Aided GPS Integer Ambiguity Resolution Using Low-cost Motion Sensors

Tashfeen B. Karamat, Mohamed M. Atia, Malek Karaim, Aboelmagd Noureldin

Peer Reviewed

Abstract:	Use of the carrier phase measurements in Global Positioning System (GPS) enables centimeter to millimeter level positioning accuracy. However, this is only possible when the Integer Ambiguities (IAs) are correctly resolved. In challenging GPS scenarios when fewer GPS satellites are visible, the Integer Ambiguity Resolution (IAR) takes longer time which affects continuity of precise positioning. In kinematic positioning, the Time-to-Fix Ambiguities (TTFA) is critical since IAR is frequently required as cycle-slips and satellite signal loss are common due to obstructions in urban canyons. Most of the previous works have utilized expensive high-end Inertial Measurement Units (IMUs) to aid GPS in IAR. This work investigates the use of reduced set of Micro-Electro-Mechanical Systems (MEMS)-based inertial sensors along with the vehicle’s speed measurements to help reduce TTFA. Double Difference (DD) GPS carrier phase and pseudorange measurements are integrated with other sensors’ measurements using an enhanced Extended Kalman Filter (EKF)-based estimator to obtain the Float Ambiguities (FAs). FAs and their Variance-Covariance Matrix (VCM) are used in Least Squares Ambiguity Decorrelation Adjustment (LAMBDA) method to fix FAs to integers. Due to the inclusion of inertial and odometery measurements, entities of VCM become smaller which translates into smaller search space for LAMBDA and faster resolution of ambiguities. The proposed method was tested on several real road trajectories and it performed 24% better than GPS-only algorithm for the case of 4 visible satellites. For 5 and 6 visible satellites, it performed 19% and 8% better than GP-S only algorithm respectively. For 7 and more satellites, both the algorithms resolved IAs instantaneously.
Published in:	Proceedings of the 28th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2015) September 14 - 18, 2015 Tampa Convention Center Tampa, Florida
Pages:	2548 - 2559
Cite this article:	Karamat, Tashfeen B., Atia, Mohamed M., Karaim, Malek, Noureldin, Aboelmagd, "Aided GPS Integer Ambiguity Resolution Using Low-cost Motion Sensors," Proceedings of the 28th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2015), Tampa, Florida, September 2015, pp. 2548-2559.
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