Constrained Wrapped Least Squares: A Tool for High-Accuracy GNSS Attitude Determination

Attitude determination is a popular application of global navigation satellite systems (GNSS). Many methods have been developed to solve the attitude determination problem with different performance offerings. We develop a constrained wrapped least-squares (C-WLS) method for high-accuracy attitude determination. This approach is built on an optimization model that leverages prior information related to the antenna array and the integer nature of the carrier-phase ambiguities in an innovative way. The proposed approach adopts an efficient search strategy to estimate the vehicle's attitude parameters using ambiguous carrier-phase observations directly, without requiring prior carrier-phase ambiguity fixing. The performance of the proposed method is evaluated via simulations and experimentally utilizing data collected using multiple GNSS receivers. The simulation and experimental results demonstrate excellent performance, with the proposed method outperforming the ambiguity function method (AFM), the constrained least-squares ambiguity Decorrelation (LAMBDA) method, and multivariate constrained LAMBDA methods, three prominent attitude determination algorithms.