----------------------------Original message---------------------------- I'm involved with the Highland County Cave Survey (VA). The project is intended to discover and detail caves in the area. At this time we are walking the county farm by farm, a difficult and time-consuming endeavor considering our small numbers. We would like to know whether infra-red imagery of the area would expedite our project by revealing near-surface heat sources. Ideally, the images should hav e been taken in winter in order to maximize the temperature differentials. Thanks Frank