If these programs would just support a few of the major coordinate systems (Geographic, UTM, etc.) then any existing georeferenced data could be used easily, and no manual matching or 3rd party terrain/overlay combinations would be needed. You could download data directly from the source and as long as it was already georeferenced (as most GIS data is), it would align properly, at least to the limits of the georeferencing accuracy. Programs like 3DEM and Global Mapper already do this, of course. And while these are considered GIS features, with the increasing interest from users of programs like Vue and Terragen in realistically depicting natural places, and the widespread free public availability of this kind of GIS data, it seems only logical for these software programs to at least be able to read (if not edit) GIS formats and their embedded georeferencing. Allowing this would save everyone a lot of work. - Oshyan