*Perimeter* (Pv) expresses the length of the edge of all space visible from a location. In isovist terminology, it represents the geometric isovist perimeter at said location (Benedikt, 1979).

To determine Perimeter at point ‘V’, the Isovist_App simply extracts the geometric perimeter value from the polygon of the isovist calculated at V. The outcome is an absolute value of length.

In notation form the calculation for Perimeter is expressed as:

*Where x _{i}, y_{i} is the coordinate of each vertex of the isovist polygon, and n the total number of vertexes of the isovist.*

*Closed Perimeter* (Uv) expresses the length of the closed edges (i.e. solid walls) of all space visible from a location. In isovist terminology, it represents the non occluded perimeter at said location (Benedikt, 1979).

To determine Closed Perimeter at point ‘V’, the Isovist_App calculates the total length of all occlusive edges of the polygon of the isovist calculated at V. It then subtracts that sum from the value of Perimeter (Pv). The outcome is an absolute value of length.

In notation form the calculation for Closed Perimeter is expressed as:

*Where E _{i.occ} is length of each occlusive edge, n the total number of occlusive edges of the isovist, and Pv, perimeter.*