Flight Evaluations of Carrier DGPS/INS Hybrid Navigation for Automatic Landing

Masatoshi Harigae, Toshiaki Tsujii, Takatsugu Ono, Toshiharu Inagaki, Hiroshi Tomita

Abstract:	The DGPS/INS (differential GPS and inertial navigation system) hybrid navigation is one of the promising navigation methods for precise approach and landing. Comparing with the kinematic GPS navigation, it has the advantage in the dynamic range of sensor systems, variety of navigation data, the availability and continuity that are important characteristics for aircraft guidance and control during an approach and landing phase. However, in the point of positioning accuracy, it is inferior to the kinematic GPS navigation because it uses noisy pseudorange as a measurement. Its theoretical positioning accuracy is about 2 m in each axis, that is confirmed in the flight experiments [1]. There has been several approaches to realize a cm-level DGPS/INS hybrid navigation system implementing carrier phase for measurement updates [2], [3]. They proposed the method where the ambiguities are already resolved by a fast and robust OTF (On-The-Fly) algorithm and then carrier phase is used in the DGPS/INS estimator (Kalman filter). We propose an another 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. In this paper, we first show the theoretical results that confirm the observability of ambiguities in the DGPS/INS estimator. Then we evaluate the proposed algorithm in flight experiments. The experimental results show the improvement of positioning accuracy. Difference between the carrier DGPS/INS hybrid navigation with a single frequency GPS receiver and the kinematic GPS navigation using a dual frequency data is about several ten centimeters that is better than accuracy of the conventional DGPS/INS hybrid navigation.
Published in:	Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998) September 15 - 18, 1998 Nashville, TN
Pages:	437 - 446
Cite this article:	Harigae, Masatoshi, Tsujii, Toshiaki, Ono, Takatsugu, Inagaki, Toshiharu, Tomita, Hiroshi, "Flight Evaluations of Carrier DGPS/INS Hybrid Navigation for Automatic Landing," Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998), Nashville, TN, September 1998, pp. 437-446.
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