{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,1]],"date-time":"2026-06-01T13:47:47Z","timestamp":1780321667192,"version":"3.54.1"},"reference-count":57,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2018,2,22]],"date-time":"2018-02-22T00:00:00Z","timestamp":1519257600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["41504006"],"award-info":[{"award-number":["41504006"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["41674034"],"award-info":[{"award-number":["41674034"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>The carrier-phase (CP) technique based on the Global Navigation Satellite System (GNSS) has proved to be a useful spatial tool for remote and precise time transfer. In order to improve the robustness and stability of the time transfer solution for a time link, a new CP approach based on a combination of GPS, BeiDou (BDS), and Galileo satellite systems is proposed in this study. The mathematical model for the obtained unique time transfer solution is discussed. Three GNSS stations that can track GPS, BeiDou, and Galileo satellites were used, and two time links are established to assess the performance of the approach. Multi-GNSS time transfer outperforms single GNSS by increasing the number of available satellites and improving the time dilution of precision. For the long time link, with a geodetic distance of 7537.5 km, the RMS value of the combined multi-system solution improves by 18.8%, 59.4%, and 35.0% compared to GPS-only, BDS-only, and Galileo-only, respectively. The average frequency stability improves by 12.9%, 62.3%, and 36.0%, respectively. For the short time link, with a geodetic distance of 4.7 m, the improvement after combining the three GNSSs is 6.7% for GPS-only, 52.6% for BDS-only, and 38.2% for Galileo-only.<\/jats:p>","DOI":"10.3390\/rs10020324","type":"journal-article","created":{"date-parts":[[2018,2,22]],"date-time":"2018-02-22T07:05:41Z","timestamp":1519283141000},"page":"324","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":61,"title":["Combining GPS, BeiDou, and Galileo Satellite Systems for Time and Frequency Transfer Based on Carrier Phase Observations"],"prefix":"10.3390","volume":"10","author":[{"given":"Pengfei","family":"Zhang","sequence":"first","affiliation":[{"name":"National Time Service Center, Chinese Academy of Sciences, Shu Yuan Road, Xi\u2019an 710600, China"},{"name":"Key Laboratory of Time and Frequency Primary Standards, Chinese Academy of Sciences, Xi\u2019an 710600, China"},{"name":"University of Chinese Academy of Sciences, Yu Quan Road, Beijing 100049, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Rui","family":"Tu","sequence":"additional","affiliation":[{"name":"National Time Service Center, Chinese Academy of Sciences, Shu Yuan Road, Xi\u2019an 710600, China"},{"name":"University of Chinese Academy of Sciences, Yu Quan Road, Beijing 100049, China"},{"name":"Key Laboratory of Precision Navigation Positioning and Timing Technology, Chinese Academy of Sciences, Xi\u2019an 710600, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Rui","family":"Zhang","sequence":"additional","affiliation":[{"name":"National Time Service Center, Chinese Academy of Sciences, Shu Yuan Road, Xi\u2019an 710600, China"},{"name":"Key Laboratory of Precision Navigation Positioning and Timing Technology, Chinese Academy of Sciences, Xi\u2019an 710600, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yuping","family":"Gao","sequence":"additional","affiliation":[{"name":"National Time Service Center, Chinese Academy of Sciences, Shu Yuan Road, Xi\u2019an 710600, China"},{"name":"Key Laboratory of Time and Frequency Primary Standards, Chinese Academy of Sciences, Xi\u2019an 710600, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hongbin","family":"Cai","sequence":"additional","affiliation":[{"name":"National Time Service Center, Chinese Academy of Sciences, Shu Yuan Road, Xi\u2019an 710600, China"},{"name":"Key Laboratory of Time and Frequency Primary Standards, Chinese Academy of Sciences, Xi\u2019an 710600, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2018,2,22]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Allan, D.W., and Weiss, M. 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