Precise, very long range marine positioning with GPS: achieving sub-decimeter precision in a matter of minutes

In remote sensing over large areas with interferometric sonar, etc., that require high precision GPS geolocation, it is often desirable to achieve such precision in a short time. A technique for speeding up the convergence of the kinematic GPS navigation filter over long baselines has been tested. A buoy at sea has been positioned relative to base stations many hundreds of kilometers away. Sub-decimeter accuracy has been achieved in a few minutes, even when simultaneously relaxing the broadcast ephemeris to improve results. This fast convergence is commonplace in short-range surveys, when the vehicle is within 20 km of a base station, so it is possible to fix the carrier phase ambiguities to an exact number of cycles. But if a ship is operating in the high seas, achieving the same accuracy requires acquiring data for close to an hour, if carrier phase biases are "floated" in the usual way. In the method tested, the gradual change in mean sea level (after waves are filtered out) is used as a constraint to the solution