The invention includes a step S1 for inputting into a computer coordinate values on a three-dimensional shape; a step S4 for structuring an environment model that partitions a spatial region, in which a three-dimensional shape exists, into a plurality of voxels of rectangular solids, and stores each position; and a step S5 for setting and recording a representative point and an error distribution thereof, within the voxel corresponding to the coordinate value. If there is no data in a previous measurement position, position matching is performed in a fine position matching step S7 so as to minimize an evaluation value regarding the distances between adjacent error distributions by rotating and translating a new measurement data and error distribution for the environment model for a previous measuring position, or rotating and translating an environment model for a new measuring position, relative to an environment model for a previous measuring position.