Accurate In-Motion Initial Heading Alignment for Underwater Robots Using a Basis of the Initial Position-Error Space

Accurate initial heading alignment is crucial for autonomous underwater vehicles (AUVs) relying on dead-reckoning (DR) navigation. The multiple GNSS position-based alignment (MGPA) method, using standard point positioning (SPP) GNSS, is an applicable approach in marine environments due to its standalone nature. However, the performance of this method is directly degraded by the inherent error in the initial position, which can be relatively large due to the use of SPP. Therefore, this paper proposes a novel iterative method that estimates and corrects errors in both initial heading and position. The core of the method is a decomposition of the coupled 2D optimization problem into two 1D optimizations by identifying an orthogonal correction basis. The effectiveness of the proposed method is validated through at-sea experiments with an AUV. Experimental results demonstrate that the proposed method corrects the initial position error and achieves improved alignment, enhancing DR navigation accuracy.