Faster Line of Sight Computation and Faster Viewshed Generation

The R3 Viewshed Algorithm is widely used in the Geographic Information System (GIS) industry as it generates an accurate viewshed. But, this algorithm is computationally slow as each and every point of all intermediate profile lines are tested for their visibility. Other available algorithms, although faster, only provide an approximation of the viewshed. So, an accurate viewshed algorithm whose computational speed is faster is imperative. In this regard, a faster and accurate viewshed algorithm based on faster Line-Of-Sight (LOS) computation has been devised and implemented in this paper. The improvement is based on computation of LOS which separates the shadow regions whose visibility does not need to be tested. This significantly reduces the number of intermediate points for visibility analysis thus making the computation faster. Experimental tests were carried over the geographic database of 48,000 sq. km which included terrains varying from 58 m to 8,000 m. The obtained results have shown an average improvement of 24% in the overall viewshed computation.