Line-of-sight (LOS), also called "viewshed analysis," can be used to determine what can be seen from a particular location in the landscape. Conversely, the same analysis also determines from where within the surroundings that location can be seen. The first prerequisite for an LOS analysis is obviously a three-dimensional surface model of the landscape. For most applications, the most meaningful result would take vegetation, buildings, and other objects into account - those features that are purposely removed from bare-earth digital elevation models (DEMs). Above-ground features are generally included in Digital Surface Models (DSMs) created from lidar data.
LOS has many potential uses in community planning and zoning, airport operations management, event security, or battlefield cover and concealment, for example. Most students immediately think of cell phone tower placement as an application for LOS. While topography certainly has an impact on cell phone coverage, as in the case of flood inundation, modeling cell phone signal propagation is in reality a much more complicated problem. An LOS analysis can be useful for planning cell-phone tower placement, but, to truly model cell phone coverage, more sophisticated models must be employed.