Did someone mention my name? Mike, buddy, of course. :) (Mike, we need to talk.. ya really have to stop associating me with them damn dem files! ) J/K

Earlier this year, I became aware of all sorts of nasty stuff about DEM files, so when the USGS started a mailing list, I signed up pronto. Seems that there are 5 or 6 variations of SDTS DEMs. The variations are mostly errors and omissions in the data. If any of us in the 3d art community think we're fustrated trying to get DEMs to align, imagine how folks who make a living using em feel. They're not a happy group. Even more fustrated, must be the guys who try to write utilities for merging and converting DEMs.

The last word from the USGS, was that as of Oct 1, 2001.. all SDTS DEMs avail from them, would be of the same format, with all corrections in place. What's weird is I haven't heard any varification that this is now true. Folks on the email list are just as unhappy as ever.

With all that being said, I suspect that even perfect DEMs won't align in Vue. Only the position will be correct. As was already mentioned, the edges of adjoining DEMs can't align. From my experiments (I'm no expert.. nor a code writer), the way apps like 3DEM work, is by filling in the gaps between edges, maybe even an averaging thing. I tried doing that manually once.. thousands of polygons for each edge.. won't try THAT again! :) Anyway, 3DEM is easy to use for merging, and you won't see that seam in Vue, even if you place the camera right on it.

For anyone who just wants to convert an SDTS DEM to a standard ASCII one, SDTS2DEM is a great utility that has been updated to work with post Oct 1 SDTS DEM files. I can't find my link at the moment, but the 3DEM site Mike linked can probably lead you to it.