If the map you are doing is your own version of the map, then I believe that is fair use, (Think of Anna's versions of Greyhawk, or someone else's version of Forgotten realms or Middle earth).

You did the work, and the work is based on a known entity.

However, you cannot post a copy of the original even if you claim it is not yours, as likely you do not have permission to post copies of it. You can post links to it.