<title>Reference Preparation For Radiometric Update Systems</title>

Abstract

The Department of Defense has applications for radiometric navigation update systems and thus an ongoing need for improved radiometric reference map preparation procedures: more automatic procedures that produce more widely applicable data bases. An existing radiometric reference map preparation procedure is described that involves screening suitable navigation update sites, preparing temperature maps, and validating the temperature maps. The screening is partly manual (a photo interpreter looks for radiometrically unstable boundaries or insufficient spatial detail) and partly automatic (a computer evaluates the proportions of various materials). Temperature maps are automatically prepared from material region maps which are prepared by a photo interpreter tracing boundaries and identifying materials. Mission tape (temperature map) validation is by detailed simulation. We recommend replacing the manual screening techniques with automatic boundary evaluation. Instead of manual boundary tracing and material identification, we recommend region growing and boundary extraction techniques. Reference maps are needed since a radiometric navigation update system compares (using pattern matching or correlation) a sensed scene with a prestored reference map to estimate position. The terrain sensor detects energy reflected and emitted by the ground in portions of the millimeter wave band (usally at 35 or 94 GHz).