A system and method for calculation of the duration a target area included within an image stream utilizes a three-dimensional model of at least one target area within a site. A counter is incremented during periods, for example on a frame-by-frame basis, when the target area is included in the image stream.An occlusion parameter is calculated for adjusting the calculated duration that the target area is included within the image stream. The occlusion parameter facilitates accounting for variations in a target area obstruction and is used for making adjustments to a counter so that a count indicative of a duration reflects variations in obstructions of the target area. A foreground parameter associated with target area is calculated for adjusting the calculated duration of the target area. The foreground parameter facilitates accounting for variations in the viewability of an image included within the target area resulting from various camera zooms.