A Morphological Reconstruction Algorithm for Separating Off-terrain Points from Terrain Points in Laser Scanning Data

During the last decade various techniques have been proposed to extract the ground surface from airborne LIDAR data. The basic problem is the separation of terrain points from off-terrain points which are both recorded by the LIDAR sensor. In particular geometry driven filtering, detection or classification procedures are developed which use knowledge to find points, e.g. on buildings or vegetation. Depending on the application the off-terrain points are excluded from further processing, e.g. for DTM generation, or used, e.g. for building reconstruction. In this paper a new method is proposed to separate 3D off-terrain points from the terrain points. Morphological grayscale reconstruction plays the key role in the proposed algorithm to produce the bare ground. After a short description of morphological reconstruction an algorithm based on this technique is presented. Issues of the implementation of the morphological reconstruction algorithm are discussed and illustrated. Experiments are carried out with different LIDAR data sets, which point out the capacity of the process.