Now this <http://sobo.cr.usgs.gov/QM/QMsoftware.htm> looks like a GEM application (it seems to use the VDI, at least) that no-one's noticed before. I've not managed to get it working, but maybe one of the other posters will have more luck. Moral: When you think of a good search string, try it on Teoma as well as Google. -- John Elliott