The initial research

[Hai-Etlik]

It sounds like you might be getting into the realm where GIS would actually be a good idea than massive overkill. Campaign Cartographer and friends are essentially just specialized graphics editors. Real life maps are largely produced with GIS software, though finishing touches may be done with graphics or layout tools. A GIS allows for shifting data layers around, altering their symbolizaton, and overlaying them to produce new data (such as intersecting temperature and moisture to get an aggregate climate layer.)

Probably the hardest part is going to be the DEM (Digital elevation model). Making a DEM that looks good is a lot of work and need yet more specialized tools. There are a lot of quick and dirty DEM/Heightfield generators out there but they all suffer from well, looking like quick and dirty terrain generators. They generally rely on various kinds of recursive noise generators based on fractals or the Perlin algorithm which all give overly consistent and unnatural looking results. In particular, they don't vary in frequency the way real landforms do. They also lack tectonic effects and usually erosion effects as well.

I've written a partial introduction to QuantumGIS (an Open Source GIS) in the tutorials section if you want to give it a try: http://www.cartographersguild.com/sh...-for-using-GIS