Nah, it's a map to Raftel. The Roger pirates gave him that tattoo, which has a cypher on it or has the exact necessary angles or whatever, in order for him to get back to Laugh Tale when the time arose. He was "the child of destiny" after all, probably meaning everyone considered him to be the promised 800 year old prophecy Joy Boy reincarnation.

Shanks let go of his arm with the map on it because Luffy ate the fruti and/or he came to believe Luffy would actually be Joy Boy. So he "bet it on a new era".