1. A method for determining a path of travel of an intruder traversing an area of regard (AOR) to a predefined point, where the path of travel has a minimum probability of detection relative to other potential paths of travel of the intruder, the method comprising: providing three dimensional terrain data concerning the area of regard; providing the locations of a plurality of detection sensors implemented in the area of regard, with each said detection sensor having a known field of view; providing a predetermined single scan detection probability for each of the detection sensors; generating a grid of points that is laid over the area of regard; using a computer processor to consider the grid of points, the three dimensional terrain data, and the predetermined single scan detection probability for each of the detection sensors, and to determine a particular path of travel, defined by arcs connecting selected ones of said grid of points, of said intruder to said predefined point that represents a minimum probability of detection of said intruder relative to all other potential paths of travel through said area of regard to said predefined point.