The visual depth to location at any point ‘V’ in plan is the least number of ‘visual steps’ from said point to a single universal sample location. A ‘visual step’ is taken whenever a path passes across the threshold of all space visible from the start of the previous visible step (i.e. the isovist perimeter at that origin location).

The mean visual depth at any point ‘V’ in plan is the average total of visual steps from the point to all locations (Hillier, 1996). In scan form it illuminates visual centrality within a configuration.

The Isovist_App determines mean visual depth by averaging all visual step depths calculated from point ‘V’ to all successive stochastic global sample locations. In notation form the calculation for mean visual depth is  expressed as:

Where ‘Gi’  is the least number of visual steps from location V to a global sample location; and ‘n’ the total number of global sample locations.