Sweep-line-based filtering of airborne laser scanning data

Abstract

Airborne laser scanning (ALS) is the most recently emerged technology for acquiring Digital Terrain Model (DTM). In order to generate DTMs from ALS data, the terrain points and off-terrain points should be classified. To meet the objective, a sweep line based filtering algorithm was proposed in this paper. This algorithm works on raw range data obtained by ALS system without interpolation. The algorithm includes 3 steps. First, the point cloud is divided into sweep lines. The second step is to classify terrain points and off terrain points within each sweep line by choosing suitable tolerance value of height difference and size of filtering window. Finally, the filtering results of each sweep line are collected. Experimental work is conducted on 5 data sets of various terrain environments. A quantitative assessment was conducted to compare this result with manual classification. Both qualitative and quantitative experiments show that sweep line based filter can remove most of the off-terrain points effectively. Compared with other algorithms, sweep line based filtering is featured by simplified the 2-dimentional problem into 1-dimentional problem where less computational resources are required.