Preprocessing includes POS calculating, laser processing and coordinate transforming. The POS calculating produces PosT file which can output carrier's location and attitude information. The laser processing step decodes raw data and operates coordinate transforming, and as a consequence, LAS point cloud in WGS-84 coordinate system is produced. Coordinate transforming is based on requirements from User, and this step transforms point cloud result into an independent coordinate system of the project.
● Point Cloud Post-processing
Point cloud post-processing includes vacuation of laser point cloud, excluding of noisy point as well as filtering and classification. After elaborate classification of the laser data, precise ground points without vegetation point, noisy point and construction point will be produced, and then, elevation points remain terrain features can be extracted.
● Topographic Mapping
This process includes the generation of elevation point and contour line, as well as the drawing of surface features. Contour lines are generated based on ground points. Then, after modification, DEM products with high accuracy can be generated. After that, input point cloud into CAD software and draw relevant surface objects depend on the environment of the survey area. And at the end of the procession, we can get the 1:2000 strip tropospheric map as the final result.