Abstract
The new generations of global navigation satellite system (GNSS) space vehicles can transmit three or more frequency signals. Multi-frequency observations bring a significant improvement to precise point positioning ambiguity resolution (PPP AR). However, the multi-frequency satellite code and phase biases need to be properly handled before conducting PPP AR. The traditional satellite bias correction methods, for example, the commonly used differential code biases (DCB), are limited to the dual-frequency ionosphere-free (IF) case and become more and more difficult to extend to multi-GNSS and multi-frequency cases. In this contribution, we propose the observable-specific signal bias (OSB) correction method for un-differenced and uncombined (UDUC) PPP AR. The OSB correction method, which includes observable-specific satellite code and phase bias correction, can directly apply kinds of OSBs to GNSS original observation data, thus, it is more appropriate for multi-GNSS and multi-frequency cases. In order to verify the performance of multi-frequency UDUC-PPP AR based on the OSB correction method, triple-frequency GPS observation data provided by 142 Multi-GNSS Experiment (MGEX) stations were used to estimate observable-specific satellite phase biases at the PPP service end and some of them were also used to conduct AR at the PPP user end. The experiment results showed: the averaged time-to-first-fix (TTFF) of triple-frequency GPS kinematic UDUC-PPP AR with observable-specific satellite code bias (SCB) corrections could reach about 22 min with about 29% improvement, compared with that without observable-specific SCB corrections; TTFF of triple-frequency static UDUC-PPP AR with observable-specific phase-specific time-variant inter-frequency clock bias (IFCB) corrections took about 15.6 min with about 64.3% improvement, compared with that without observable-specific IFCB corrections.
Highlights
As known to all, the new generations of global navigation satellite system (GNSS) space vehicles can transmit three or more frequency signals
We investigate the performance of triple-frequency global positioning system (GPS) UDCU-point positioning ambiguity resolution (PPP AR) with observable-specific satellite code and phase biases
In order to conveniently conduct multi-frequency and multi-GNSS un-differenced and uncombined (UDUC)-precise point positioning (PPP) AR, we proposed a method to uniformly correct time-invariant and time-variant satellite biases and designed a corresponding file format of bias corrections
Summary
The new generations of global navigation satellite system (GNSS) space vehicles can transmit three or more frequency signals. It is essential that the code and phase biases on each frequency are properly handled as a prerequisite of conducting multi-frequency PPP AR. This is mainly because the code biases could reduce the accuracy of pseudo-range observations and the phase biases could affect carrier-phase observations and destroy the un-difference integer ambiguity. Correct calibration of these biases could undoubtedly improve the accuracy of observation data as well as restore the un-difference integer ambiguity. The current study of the code and phase biases for PPP AR focuses on the satellite code and phase biases
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