It's a bit too clean and precise to give a sewer feel but it will work fine for a PWYW product

This is so awesome, I am in the process of using it in one of my fanfiction stories. I just thought it was cool and would fit into Harry Potter considering that he had the map his father and friends made. But I thought about it and decided that theose mapping spells that created the map would be invaluable in their society and that it would be a very good money maker.