Mapping of forested areas and water bodies was very limited in the past. Access to such areas with traditional survey techniques (total station, GNSS etc.), analogue/digital photogrammetry or radar technologies was very limited because of the dense and multilayer vegetation, very complex topography, swamps, narrow beach and steep cliffs, deep water, etc. Gathered data by survey or remote sensing, were used for generation of digital terrain models (DTM, sometimes with unknown accuracy. Implementation of airborne laser scanning technology (ALS; LiDAR - Light Detection and Ranging) to monitor complex environments which are very hard to see by human eye or other instruments in 3D space - opens new opportunities to identify precisely the vertical and horizontal structures, objects and magnitudes. Use of precision DTM based on ALS point clouds, is now a widely deployed method in many environmental applications including: morphometry analyses, landslide monitoring, geomorphological and hydrological modelling etc. Dense forest crown cover and undergrowth is limiting the penetration of laser beams but now the ground (DTM) can be “seen” very detailed if using high density of ALS data performed with narrow nadir-off angle and using full waveform as well. The bathymetric scanners operating with green light, can penetrate the sea or river water and can be used for bed mapping. Also the terrestrial laser scanning technology (TLS) can be used for 3D point cloud collection and modelling of underground structures (e.g. caves) and later integrated with ALS data to generate continuously surfaces of the DTM and some new “underground DTM’s”.