The Graph 18 Surface Locator served as a directional transponder for navigation purposes on the surface of a planet. By analyzing star-charts and gauging solar and lunar angles, the transponder was capable of self-location, in addition to determining planetary north and south. This device, which held in excess of 25,000 planetary maps, was able to receive updates via connection to the Alliance MasterNav. About the size of a typical briefcase, the transponder also featured the capability of direct connection to a droid's brain.