Laser scanning technologies are widely used to solve civil engineering problems and land use management in a GIS environment including digital terrain models (DTMs) creation. Some gaps in raw laser scanning data processing algorithms for DTM are analyzed. Algorithms for filtration, triangulation, and defragmentation are proposed. Advantages and disadvantages of the algorithms proposed are discussed. Triangulation algorithm can serve to defragment cloud of laser scanning points into semantic component parts. Defragmentation includes recognition of engineering objects and other objects of the terrain and their delineation. Results of applications to real problems show the robustness of algorithms proposed.