This is fascinating and it seems we share a great deal of ideas here.

So you get your basic consistency through using Bryce and rendering the terrain with a similar texture set. I am guessing then that you must model the terrain by hand based on some reference maps.

Your final size of 28Kx22K must be close to the limit of what your able to work with. My experience is that even if you had unlimited ram the basic image file formats tend to break down at about the 32K. My PSP start dying at 14K so its of limited use at these resolutions. Im guessing that you must have to turn off any undo buffers or any layer controls.

I am an admin on the Me-Dem site :- "www.me-dem.org". Were making a map of middle earth at an extrordinary resolution. I think the plan is 160K x 160K. Its nuts actually and we might not be able to go quite that high but thats the current plan. I am attaching an image of our base map which is also 3D contoured set. Its 10x10 tiles of 2048x2048 so its of similar size. This is the base DEM because it gets chopped into 256x256 tiles and then procedurally boosted up to 2048 each tile.

Most of us are running 64 bit XP and I am unusual in that I have a mere dual core as most of the others have quaddies. I would recommend getting 64 bit but you need to check if your apps are available in 64 bit or else it does make much difference.

One thing I must also ask. On another forum there was a chap putting together a new machine and thinking of getting 4Gb for XP 32 bit. I was very skeptical that you could get 4Gb out of it. Tell me, if you right click on My Computer and properties, what RAM does it tell you that you have installed. How much of your 4Gb do you think you have access to ?

Is your map an open shared thing or a commercial type ? The Me-Dem is open. I think the general rule is that if you register on the site then you can download the work in progress. You can get that 20K middle earth if you want it. If your map is open then I can suggest some more chewy stuff to help you out on it - especially if you find that your machine is practiucally dying under the load of it.

You map is very cool. Mucho kudos !