Method of sampling a terrain data base

A method of providing intervisibility calculations for known terrain using a computer comprising the steps of:

• providing a digital terrain elevation data (DTED) database which models the known terrain and has data posts corresponding to points on the known terrain, the data posts being individually addressable in X and Y dimensions wherein spacing between adjacent terrain points varies as a function of at least one of said X and Y dimensions;
• identifying a threat data post by X and Y dimension values;
• identifying a set of radials of length corresponding to said constant radius and emanating from said threat data post;
• dividing said at least one of said X and Y dimensions into a plurality of sub-zones and for each sub-zone identifying a data post spacing value in said X and Y dimensions corresponding to terrain point spacing therein;
• traversing at least one of said radials by identifying a plurality of delta X and delta Y value pairs based on an angular orientation of said at least one radial, said plurality of delta X and delta Y value pairs are scaled according to said plurality of sub-zones, further identifying a given delta X and delta Y value pair from said plurality of sub-zones according to said threat post X and Y dimension values, and successively sampling along said at least one radial by successively accumulating said given delta X and delta Y values to identify successive sample points along said at least one radial whereby sampling at a given number of said successive sample points provides sampling along said at least one radial to said given length;
• and
• calculating intervisibility of the sample points with respect the threat point.