Ionosphere-weighted post-processing kinematic for airborne positioning with refined modeling of receiver phase biases and tropospheric zenith wet delays

The application of the global navigation satellite system (GNSS) in aviation effectively meets the requirements of aircraft location-based services. However, the GNSS application in airborne surveys mostly follows the land survey method, which ignores the particularity of the airborne flight operations, such as the rapid change of altitude difference. The present study contributes to this research trend by constructing a suitable positioning model for airborne kinematic precise positioning and analyzing the variation characteristics of receiver phase biases (RPBs) and tropospheric zenith wet delays (ZWDs) to explore their impact on airborne positioning. The ionosphere-weighted post-processing kinematic (PPK) model for long-distance high-altitude positioning is constructed by adding the between-station single-differenced ionospheric pseudo-observations. Aside from these, the correlation between the characteristics of RPBs, ZWDs, and environmental factors (temperature, vapor pressure) is analyzed and the kinematic constraint of the ionosphere-weighted PPK model on RPBs and ZWDs is adjusted based on their true variations. The results show that under the condition of large altitude differences, temperature-sensitive RPBs and ZWDs significantly impact positioning. Furthermore, pre-calibrating RPBs and ZWDs can significantly improve the ambiguity success rate and positioning performance. Based on the bias-calibrated ionosphere-weighted PPK model, the fixed solutions difference of the two common-antenna moving stations carried by the manned aircraft is stable for the positioning results of the two flight experiments. The 3-dimensional root-mean-square (3D-RMS) values are 1.4 cm and 0.5 cm, with 82% and 99% ambiguity success ratios.