Automatic Determination of Forest Inventory Parameters Using Terrestrial Laserscanning

Abstract

In the Natscan project terrestrial laser scanning is used for deriving detailed information about tree quality and forest stand parameters. The authors describe an automatic method for determining tree positions and diameters at breast height (DBH) using terrestrial laser scanner data. Special attention is given to the data-processing that must be carried out before this information can be derived from the raw data. First, a digital terrain model is calculated by creating a subset of coordi-nates containing lowest Z-values. Subsequently, filter methods are described to delete any noise points which result from the ambiguity problem connected with phase difference scanners. Finally, the process of tree stump coordinate and DBH determination by using Hough-transformation and circle approximation is described. In comparison with a conventionally measured reference data set results for the stump coordinate and DBH are very promising. The differences fall within the expected range, although some im-provement on developed algorithms is still necessary. The information derived so far can be used a basis for further automatic determination of other single tree characteristics such as tree species, tree height, crown projection area as well as location and type of wood defects.