Directed Visibility (Wv) expresses the proportion of the user defined subject region that a location can see, or, inversely, how often a location is seen from said region. Isovist_App Directed Visibility correlates to Area and Connectivity when just accessible space is analysed; but varies, introducing a degree of direction, once the sample region is restricted or when visible space isovists are included in the calculations.
To determine Directed Visibility, the Isovist_App generates isovists at stochastically selected locations in the sample region. It then records any point ‘V’ that falls within each isovist generated. The resulting ‘score’ at V is divided by the number of isovists generated overall to give a mean value. The result is a relative value between 0 and 1.
In notation form the calculation for Directed Visibility is expressed as:
Where ‘Hi’ is either 0 or 1 depending on whether point V falls within a sample isovist; and ‘n’ the total number of isovist samples.