Computational Mapping of the Ground Reflectivity With Laser Scanners

In this investigation, we focus on the problem of mapping the ground reflectivity with multiple laser scanners mounted on mobile robots/vehicles. The problem originates because regions of the ground become populated with a varying number of reflectivity measurements, whose value depends on the observer and its corresponding perspective. Here, we propose a novel automatic, data-driven computational mapping framework specifically aimed at preserving edge sharpness in the map reconstruction process and that considers the sources of measurement variation. Our new formulation generates map-perspective gradients and applies sub-set selection fusion and de-noising operators to these through iterative algorithms that minimize an l₁ sparse regularized least squares formulation. The reconstruction of the ground reflectivity is then carried out based on Poisson's formulation posed as an l₂ term promoting consistency with the fused gradient of map-perspectives and a term that ensures equality constraints with reference measurement map data. We demonstrate that our new framework outperforms the capabilities of the existing ones with experiments realized on Ford's fleet of autonomous vehicles. For example, we show that we can achieve map enhancement (i.e., contrast enhancement), artifact removal, de-noising, and map-stitching without requiring an additional reflectivity adjustment to calibrate sensors to the specific mounting and robot/vehicle motion.