Representation and computation of the spatial environment for indoor navigation

We introduce a spatial representation, s-map, for an indoor navigation robot. The s-map represents the locations of obstacles in a planar domain, where obstacles are defined as any objects that can block movement of the robot. In building the s-map, the viewing triangle constraint and the stability constraint are introduced for efficient verification of vertical surfaces. These verified vertical surfaces and 3-D segments of obstacles smaller than a robot, are mapped to the s-map by simply dropping height information. Thus, the s-map is made directly from 3-D segments with simple verification, and represents obstacles in a planar domain so that it becomes a navigable map for the robot without further processing. In addition to efficient map building, the s-map represents the environment more realistically and completely. Furthermore, the s-map converts many navigation problems in 3-D, such as map fusion and path planning, into 2-D ones. We present the analysis of the s-map in terms of complexity and reliability, and discuss its pros and cons. Moreover, we show the results of the s-maps for indoor environments