Integrity monitoring-based ratio test for GNSS integer ambiguity validation

The combination of multiple global navigation satellite systems (GNSSs) is able to improve the accuracy and reliability, which is beneficial for navigation in safety–critical applications. Due to the relatively low accuracy of pseudorange observations, the single-epoch GNSS real-time kinematic (RTK) using phase observations can be utilized to achieve centimeter accuracy positioning instantaneously. Since the traditional ratio tests for ambiguity validation are not reliable in the presence of biases, it is therefore difficult for the single-epoch RTK to achieve high precision and high reliability, simultaneously. Instead of using an empirical constant detection threshold or a fixed failure/success rate requirement in the ratio tests for ambiguity validation, we propose an integrity monitoring-based ratio test (IM-RT). It uses the ambiguity protection level to control the false alarm and missed detection errors. The performance of the proposed method is tested by using simulated and real-world data. The simulation results show that the IM-RT can obtain an optimal balance between the false alarm and missed detection performance. The experiments from kinematic real-world data indicate that the IM-RT improves the positioning accuracy by over 10 cm and enhances the continuity by 11 %, when compared with the fixed detection threshold-based ratio test.