Evaluation of airborne laser scanning data for tree parameters and terrain modelling in forest environment

Abstract

The aim of this article is to analyse possibilities of airborne laser scanning (ALS) data utilization in forestry, especially for the purposes of terrain modelling and for forest inventory (determination of forest height, diameter breast height and volume - DBH). The accuracy of ALS data in forestry was tested on the area of 1.5 ha. On this area the topography and location of all trees as well as their heights were surveyed in detail by means of total station. Firstly, the altitudinal accuracy of ALS for the creation of digital elevation model (DEM) was evaluated, based on the comparison with relief measurement. The research also evaluated different data sources from various types of scanners with a different point density per m2. Further, we compared tree heights determined from ALS data by different ways of interpolation into canopy height model (CHM) with the surveyed data, following calculations of DBH (diameter breast height) and tree volume based on the regressions. The results show sufficient data accuracy for the creation of DEM. Concerning tree height determination, the data is also useful although the accuracy is slightly lower, there is a slight undervaluation of the tree heights. Concerning using high point density data at full waveform scanner it is also possible to detect skidding tracks and micro-relief details. Anyway we did not find sufficient accuracy for DBH and tree volume at the scale of individual trees, but ALS data still gives better results for tree height, DBH and timber volume for larger forest stands than usual inventory.