Distance-weighted isovist area: An isovist index representing spatial proximity

• A mathematical model to weight isovist area is presented.
• Distance between an observer and surrounding areas is used for weighting.
• The distance-weighted measure is interpreted in a geometrical method.
• The distance-weighted isovist area represents spatial proximity.
• The effect of weighting functions is demonstrated using two hypothetical cases.

A method of calculating the isovist area weighted toward its origin point is presented. Although weighting area is a general idea, a specific method or its tangible implementation has been rarely established in the field of isovist analysis. The distance-based weighting is implemented by substituting the distance between the isovist origin and a point on the isovist boundary with a user-defined function. This substitution allows an arbitrary function to be used for the weighting. Emphasis on the proximate region results from, but not limited to, the use of a function with a non-increasing derivative. Three plausible attenuation functions are used to exhibit the effect of an attenuation function on weighting. The proposed weighted isovist area is compared with the conventional isovist area and other isovist indices. The comparisons show a noticeable difference of the proposed method. Therefore, the proposed weighted isovist is a potential tool for research in spatial cognition, and human behavior, in particular, when proximity to an observer needs to be considered. Work environments in a construction site and other issues involving proximity can be assessed as a part of construction site layout planning.