Two algorithms for determining partial visibility and reducing data structure induced error in viewshed analysis

In geographic information systems, viewshed analysis is used to calculate the areas on a topographic map that can be seen from a specified set of locations. Grid cell («raster») based viewshed routines typically create binary map results, in which each cell is listed as being entirely visible or entirely not visible. Prior research has shown that sampling errors in elevation data can reduce the accuracy of the resulting visibility maps. This study demonstrates that further errors may be introduced in binary viewshed maps by the geometry of the raster data structure itself. Two techniques are illustrated for reducing data-structure induced error in viewshed analysis