Airborne traffic monitoring in large areas using LiDAR data -theory and experiments

This article investigates the theoretical background for airborne LiDAR (light detection and ranging) and ALS (airborne laser scanning) systems that are used to monitor traffic from airborne platforms. An object moving with a velocity deviating from the assumptions incorporated in the scanning process will generally appear both stretched and sheared -motion artefacts. To study the impact of these deformations on the ALS data, the analytic relations between an arbitrarily moving object and its conjugate in the ALS data have been examined and adapted to concrete airborne specifications. Furthermore, a complete scheme is proposed to analyse urban traffic in real-life situations, which combines vehicle detection successively with the motion classification method, which is the main focus of this article. Finally, the velocity of the moving vehicle can be derived with knowledge about the vehicle shape. The experimental results obtained by using real ALS data were assessed with respect to the reference data concurrently acquired by a video camera to validate the theory.