An example of a technique for compensating for effects of Earth's magnetic field variations on a mobile device positioning system. A mobile device utilizes a compass to obtain an absolute heading when located relative to a visible light source. The mobile device obtains a heading correction value based on an identifier of the visible light source. An orientation of a map displayed on the mobile device is rotated based on the absolute heading and the heading correction value in order to provide an indication of a location of the mobile device properly oriented on the map.