Bravo. A question, though (my GIMP-fu is nonexistent): can the Gimp provide this map with a bit of finishing stress? As it is, it looks very aggressively digital ... perfectly-sharp/crisp lines, symbols and labels.
In Photoshop, this could be amended pretty easily in the middle stages with a bit of screened noise, a soft blur, and a re-firming of the "spot ink" by adjusting the contrast - voila. What would be (if you have time) the comparable procedure for those of us just getting our toes wet in Gimp?