Aircraft Autonomous Integrity Monitoring for an Integrated Satellite/Inertial Navigation System

Stefan Vieweg

Abstract:	By turning to an operational status in near future Global Navigation Satellite Systems (GNSS) like the U.S. GPS and its Russian pendant GLONASS provide highest accuracy navigation capabilities when using differential techniques. In principle the po- sition accuracy can comply with ICAO-limits for precision approaches and taxi guidance (submeter respectively meter range), if the initial ambiguities and cycle slips in the phase measurement are detec- ted and adapted. For aviation applications under real environment se- veral effects onboard the aircraft like satellite mas- king, multipath, cycle slips, dynamic influences on the receiver, electromagnetic disturbance etc. de- grades GNSS integrity to an unacceptable level, so that even with sufficient satellites, GNSS would not be capable for sole mean navigation. Concerning system integrity checks of satellite na- vigation, two different approaches, Receiver Auto- nomous Integrity Monitoring (RAM) and ground based overlay techniques (e.g RGIC) with different advantages and shortcomings are in discussion so far, but none is able to compensate insufficiencies of the satellite systems concerning dynamic envi- ronment and reliability. Therefore inertial sensors are an ideal complement to GNSS, due to their good dynamic behaviour, alt- hough they are characterized by longterm drift as a result of misalignment, accelerometer and gyro errors. Their budget varies with dynamic manoeu- vres so that a preflight error determination and sy- stem calibration is impossible. Combining both, satellite and inertial system, via Kalman-filter techniques there is the ability to esti- mate and compensate separated sensor errors of the inertial as well as the satellite systems within a hy- brid, complementary navigation system. In result the demands in quality (i.e. accuracy as well as reliability) can be satisfied. Starting in 1989 the In- stitute of Flight Guidance and Controlpublically de- monstrated the feasibility concerning the accuracy aspect several times by means of automatic flight tests. In addition to the limitations of usual integrity mo- nitoring concepts for satellite navigation systems this paper shows an approach for reduction of these problems with the help of a hybrid GNSS-/Inertial- Navigation System. In this concept Aircrafl Auto- nomous Integrity Monitoring can be utilizied even under worse conditions (e.g. bad satellite geometry, non-redundancy of satellite information) when for example RAIM algorithms do not fit any more.
Published in:	Proceedings of the 6th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1993) September 22 - 24, 1993 Salt Palace Convention Center Salt Lake City, UT
Pages:	509 - 518
Cite this article:	Vieweg, Stefan, "Aircraft Autonomous Integrity Monitoring for an Integrated Satellite/Inertial Navigation System," Proceedings of the 6th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1993), Salt Lake City, UT, September 1993, pp. 509-518.
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