Detection of range errors due to occlusion in separated transceiver LADARs

Laser detection and ranging sensors or LADARs are widely used in mobile robotics as sensing mechanism. When processing LADAR data for the purposes of feature extraction and/or data association, most previous works model such devices as processing range data which follows a normal distribution. In this paper, it will be demonstrated that commonly used LADARs with separated transmitter and receiver configuration suffer from incorrect range readings at range discontinuities due to occlusion, a much more detrimental effect on feature extraction or data association algorithms than random noise. The occurrence of these errors can be reliably predicted by monitoring the received signal strength. A useful design criterion for the optical separation of the transmitter and receiver is derived for non-coaxial LADARs and the exact environmental conditions which can cause range errors is quantified so that such errors can be reliably predicted.