A system and method are disclosed to track aircraft or other vehicles using techniques including multilateration and elliptical surveillance. Unlike conventional approaches that use time difference of arrival for multilateration at a fixed set of reception points, this technique allows targets to be tracked from a number of dynamic or moving reception points. This allows for triangulation/multilateration and elliptical surveillance of targets from combinations of fixed, fixed and moving or only moving ground-based receivers, sea-based receivers, airborne receivers and space-based receivers. Additionally this technique allows for ADS-B validation through data derived from only two receivers to assess the validity and integrity of the aircraft self-reported position by comparing the time of arrival of the emitted message at the second receiver to the predicted time of message arrival at the second receiver based on the self-reported position of the aircraft and the time of arrival at the first receiver. The benefits of using less than three receivers for validation include greater validation coverage areas using a smaller set of ground stations at a lower infrastructure cost.