I'm currently researching certain ways to improve terrain and water rendering, not sure yet if anything good will come out of this.
One issue I came across: there's a cfs3h2o.dds file which defines sea color and covers the whole map (though it is flipped vertically). I need to find a way to calculate coordinates in this file based on world coordinates. Of course CFS3 already does it for its water, but so far I'm unable to reverse engineer that part.

For the stock CFS3 Western Europe I calculated that the map is a "square" (I guess the Earth if flat ) with a side of about 1560 km. However I don't know where this size comes from: is it hardcoded? Or is it somewhere in the game data?

I know there are other maps - Pacific Ocean and North Africa, but I don't have them installed and can't verify the size.
Are those maps the same size as the stock one? Or if they are different, what controls it?

The only remotely related thing I found is in cfs3europe.xml inside terrains\terrdata.zip:
<Terrain OriginLat="N48 0.0" OriginLon="E3.5 0.0" ...
These are indeed the coordinates of the center of the game map (SE of Paris), but I don't see anything about the map size.