Cycle Slip Detection and Correction by Means of Integrated Systems

Christian Altmayer

Abstract:	Satellite navigation systems are widely used for today's high accuracy applications like automated vehicle guidance,aircraft precision approaches or flight measurement techniques demanding the most accurate ranging information obtainable, the carrier phase observable. Before the carrier phase observable can be utilized as a range information its inherent integer cycle ambiguity must be resolved. The algorithms for ambiguity resolution and carrier phase positioning rely on the ambiguities being constant. Unfortunately, high dynamics, shadowing and multipath may cause cycle slips, i.e. jumps of the carrier phase observable by an integer multiple of wavelengths. Any cycle slip if remained undetected would deteriorate the high ranging and positioning accuracy. Therefore, a great number of algorithms and schemes have been developed in the past to detect and eventually repair cycle slips. All these methods have certain short-comings mainly due to unmodelled user dynamics or simultaneous cylce slips on both L1 and L2. These can be overcome by using an accurate integrated system consisting of an inertial measurement unit (IMU) and a differential GPS (Global Positioning System) sensor. Whenever there are reliable carrier phase positioning information the IMU error model is calibrated. The position of the then calibrated IMU with very good short-term accuracy is used to check for cycle slips the next time GPS carrier phase measurements become available. In case of cycle slip detection and repair, the affected carrier phase observable can still be used for positioning purposes. If cycle slips were detected but a correction was not possible then the carrier phase observable is excluded from navigation calculations. With this method the availability and reliability of cycle slip free carrier phase in formation is greatly enhanced which will be demonstrated in both driving and flight tests.
Published in:	Proceedings of the 2000 National Technical Meeting of The Institute of Navigation January 26 - 28, 2000 Pacific Hotel Disneyland Anaheim, CA
Pages:	134 - 144
Cite this article:	Altmayer, Christian, "Cycle Slip Detection and Correction by Means of Integrated Systems," Proceedings of the 2000 National Technical Meeting of The Institute of Navigation, Anaheim, CA, January 2000, pp. 134-144.
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