TIN from Contours and Medial-Axes
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TRIANGULATION OF DLG CONTOURS
AND MEDIAL-AXES

The picture on the left shows the source contours (brown), their medial-axes (red) and the TIN derived from them. Part of the contours are as extracted from a USGS DLG file while others were re-configured to look insolvable to other automated conversions, such as mountain passes and terraces. The triangles are colored to facilitate visualizing the polygons shaped by adjacent contours. The TIN file is structured on the basis of those polygons. Any triangle, without exception, is supported on both a source contour and a medial-axis. The pointers associated with each triangle facilitate the navigation from a triangle to its adjacents, from a polygon to the next, and from a map sheet to their neigbours. An instance of the usefulness of those pointers is a TIN contouring (See next page) made without any exhaustive searches across the TIN. For more on this work please see A Faithful Conversion of Contours in Proceedings of the ASPRS/MAPPS Conference on Terrain Data: Applications and Visualization - Making the Connection. Charleston, South Carolina, October 28-30, 2003.