Effect of Oscillator Quality on Ultra-Tight GPS/INS Aided Carrier Phase Tracking

Srinivas Bhaskar, James T. Curran, Gerard Lachapelle

Abstract:	Global Navigation Satellite Systems (GNSS) receivers used in applications which demand high accuracy are generally based on Real Time Kinematic (RTK) positioning. The positioning accuracy of such receivers primarily depends on the ability of the receiver to track the carrier phase of satellite signal. Unfortunately, from a tracking perspective, this parameter is the most sensitive to interference and attenuation. While the RTK based applications typically enjoy the full view of the sky most of the time, there are occasions when the satellite signals are obstructed due to foliage, high raised buildings, and other man-made structures. Under such operating conditions, maintaining phase lock can be a challenging task. Recent advances in the field of inertial navigation have shown that ultra-tight integration of Inertial Navigation System (INS) with a GNSS receiver can provide significant improvement in carrier phase tracking (Petovello et al 2007). This improvement, it appears, is limited by the quality of the receiver components. Specifically, it has been shown that, under weak signal conditions, the local oscillator is the main detriment for carrier phase tracking (O’Driscoll et al 2008). In this paper, the influence of the oscillator quality on carrier phase tracking performance is investigated. Particularly, the effects of acceleration sensitivity (or g-sensitivity) of the oscillator are examined in the context of pedestrian navigation. A method to compensate for the oscillator’s g-sensitivity, using information from Inertial Measurement Unit (IMU) is proposed and tested. The algorithm is validated using a high quality IMU and, subsequently, the relative performance of a MEMS grade sensor is assessed.
Published in:	Proceedings of the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2012) September 17 - 21, 2012 Nashville Convention Center, Nashville, Tennessee Nashville, TN
Pages:	56 - 66
Cite this article:	Bhaskar, Srinivas, Curran, James T., Lachapelle, Gerard, "Effect of Oscillator Quality on Ultra-Tight GPS/INS Aided Carrier Phase Tracking," Proceedings of the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2012), Nashville, TN, September 2012, pp. 56-66.
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