GPS/BDS Dual-antenna Attitude Determination with Baseline-length Constrained Ambiguity Resolution: Method and Performance Evaluation

Attitude determination using Global Navigation Satellite System (GNSS) has the characteristics of low cost, zero drift and all-weather. It has important application value in the fields of motion carrier navigation, airborne/shipborne mapping and rotational seismology. The key problem of GNSS attitude determination is the integer ambiguity resolution. Due to the influence of GNSS observation noise and environment, the ambiguity fixing rate and attitude accuracy sometimes can’t meet the needs of practical application. In this paper, we present the mathematical model for GNSS dual-antenna attitude determination augmented by baseline-length constrained ambiguity resolution. The baseline-length constraint is added to the parameter estimation as pseudo-observations through Kalman filter. To investigate the ambiguity resolution performance and accuracy of baseline-length constrained attitude determination, we carry out static and vehicle-based dynamic experiments with single and combined GPS/BDS systems. The experimental results prove that the baseline-length constraint takes effect under different elevation mask angles and systems. The best improvement is achieved by the GPS single system with the elevation mask angle of 40°, where the ambiguity fixing rate is increased from 59% to 84%, and 42% to 74% in the static and dynamic experiments, respectively. In BDS and GPS/BDS experiments, the improvement of ambiguity fixing rate is not significant, but the ratio values are largely increased and the accuracy maintains a high level. In the static experiment with the baseline length of 7.9 m, the accuracies reach 0.01° and 0.03° for yaw and pitch angles, respectively. Our results show that GNSS attitude determination with baseline-length constraint can significantly improve the ambiguity fixing rate and attitude accuracy, which is of great significance to expand the application of GNSS attitude determination in navigation, surveying and mapping, and geoscience studies.