Any roadmap you buy will have at least one deliberate, obscure error, and typically more. The purpose is copyright protection. If someone puts out a copy of your map, but defends by claiming that he produced it independently (by going to the same sources you used), you can refute him by showing that his version has the very same map error you had hidden in your version.

The equivalent, in the counterintelligence community, is the "canary trap", used where one member (identity unknown) of a group is leaking information to the enemy (the "canary" singing). You distribute copies of a document to the group members, but with tiny differences planted among the copies. Later, you can identify your canary by noting precisely which version falls into the enemy's hands.