Tradeskill: Cartography

I have no real idea if this is possible, but I will put it on the table for thought.

I was thinking that the Big Book of Towns might be expanded to include new outdoor & above ground areas on a building percentage chance much like gemcutting and the like. If the PC makes the roll when entering an area already visited, then the map would open up to them. If not, then it is closed as usual. Nothing too fancy; just another way to encourage exploration, as well as revisiting some areas.

Thanks!