Volume 26 Issue 2 - Publication Date: 1 February 2007
Special Issue on the Fifth International Conference on Field and Service Robotics, 2005
An Efficient Extension to Elevation Maps for Outdoor Terrain Mapping and Loop Closing
P. Pfaff, R. Triebel and W. Burgard Department of Computer Science, University of Freiburg, 79110 Freiburg, Germany
Elevation maps are a popular data structure for representing the environment of a mobile robot operating outdoors or on not-flat surfaces. Elevation maps store in eachcell of a discrete grid the height of the surface at the corresponding place in the environment. However, the use of this 212 -dimensionalrepresentation, is disadvantageous when utilized for mapping with mobile robots operating on the ground, since vertical or overhanging objects cannot be represented appropriately. Furthermore, such objects can lead to registration errors when two elevation maps have to be matched. In this paper, an approach is proposed that allows a mobile robot to deal with vertical and overhanging objects in elevation maps. The approach classifies the points in the environment according to whether they correspond to such objects or not. Also presented is a variant of the ICP algorithm that utilizes the classification of cells during the data association. Additionally, it is shown how the constraints computed by the ICP algorithm can be applied to determine globally consistent alignments. Experiments carried out with a real robot in an outdoor environment demonstrate that the proposed approach yields highly accurate elevation maps even in the case of loops. Experimental results are presented demonstrating that that the proposed classification increases the robustness of the scan matching process.
Multimedia Key
= Video = Data = Code = Image
Example 1: Incremental registration of two original point clouds. (1.1 MB) GIF
Example 2: Triangulated mesh representation of the outer loop including data points from 77 laser scans. The extension shows a virtual walk through this model on the trajectory taken by the robot. (5.2 MB) mpg
Return to Contents