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; 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 instances of targets of said type that pass through said location, and wherein the statistical model represents at least one of a normal behavior or a normal property of instances of targets of said type that pass through said location; and the target property map builder being further configured to, for a given target: consider at least one instance of the target; determine if said at least one instance of the target is a bad instance, and if said at least one instance of the target is a bad instance, filter said at least one instance of the target by ignoring said at least one instance of the target.