We propose an approach for OTF ambiguity resolution tightly coupled with the DGPS/INS estimator, where we add the states of carrier phase ambiguities and calibrate them along with the INS drift errors. Without any special ambiguity search and testing algorithm, we can resolve the ambiguities by the DGPS/INS estimator and improve navigation accuracy. We also get the improvement of the availability and continuity even though a single frequency GPS receiver is used. This system, named carrier DGPS/INS hybrid navigation system, is evaluated by the theoretical error analysis and flight experiments. Both results show the system enables precise approach and landing under the Category III conditions.
