I took screenshots of various parts of the island in edit town mode, then tried to stitch them together in gimp.
This bit felt really difficult because each screencapture I took didn't match up with the rest. The angles, scales and perspectives were all different, even though I just used my keyboard arrows to float around and didn't zoom or twist the view.
In the end I hatchetted them together then did the best I could by drawing a simplified image over the top.
It isn't finished yet but I uploaded it so you could get the idea.

Is there a simpler and quicker way to export a top down view of a whole map without distortions?