1. A video processing system comprising: an up-stream video processing device to accept an input video sequence and to output target information derived from at least one target in said input video sequence, wherein said target information comprises at least one target property or at least one function of said at least one target property; and a target property map builder, coupled to said up-stream video processing device to receive at least a portion of said target information and to build at least one target property map for at least one target type, wherein said target property map comprises a statistical model based on a record of said at least one target property from instances of at least one target type or said at least one function of said at least one target property from instances of said at least one target type in said input video sequence, wherein the statistical model corresponding to an image location, target property or function of target properties and target type is a record of said property of all instances of targets of said type that pass through said location.