I wanted to try out the prayer that gives you a map, so i did. Boated my way up to an area i hadn't mapped yet, and yep, I got a local map (quality 4?) in my inventory.
It was blank. This probably has something to do with the fact that I used it in a local map area that contains the invisible edge of the world. Waste of 10 Numen points.
In a related note, the grid edge is actually about 125 tiles away from the edge of a local map, and the edge of the grid doesn't lie on the far edge of regional map, but in the second column of the 5x5 region map. Makes it impossible to get a complete area map along the edge.