"Maps, directions, and location-based apps depend on data services. These data services are subject to change and might not be available in all geographic areas, resulting in maps, directions, or location-based information that might be unavailable, inaccurate, or incomplete. Compare the information provided on the device to your surroundings and defer to posted signs to resolve any discrepancies."
Source: https://support.apple.com/en-us/HT203033