Workshop 2018
Jiang Guo - Towards instantaneous PPP initialization in case of triple-frequency multi-GNSS data - October 29, 2018 • 600 Views
Fast convergence of precise point positioning (PPP) has confused the GNSS community for several years. Even though multi-GNSS ambiguity resolution performs as a quite validate method to relieve this problem, the initialization time of PPP is still unacceptable for some real-time applications. It is however expected that this difficult situation can be relieved or even resolved using triple-frequency GNSS data. We therefore propose an approach where raw triple-frequency GPS/BeiDou/Galileo/QZSS (Quasi-zenith satellite system) observations are directly injected into PPP, whereas their ambiguities are mapped into the extra-wide-lane, wide-lane and narrow-lane combinations for integer-cycle resolution at a single station (i.e., PPP-AR). Once both extra-wide-lane and wide-lane ambiguities are fixed to integers, the resulting unambiguous (extra-) wide-lane carrier-phase can potentially outweigh raw pseudorange to improve the convergence efficiency of positions and narrow-lane ambiguities. We used 31 days of triple-frequency multi-GNSS data from 76 stations over the Asia-Oceania regions to test real-time PPP-AR, from which we found that the positioning accuracy for the first ten minutes of every hourly result could be improved by about 50% from 0.23, 0.18 and 0.43 m to 0.12, 0.08 and 0.27 m for the east, north and up components, respectively, with (extra-)wide-lane ambiguity fixed successfully in triple-frequency PPP. Consequently, 48.1% of triple-frequency PPP solutions could be initialized successfully with narrow-lane ambiguities resolved within 2 minutes, in contrast to only 26.4% in case of dual-frequency PPP. Finally, the average time to achieve triple-frequency PPP-AR is 6.1 minutes whereas 9.2 minutes for dual-frequency PPP-AR. It should be noted particularly that the more satellites contribute to triple-frequency PPP-AR, the faster the initializations will be; as a typical example, the mean initialization period declined to only 2.7 minutes in case of 20–21 satellites. It is very promising that PPP-AR will bereliably initialized within only a few minutes of epochs when all GPS, BeiDou, Galileo and QZSS constellations emitting triple-frequency signals are complete in the near future.

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