Rapid Initial Heading Alignment Using Single-Antenna GNSS and a Low-Grade IMU

For the integrated system incorporating a low-cost inertial measurement unit (IMU) and global navigation satellite system (GNSS), rapid and accurate initial heading alignment is still a significant challenge, especially for marine applications in challenging ocean conditions. To overcome this difficulty, we propose an in-motion coarse heading alignment method using single-antenna GNSS and a low-grade IMU based on the basic principle of trajectory similarity. The heading angle is determined by dead reckoning (DR)-derived trajectory and GNSS-derived trajectory using gyro measurements and GNSS positioning solutions. The proposed alignment method can be implemented in real-time and the alignment period is just 1s, which indicates that the method could continuously output heading when the carrier is in motion. Therefore, the continuous heading output calculated by the proposed algorithm can be applied to the state and fault detection of the carrier. Experimental results show that the heading could be determined with an accuracy of 0.48°, 3.14°, and 2.43° at a 95% confidence level for the land vehicle, unmanned surface vessel (USV), and unmanned underwater vehicle (UUV) tests, respectively. Besides, the RMS of the alignment errors calculated by our method reaches 0.20°, 1.42°, and 1.22° for the land vehicle, USV, and UUV tests, respectively.