Analyse quantitative de donnees laser 3D: Classification et modélisation du terrain

Airborne laser scanner technique provides a 3D perception of the terrestrial topography, including true ground and objects belonging either to vegetated areas or to human made features. The high intrinsic accuracy and regularity of airborne laser sensors makes highly conceivable the extraction of structural information related to the recorded 3D-points. In this respect, a new algorithm has been developed in order to classify the initial cloud of points into ground/non ground earth points and generate accurate Digital Terrain Models (DTMs) on a regular grid. Our approach is based on a multiple pass classification process. An estimation of the ground is performed within overlapping neighbourhood and laser points are classified with regard to this ground estimation. The algorithm moves toward the neighbour where the average altitude is the lowest. We then compare the vicinity of the terrain with the estimated ground and apply a linear correction. As it goes along, points are filtered many times until we vote for the final label. The estimated ground surface is then the input of an energy minimization algorithm (ICM) which consider laser points as a set of attractors. The final DTM will be a trade off between internal properties and its closeness to ground laser points. The resolution may be fine enough to proceed relevant micro relief analysis especially in a rural environment.