Actual viewsheds from 11 viewpoints were field surveyed and compared to pre
dicted viewsheds generated using various commonly used elevation data sets,
various data models, and various visibility criteria. It was found that so
me data sets produced predicted viewsheds that mimicked surveyed viewshed m
uch more accurately than other data sets, and that some combinations of dat
a models and visibility criteria produced much greater matching accuracies
than other combinations. However, none of the combinations of data source,
data model, and visibility criteria produced predicted viewsheds that match
ed surveyed viewsheds with much more than 50 percent accuracy. Some possibl
e reasons for this lack of accuracy are proposed.