The selection of the minimal number of observers that ensures the maximum visual coverage
over an area represented by a digital elevation model (DEM) have great interest in many
elds, e.g., telecommunications, environment planning, among others. However, this problem
is complex and intractable when the number of points of the DEM is relatively high. This
complexity is due to three issues: 1) the di culty in determining the visibility of the terrain
from one point, 2) the need to know the visibility at all points of the terrain and 3) the
combinatorial complexity of the selection of observers.
The recent progress in total-viewshed maps computation not only provides an e cient solu-
tion to the rst two problems, but also opens other ways to new solutions that were unthinkable
previously. This paper presents a new type of cartography, called the masked total viewshed
map, and provides optimal solutions for both sequential and simultaneous observers location.