Confronto tra tecniche classiche e metodi diretti multirisoluzione per la produzione di modelli digitali del terreno da scansioni LIDAR

This paper reports a comparison among different methods for the production of Digital Terrain Models for technical and mapping purposes, particularly in the case of mountain areas covered by dense canopy. The analysis is addresses to investigate on the diversities between the classical DTMs obtained from conventional aerial photogrammetric methods, and those derived from LIDAR techniques. In the performed tests, someDTMs of mountain forested areas have been produced by the digital map of the Friuli Venezia Giulia Region, extracting the points related to the altimetry, like isoline vertices and individual points of measured height. These DTMs have been compared with the corresponding ones produced by airborne laserscanner surveys. To this aim two different computation techniques have been adopted: the first was a semi-automatic filtering and classification, followed by a very accurate manual validation performed by a commercial software (TerraScan); the second one was a simple direct filtering method based on a variable dimensional cell grid analysis. The results let to evaluate the different methods adopted for DTM production. Worth of note, the cell grid method, despite its present basic approach, let to produce a DTM from LIDAR data with a metric quality and a grade of detail fully comparable and often superior (over forestry areas) than a digital map of large scale.