Kepler hit the nail on the head. Aerial and satellite imagery provide information that most maps can't. And I'm a map nut. Put both together (and throw in some track charts to boot) and you can get a pretty solid idea of what a place is all about before you've been there. Or see what's changed at a place you haven't visited in 10 or 20 years. I've used Googleearth, Googlemaps, Terraserver, etc., to locate unmarked trails or roads, tree-less vantage points, and other neat stuff. I recently spoke with one magazine editor who used Googleearth to nail down the exact track arrangement at a certain interlocking he needed to create a map for. Turned out to be more accurate than the standard map he had been given. On the flip side, another magazine is still noted for having published a two-page map on the snowsheds of Marias Pass, and they showed more sheds than there really are and most of them were shown grossly out of position. Imagery available on the web, and even the existing USGS topos, would have helped them print a more accurate map.