Date: 06 Jan 97 01:47:44 From: "Mark A. Brown" <email@example.com> References: 1
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Re terrain matching methods, there is another method which can be employed in addition to simple linear profile matching to improve accuracy, and that is terrain type matching. The strength of the returned radar signal depends on the type of surface over which you're flying -- woods, open fields, concrete jungle, water etc. This information can also be used for navigation to supplement terprom, provided that you have suitable information in the database. Of course, cruise missiles don't just use terrain matching but also have inertial guidance systems. IRSs tend to drift after a while, however, so a terrain referenced system can be used to improve the nav system accuracy. It doesn't matter if your terrain profile is slightly innacurate, as the system can "dead-reckon" on IRS until it finds a reasonable match. For CFIT, I suggest that the terrain model doesn't have to be all that accurate, so long as it is a "convex hull" for the real terrain (i.e. the bounding polygon surface encloses the real surface completely). After all, you're not using it for high-accuracy navigation but merely to avoid flying into the ground. Surface features like gullies and ravines, which are largely irrelevant, can be smoothed out of the model safely, giving great benefits for storage. Mark.