Instantaneous radio positioning method and system. Signals from a plurality of spatially distributed transmitters are received at a known reference position and at an unknown position to be determined. A composite of the radio signals, simultaneously including a component signed from each of the transmitters, is digitized and then processed to measure phases that is then digitized. Ambiguity is resolved by finding the location in parameter space of the maximum of an ambiguity function related to sets of phase-measurement data. Position is determined at a point in time without keeping track of phase history.