Dtm Generated from Lidar Data under Forest Conditions

Since laser scanners systems became operational working tools, there have been many studies carried out to find the best way of their utilization. Generating a digital representation of the Earth surface and / or land cover has proven to be the biggest advantage of Light Detection and Ranging (LIDAR) data. The main objective of the presented study is to find out if there are any variations in accuracy between different resolutions of Digital Terrain Models (DTMs) generated from LIDAR data acquired in two seasons. The presented study was carried out in the forest range Głuchów, central Poland, owned by Warsaw University of Life Sciences in Warsaw and containing different types of forests: from one layer stands of Scots pine (Pinus silverstris L.) to multilayer and mixed stands with Birch (Betula), Alder (Alnus) and Hornbeam (Carpinus betulus L.). Generally flat relief covers the study area, with mean height above sea level around 185 m. The Falcon II airborne laser scanner system from Topographische Systemdaten GmbH (TopoSys, Biberach Germany) was used for LIDAR small footprint data acquisition. For this analysis the data of a flight in May and August 2007 were used. Ground survey data were recognized as reference data. During the 2007 and 2008 field sessions, 95 points spread throughout the area were measured. DTMs were generated in TreesVis software (FELIS, Germany). Models with 1 m, 2 m, 3 m, 5 m, 10 m and 20 m spatial resolution were interpolated. Results showed that if the bias error will be removed from data, even in forested areas measured in spring we can expect a DTM accuracy of 10 – 30 cm, comparing to reference data, for raster resolutions from 1 m to 20 m. Digital ground models up to 5 m can be generated in forested areas without significant statistical differences.