTM) and the DTM using ArcMap, respectively. One ASCII file corresponds to a 1 km by 1 km tile. These files were sent to the SUCs/HEIs for further processing.

Figure 2.6 Schematic representation of the ASCII files from TerraScan and the digital elevation models generated.

Figure 2.6 Schematic representation of the ASCII files from TerraScan and the digital elevation models generated.

 

       In addition to the ASCII files, TerraScan also produces dxf files of the LiDAR point cloud. Dxf is a file extension of a graphic file format used in computer assisted drafting (CAD) softwares, e.g. AutoCAD. Dxf stands for drawing exchange format. It is introduced to enable interoperability between AutoCAD and other CAD and related programs like TerraScan. The dxf file has four component data files: the line, point, polygon, and annotation. In the editing process, the polygon and the annotation files are converted into shapefiles. The dxf file of Mananga is shown in Figure 2.7.