Effect of database errors on intervisibility estimation

One of the most common uses of digital terrain databases is in the evaluation of intervisibility, or clear line of sight, between points in space. These evaluations are often used to make decisions regarding deployment of equipment or personnel. However, there will be errors or discrepancies between the database and the true terrain, and, because of these discrepancies, the visibility in the field will differ from that predicted using the database. This paper describes a method for calculating the probability of visibility over an area for a given error specification. Results are described showing the sensitivity of visibility uncertainty to database error and terrain roughness. Sensitivity to other parameters is discussed. The results show that databases are very good for predicting masking but are less reliable for predicting visibility. Also, the reliability of the visibility predictions increases with increasing terrain roughness.