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Galileo supports global precise point positioning (PPP) service by delivering precise products via satellites, which is known as high accuracy service (HAS). To improve reception efficiency, the Galileo HAS employs a high-parity vertical reed-solomon encoding scheme, increasing the complexity of HAS corrections recovery. To promote research and application of the HAS, an open-source C/C + + decoding package, HASPPP, has been developed for seamless embedding into the prevalent C/C++-based software, such as RTKLIB. HASPPP provides interfaces for effortless decoding support of raw HAS binary data from various manufacturers. The HASPPP manual offers code analysis along with simple to complex examples to aid users in swiftly mastering decoding. HASPPP has undergone rigorous validation of its decoding accuracy and reliability. [ABSTRACT FROM AUTHOR]

The Beidou-3 system (BDS-3) satellites are deployed, equipped with an inter-satellite link (ISL) payload, so that the satellite–satellite or satellite-ground time synchronization is available. The satellite-ground link (GSL) can be used in conjunction with the ISL if proper attention is paid to all corrections and the biases are fitted. We execute methods to synchronize the clocks of BDS-3 satellites to an accurate reference clock on the ground, by estimating relative clock offsets obtained via Ka-band GSL observations. We solve for the relative biases using the closure properties of the redundant biases and the Ka-band (Ka-mode) satellite-ground two-way data. We find the biases, relative to the GSL hardware delay, are relatively stable in the short term. This makes it feasible to estimate them as a constant every few hours, and the standard deviation of the hardware delay estimations within 24 h is slightly less than 0.7 ns. The frequency stability of Ka-mode estimated clock offset shows a negative short-term performance because of the dominant effect of the white phase noise in the relative clock offsets from the Ka-mode, but the long-term performance seems to be improved to a higher level. The time synchronization accuracy of Ka-mode is proven to be better than 0.3 ns (RMS), whereas the accuracy for the high-orbit satellite is slightly worse. [ABSTRACT FROM AUTHOR]

Based on the batch expectation–maximization (EM) and recursive least-squares algorithms, we develop a new recursive variance components estimation (Recursive-VCE) algorithm that applies a Kalman filter and validates it by a simulated kinematic precise point positioning (PPP) experiment and a PPP test on real-world data. The Recursive-VCE algorithm processes the observations in an epoch-by-epoch or a group-by-group manner. Once new observations are obtained, it updates the estimates of the variance components in a recursive way or on the fly. Therefore, it does not require significant computing resources to store sufficiently large training datasets. The resulting algorithm is simple and able to be easily adapted to determine time-varying behaviours and is shown to converge faster than the batch EM algorithm because the EM algorithm updates the parameters only once after dealing with all the data. Hence, it is a good complement to other batch VCE methods, and its application in real-time data processing is promising. [ABSTRACT FROM AUTHOR]