Abstract
We investigate the estimation of the fractional cycle biases (FCBs) for GPS triple-frequency uncombined precise point positioning (PPP) with ambiguity resolution (AR) based on the IGS ultra-rapid predicted (IGU) orbits. The impact of the IGU orbit errors on the performance of GPS triple-frequency PPP AR is also assessed. The extra-wide-lane (EWL), wide-lane (WL) and narrow-lane (NL) FCBs are generated with the single difference (SD) between satellites model using the global reference stations based on the IGU orbits. For comparison purposes, the EWL, WL and NL FCBs based on the IGS final precise (IGF) orbits are estimated. Each of the EWL, WL and NL FCBs based on IGF and IGU orbits are converted to the uncombined FCBs to implement the static and kinematic triple-frequency PPP AR. Due to the short wavelengths of NL ambiguities, the IGU orbit errors significantly impact the precision and stability of NL FCBs. An average STD of 0.033 cycles is achieved for the NL FCBs based on IGF orbits, while the value of the NL FCBs based on IGU orbits is 0.133 cycles. In contrast, the EWL and WL FCBs generated based on IGU orbits have comparable precision and stability to those generated based on IGF orbits. The use of IGU orbits results in an increased time-to-first-fix (TTFF) and lower fixing rates compared to the use of IGF orbits. Average TTFFs of 23.3 min (static) and 31.1 min (kinematic) and fixing rates of 98.1% (static) and 97.4% (kinematic) are achieved for the triple-frequency PPP AR based on IGF orbits. The average TTFFs increase to 27.0 min (static) and 37.9 min (kinematic) with fixing rates of 97.0% (static) and 96.3% (kinematic) based on the IGU orbits. The convergence times and positioning accuracy of PPP and PPP AR based on IGU orbits are slightly worse than those based on IGF orbits. Additionally, limited by the number of satellites transmitting three frequency signals, the introduction of the third frequency, L5, has a marginal impact on the performance of PPP and PPP AR. The GPS triple-frequency PPP AR performance is expected to improve with the deployment of new-generation satellites capable of transmitting the L5 signal.
Highlights
The precision and stability of the EWL, WL and NL fractional cycle biases (FCBs) as well as the performance of GPS triple-frequency precise point positioning (PPP) and PPP ambiguity resolution (AR) based on International GNSS service (IGS) final precise (IGF) and IGS ultra-rapid predicted (IGU) orbits are investigated and compared
To investigate the impact of the IGU orbit errors on the GPS triple-frequency uncombined PPP AR performance, the EWL, WL and NL FCBs of GPS satellites were generated with the single difference (SD) model using global reference stations based on the IGU orbits
They were compared with the EWL, WL and NL FCBs estimates based on IGF orbits in terms of precision and stability for the first time
Summary
With the modernization of GPS and GLONASS as well as the deployment completion of Galileo and BDS-3, increasing numbers of satellites are transmitting beyond two signals for positioning and location services. For multi-frequency precise point positioning (PPP), more wide-lane (WL) ambiguities with long wavelengths can be formed and fixed instantaneously [1]. This makes instantaneous decimeter to centimeter-level positioning accuracy obtainable even only by fixing the WL ambiguities for multi-frequency and multiGNSS PPP [2]. Fast WL ambiguity resolution (AR) can accelerate the narrow-lane
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