Robust Single Antenna INS Initialization for Low Dynamic Applications

Pierre Bénet, Mourad Saidani, Alexis Guinamard

Peer Reviewed

Abstract: When coupling inertial sensors with GNSS, a key to enable robust navigation is to use reliable initialization methods. While it is straightforward to retrieve position and velocity from a standalone GNSS receiver, the attitude can be more challenging to initialize. Several methods for initializing this attitude are available in the literature. However, they all have their limitations. The process of finding the initial attitude is also referred to as the alignment. • Course Alignment requires the carrier to go on a straight line with a significant velocity and with no lateral velocity. When the carrier is a car, the condition is easily met. However, for a plane or a boat, the wind or the current can break the assumption of no lateral velocity. Hence this initialization method is not recommended for boats or planes. It is also not recommended for pedestrian applications which can move sidewards or backward, and which exhibit very low velocity. Other applications like UAVs or Helicopters can move in all directions, making this procedure unsafe. • Magnetic alignment which uses a magnetic compass can provide the initial attitude. this system requires a dedicated calibration procedure and is easily disturbed by surrounding metal objects. • Gyro-compassing is the process of detecting the earth rotation, thus deducing the attitude of the system. However, detecting the rotation of the earth requires an expensive high performance gyrometer. • Dual-antenna alignment requires two antennas on the carrier which must be separated enough. The constraint on the separation of the two antenna yields a more complex setup and is cumbersome on small carriers such as pedestrians. More generally, many attempts have been performed to overcome these limitations and provide a free kinematic alignment process. But they usually require significant dynamics and are not suitable for pedestrian applications. We developed an optimization-based solution that overcomes these problems. In particular, it solves initialization in the very difficult scenario of pedestrian single antenna with single point GNSS with MEMS gyrometer. Typical performance on a 10°/h grade gyrometer on a pedestrian yields 1° heading uncertainty within 15s of initialization time. SBG systems has developed this initialization algorithm (patent pending) to make pedestrian mono-antenna inertial-GNSS coupling and tight-coupling possible. Whereas it was not possible before with SBG post-processing software, it has been very recently integrated into our post-processing software Qinertia 4.0. It is also planned to make it available as a real-time initialization procedure running directly on the INS. Our algorithm has been tested in many scenarios with different carriers such as pedestrian or automotive. We will present the details of this algorithm and the detailed analysis of its performance in this paper.
Published in: Proceedings of the 2024 International Technical Meeting of The Institute of Navigation
January 23 - 25, 2024
Hyatt Regency Long Beach
Long Beach, California
Pages: 1021 - 1032
Cite this article: Bénet, Pierre, Saidani, Mourad, Guinamard, Alexis, "Robust Single Antenna INS Initialization for Low Dynamic Applications," Proceedings of the 2024 International Technical Meeting of The Institute of Navigation, Long Beach, California, January 2024, pp. 1021-1032.
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