Visibility analysis and related topics

There is a live web cam on Saentis. Is Lake Constance visible from there right now? If it is not visible is it because of the terrain? See the Säntis Webcam.

The question of whether something is visible from a viewpoint is asked quite often and in different variations. Visibility of an object in the terrain depends on quite a lot of factors like terrain, atmospheric conditions, and soil coverage. We will focus on terrain here, but keep the other factors in mind.
The table below lists some questions that are related to visibility. They are all based on the same basic visibility problem but some of them require further steps in order to be answered. The column on the right assigns terms that will be discussed later in this unit.

Question	Related terms
Can a place in the terrain be seen from a certain viewpoint?	Intervisibility, line of sight (LOS), profile
What area is covered by the services of a radio antenna?	Viewshed
How can an aesthetically unpleasant building be optimally hidden in the terrain in order to preserve the beauty of a landscape?	Viewshed (the other way round)
Where is the horizon to a given viewpoint?	Horizon line
Where can radio antennas be placed in order to minimise costs and optimise services?	Viewshed, watchtower problem
What is the potential direct solar irradiance at a certain location?	Irradiance mapping, cast shadows

Learning Objectives

You know what external effects have to be taken into account when using terrain data for a visibility analysis.
You understand how a line-of-sight (LOS) check can be performed for grids.
You know how questions related to the watchtower problem and moving viewpoints differ from simple intervisibility problems.
When you perform a visibility analysis, you know where uncertainties arise from and you know ways to deal with them.
You know the input parameters for modelling the potential direct solar radiation in rugged terrain.