There is some good discussion going on here..........my conclusion so far is that thinking out of the box and trying new techniques is never a waste of time......always something valuable is learned.
3km by 3km = 12000 x 12000 in pixels?
Actually 15,000 by 15,000..........likely beyond the reach of most computer's system resources.......at least for now. My first computer was a hotrod 386DX with 16 meg of ram!!!! We have come a long way since then.
The downside atm is that the Axis never raged war in the US. And its pretty damn hard atm to find DEM (or related formats) maps of Europe. At least as far as I know.
That is rapidly changing G. Mooyman, there is an amazing growth in this field. For the present, Nasa's SRTM data sets are the only free data available for International regions. There are a number of local municipalities that have 3min resolution images available in Geotif format. It does take some scratching around to fine them though. You might want to get in touch with Buck Compton for some contacts in Europe. 3DEM does have its limitations in that with lower resolution data sets the image can't be made large enough to bring it to actual scale for CC. Actually that is not entirely true........the 3D VRML viewer included can output a large image but any texture overlay will look pretty ragged by then..........using larger scaling on your textures might help..............
I've got another trick up my sleeve using a different program.......will let everyone know how it works out.
There is a small program (plt2dem) that works in conjunction with OziExplorer that can generate a dem from track files that have been overlayed onto the topo lines and then assigned elevations.
Quicker to go with the SRTM data......One word of caution for SRTM data, it will reflect off of a forest canopy giving a false elevation for heavily wooded areas. Genesis II had a similar utility but was NOT user friendly. Ozi3D has its limitations too.....the output file is proprietary, so piecing a bunch of screen captures together is the only option.......time consuming but do-able.
So it would seem, at least for now, IMHO there is no EASY way to create historically accurate maps based on true elevations.