If you use one of the mapping clients, you could walk around a bit and then try uploading your set of maps.
See here.
If everything goes well, the server will tell you the supergrid you are in while you are uploading.
The supergrids are named as follows:

This greatly narrows down the area you have to scan for terrain shapes.
Since there seems to be some demand, I could also have the server tell you a more precise location that can be used to find your exact location using the grid on Algeralith's map.