tivation
The explosion of capabilities for collecting and distributing digital elevation data for terrain from around the world has led to a significant increase in the amount of computation required to exploit this information for problems where visibility is an important factor. Use of naive visibility determination algorithms results in much greater than linear increases in computation requirements as elevation dataset sizes increase. The increasing power of widely available workstations and personal computers invite exploitation of increasing volumes of terrain data. However, the straightforward use of existing visibility analysis procedures either degrades a significant amount of the information present in the original elevation data or imposes computational requirements far in excess of current or anticipated hardware capabilities when examining even modest real world problems. Various existing approximation methods reduce this complexity but can suppress the effects of relatively minor variations in terrain elevation that may have a major impact on visibility. Careful design and selection of visibility estimating algorithms and representations can make exploiting elevation data more computationally tractable.