Looks very good Brian. Are these satellite radar images generally available?

One of the problems would be with resolution. Generally I need to model a very small patch of earth's surface (50m x 50m max), with contours at 1/2m or 1m intervals...it's unlikely that such data will be easily available to ordinary folks any time soon!

What we really need is a hand-held combined GPS/altimeter. Wallk (or drive) over the land pushing a button every now and then. Come home, plug the data-logger into the computer and there is the terrain map!