Evolution of orbit and clock quality for real-time multi-GNSS solutions
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ORIGINAL ARTICLE
Evolution of orbit and clock quality for real‑time multi‑GNSS solutions Kamil Kazmierski1 · Radoslaw Zajdel1 · Krzysztof Sośnica1 Received: 17 March 2020 / Accepted: 14 August 2020 © The Author(s) 2020
Abstract High-quality satellite orbits and clocks are necessary for multi-GNSS precise point positioning and timing. In undifferenced GNSS solutions, the quality of orbit and clock products significantly influences the resulting position accuracy; therefore, for precise positioning in real time, the corrections for orbits and clocks are generated and distributed to users. In this research, we assess the quality and the availability of real-time CNES orbits and clocks for GPS, GLONASS, Galileo, and BeiDou-2 separated by satellite blocks and types, as well as the product quality changes over time. We calculate the signal-in-space ranging error (SISRE) as the main orbit and clock quality indicator. Moreover, we employ independent orbit validation based on satellite laser ranging. We found that the most accurate orbits are currently available for GPS. However, Galileo utmost stable atomic clocks compensate for systematic errors in Galileo orbits. As a result, the SISRE for Galileo is lower than that for GPS, equaling 1.6 and 2.3 cm for Galileo and GPS, respectively. The GLONASS satellites, despite the high quality of their orbits, are characterized by poor quality of clocks, and together with BeiDou-2 in medium and geosynchronous inclined orbits, are characterized by SISRE of 4–6 cm. BeiDou-2 in geostationary orbits is characterized by large orbital errors and the lowest availability of real-time orbit and clock corrections due to a large number of satellite maneuvers. The quality of GNSS orbit and clock corrections changes over time and depends on satellite type, block, orbit characteristics, onboard atomic clock, and the sun elevation above the orbital plane. Keywords Signal-in-space range error · GNSS orbits and clocks · Real-time positioning · Multi-GNSS · PPP
Introduction The precise, highly accurate orbit and clock products, which support all global navigation satellite systems (GNSS), including GPS, GLONASS, Galileo, and BeiDou, are becoming more accessible to all users that expect accurate position, navigation, and timing services. The GNSS community owes that to the International GNSS Service (IGS) Multi-GNSS Pilot Project (MGEX), which has been providing multi-GNSS products for almost ten years (Montenbruck et al. 2017). Thanks to MGEX, most of the applications of multi-GNSS data, such as kinematic or static positioning, navigation, and timing, are nowadays possible. However, due to the delay of approximately 14 days in the final product availability, there is a necessity to provide other products for * Kamil Kazmierski [email protected] 1
Institute of Geodesy and Geoinformatics, Wrocław University of Environmental and Life Sciences, Grunwaldzka 53, 50‑357 Wrocław, Poland
real-time (RT) users. One of the possibilities is to transmit precise corrections via the Internet
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