This is a project I have been working at off and on for the last month or so. I wanted to see if I could map out a large area and get it fairly realistic. I chose an area along the Red River at the border of North Dakota and Minnesota as the DEM data is at a really nice 1/9 arc second resolution. There is also some really high resolution orthophotos for the area to help map out the trees etc.
I started with the DEM data and merged a few quads together to give a nice area. I then brought that into photoshop to start working on the masks. So far I have a river mask, paved road mask, dirt road mask, forest mask, wheat field mask, green field mask, light green field mask and a farm areas mask, as well as bump maps for most of the fields and forest areas.
The full area mapped out is currently around 10km x 10km
There are quite a few things left that I would like to do including better texturing, more vegetation and adding all the farmhouses, barns etc.
Here are a few sample renders from different areas, with more to come eventually.