A system and related methods for location determination aboard a subject vehicle not equipped with a GNSS-based positioning system receives position signals transmitted by non-satellite atmospheric vehicles and surface objects, which may include precise locations of the transmitting objects or position metrics associated with containment regions within which the transmitting objects should be to a particular certainty level. The received position signals may include ADS-B signals transmitted by proximate aircraft and facilities. The system may determine ownship location via multilateration of received position signals, via processing the received position metrics and corresponding containment regions, or via combining or correlating the two to determine accurate ownship location data of the subject vehicle.