A FAST SOLUTION TO LOCAL VIEWSHED COMPUTATION USING GRID-BASED DIGITAL ELEVATION MODELS

A new algorithm for generating viewsheds from grid-based digital elevation models is presented. It uses a combination of sightline analysis and the relationships between the local surfaces at the source and destination points. Depending on the nature of the terrain surface, significant savings in computation time over existing sightline only based algorithms are made because a substantial proportion of the destination points can be determined as invisible from the source point without the need for sightlines. The new algorithm also produces more reliable results by better consideration of points at or near the viewshed horizon.