From Wikipedia: In geometry, an angle is the figure formed by two rays, called the sides of the angle, sharing a common endpoint, called the vertex of the angle. Angles are usually presumed to be in a Euclidean plane, but are also defined in non-Euclidean geometry.
I am trying to automate a calculation of the blocked fraction of a field of view from a point to a shapefile. I.e. find α in http://i.imgur.com/2rWYC1O.png , such that α / 360 gives me the fraction of ...