Abstract: A method for processing and analyzing digital terrain data utilizing Digital Terrain Elevation Data (DTED). The method comprises defining approach azimuth and visibility limitations angle which are used for defining directional fans by determining fan opening angle, fan azimuth, and maximal range for terrain analysis. At least one directional fan data set is constructed from at least one source point within the DTED, where the directional fan includes line of sight information between said source point and DTED points located within said directional fan. The method further comprises interrogating said data sets by one or more queries to obtain terrain information for given approach conditions.