MULTI-GNSS receivers/IMU system aimed at the design of a heading-constrained tightly-coupled algorithm

This paper presents the design of a truly low-cost multi-GNSS receivers /IMU navigation system that exploits the benefits of GNSS technology in attitude determination. The sensor package of the system consists of 4 single chipset receivers, 4 antennas, and one low grade MEMS IMU. Both parts, the GNSS and the IMU ones, are integrated by following a heading-constrained Tightly-Coupled approach, where inertial and GNSS raw measurements as well as GNSS computed heading are blended into an Extended Kalman Filter. To compute the attitude solution based on GNSS carrier phase measurements an integer ambiguity resolution algorithm has been developed, which takes advantage of the a priori solution of the EKF to reduce the search space and to provide an on-the-fly solution. The heading-constrained Tightly-Coupled approach followed in this paper has shown superior attitude accuracies when compared to the regular Tightly-Coupled implementation.