Also, you can only copyright that which is novel and created by you. The bit of the map that it is based on is someone else's copyright and the bits you added are yours. But if there is part of someone elses copyright works in your map your still at risk for the proportion of it that is protected. Also, you can only copyright an artistic work not an idea so you can have a completely novel map with novel names etc and say it is based in some book location and its ok. Just don't mention anything that was created in the book.