Tree Height Estimation Methods for Terrestrial Laser Scanning in a Forest Reserve

A terrestrial laser scanning survey has been performed on a forest reserve site. This paper represents the processing of the dataset. Two new methods have been developed for tree positioning, which is necessary for height calculation. One of them is the clustering method, the other is the so-called crescent moon method. The stems were modelled, as high as possible, by both methods. Two methods were tested for height estimation. One was a direct method based upon the Digital Surface Model; however a new method was developed to predict the tree-top based upon the modelled trunk and then the nearest local maximum was selected to that predicted point in the DSM. The other was an indirect method, where the modelled stems were described as paraboloids, and the heights were extrapolated. The accuracies of the methods were investigated by means of photogrammetric measurements based on very high-resolution aerial images. Both the clustering and crescent moon methods were appropriate in tree positioning and stem modelling. The height estimation based upon the DSM yielded good results. The extrapolation method was tested for European Larch only. The height in one-third of the cases was estimated by this method within tolerance. This method can be taken into consideration in the case of leaves on scanning in very dense, multi-storey forests.