PROBLEM TO BE SOLVED: To decrease the data quantity and to acquire the three-dimensional geographic features, which can secure a natural impression, by omitting evenly the apexes of parts that can be planarly approximated and leaving the shapes of the geographically projecting parts as they are. ;SOLUTION: A patch setting means 2 inputs the space coordinates of plural points and sets the patches of triangles defining these coordinates as apexes every three points. A set of these patches form a mesh to show the three- dimensional geographic features. An apex omission means 3 inputs the mesh data and detects the parts which can be planarly approximated to omit the apexes of these parts. A mountaintop/ridgeline decision means 4 inputs the data on the mesh simplified by the means 3, etc., and decides the apexes equivalent of the mountaintops and ridgelines and the patch border lines. Then, an apex storage means 5 decides the apexes included within a prescribed distance as those to be stored among the detailed mesh apexes based on the mountaintops and ridgelines.;COPYRIGHT: (C)1998,JPO
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