Importance

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Abstract

A digital elevation database is compressed to create a compressed digital map database which is used by a digital computer system for displaying three-dimensional terrain data in the form of polygons. The compressed digital map database is produced from a database of elevation points by selecting every mth row and every nth column, thereby resulting in a reduction of database storage requirements. During program run-time the intersection of rows and columns forms cells with four corners. The elevation value of a center elevation point for each cell is formed by various methods, thereby creating a cell made up of four three-dimensional triangles. One method for creating the elevation of the center elevation point uses the elevations of the four corners of the cell. Another method uses extrapolated elevation values from the cell's extended diagonals. The three-dimensional triangles formed from the center elevation point are then transformed and projected using standard computer graphics methods on a digital computer to produce a three-dimensional projected display.

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First Claim