A Practical Approach for Extracting Tree Models in Forest Environments Based on Equirectangular Projections of Terrestrial Laser Scans

Abstract

Extracting 3D tree models based on terrestrial laser scanning (TLS) point clouds is a challenging task as trees are complex objects. Current TLS devices acquire high-density data that allow a detailed reconstruction of the tree topology. However, in dense forests a fully automatic reconstruction of trees is often limited by occlusion, wind influences and co-registration issues. In this paper, a semi-automatic method for extracting branching and stem structure based on equirectangular projections (range and intensity maps) is presented. The digitization of branches and stems is based on 2D maps, which enables simple navigation and raster processing. The modeling is performed for each viewpoint individually instead of using a registered point cloud. Previously reconstructed 2D-skeletons are transformed between the maps. Therefore, wind influences, orientation imperfections of scans and data gaps can be overcome. The method is applied to a TLS dataset acquired in a forest in Germany. In total 34 scans were carried out within a managed forest to measure approximately 90 spruce trees with minimal occlusions. The results demonstrate the feasibility of the presented approach to extract tree models with a high completeness and correctness and provide an excellent input for further modeling applications.

Automatic reconstruction of skeletal structures from TLS forest scenes

“…We conclude that the segmented data raster with 2D skeletons of its components appears to be a suitable starting point for a prospective problem solution. To sum up, we agree with (Eysn et al, 2013) that a step-wise completion of tree skeletons from results of multiple scans may result in a fitting, robust skeleton.…”

“…in Z+F LaserControl, Trimble/Faro Scene. PTX (Leica Geosystems, 2012) is a plain text file format that provides 3D coordinates and intensity information in a raster arrangement As a result, there is no need to explicitly calculate and interpolate an equi-rectangular projection of the TLS data as performed by (Eysn et al, 2013) if PTX export is available. In the following, a point is associated with its 3D coordinates in the point cloud and at the same time with its 2D coordinates in the resulting data raster as retrieved from the PTX file.…”

“…Recently, an interesting approach has been presented by (Eysn et al, 2013), who manually sketch tree skeletons in an equirectangular projection of TLS data. Subsequently, the skeleton sketch is used for fitting cylinders to points in the skeleton's vicinity.…”

“…In this paper, we pick up the basic idea of (Eysn et al, 2013) and introduce a novel strategy to obtain skeletal structures automatically from surface patches via the Voronoi Diagram and subsequent Principal Curve computation as shown in figure 1. The paper is organized as follows: First, we explain our proposed strategy.…”

Fast and Robust Stem Reconstruction in Complex Environments Using Terrestrial Laser Scanning

“…For example, Buckley et al (2008) described the usage of TLS data in geology, Ghuffar et al (2013) used TLS data in combination with airborne laser scanning (ALS) data to monitor displacements of a landslide, Zogg and Ingensand (2008) used TLS for deformation monitoring of a bridge, Martínez et al (2012) used TLS data to extract building facades, and Eysn et al (2013) used TLS data for extracting tree models in a forest. However, for forestry applications several publications can be found in literature, using TLS data for extracting single tree parameters such as diameter at breast height (DBH) (Kankare et al, 2015), stem and branch models (Bremer et al, 2013), tree biomass (Calders et al, 2015), forest structure (Reid et al, 2014) or the forest terrain (Moskal and Zheng, 2011), just to name a few.…”