{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,11,10]],"date-time":"2025-11-10T13:52:44Z","timestamp":1762782764494,"version":"build-2065373602"},"reference-count":26,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2022,5,26]],"date-time":"2022-05-26T00:00:00Z","timestamp":1653523200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100011354","name":"State Key Laboratory of Geo-Information Engineering","doi-asserted-by":"publisher","award":["SKLGIE2019\u2013Z\u20131\u20131","41904030","2020JJ5706"],"award-info":[{"award-number":["SKLGIE2019\u2013Z\u20131\u20131","41904030","2020JJ5706"]}],"id":[{"id":"10.13039\/501100011354","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["SKLGIE2019\u2013Z\u20131\u20131","41904030","2020JJ5706"],"award-info":[{"award-number":["SKLGIE2019\u2013Z\u20131\u20131","41904030","2020JJ5706"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Natural Science Foundation of Hunan Province, China","award":["SKLGIE2019\u2013Z\u20131\u20131","41904030","2020JJ5706"],"award-info":[{"award-number":["SKLGIE2019\u2013Z\u20131\u20131","41904030","2020JJ5706"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Galileo satellites can broadcast signals on five frequencies, namely E1, E5A, E5B, E5 (A+B), and E6. The multi-frequency integration has become an emerging trend in Global Navigation Satellite System (GNSS) data processing. This study focused on the precise time transfer based on Galileo five-frequency uncombined precise point positioning (PPP), including the performance comparison of PPP time transfer with a priori and a posteriori weighting strategies, with different inter-frequency bias (IFB) dynamic models, and with the precise satellite products from different analysis centers, as well as the contribution of multi-frequency observations for time transfer. Compared with the a priori weighting strategy, the short-term frequency stability of time transfer adopting the Helmert variance component estimation method can be improved by 28.9\u201337.6% when the average time is shorter than 100 s. The effect of IFB dynamic models on Galileo five-frequency PPP time transfer is not obvious. When employing the post-processed precise satellite products from seven analysis centers, the accuracy of time transfer can be better than 0.1 ns, while an accuracy of 0.253 ns can be obtained in the real-time mode. At an average time of approximately 10,000 s, the post-processed time transfer with Galileo five-frequency PPP can provide a frequency stability of 3.283 \u00d7 10\u221214 to 3.459 \u00d7 10\u221214, while that in real-time mode can be 3.541 \u00d7 10\u221214. Compared with dual-frequency PPP results, the contribution of multi-frequency combination to the accuracy and frequency stability of time transfer is not significant, but multi-frequency PPP can achieve more reliable time transfer results when the signal quality is poor.<\/jats:p>","DOI":"10.3390\/rs14112538","type":"journal-article","created":{"date-parts":[[2022,5,31]],"date-time":"2022-05-31T00:25:12Z","timestamp":1653956712000},"page":"2538","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":8,"title":["Galileo Time Transfer with Five-Frequency Uncombined PPP: A Posteriori Weighting, Inter-Frequency Bias, Precise Products and Multi-Frequency Contribution"],"prefix":"10.3390","volume":"14","author":[{"given":"Zhehao","family":"Zhang","sequence":"first","affiliation":[{"name":"State Key Laboratory of Geo-Information Engineering, Xi\u2019an 710054, China"},{"name":"School of Geosciences and Info-Physics, Central South University, Changsha 410083, China"}]},{"given":"Lin","family":"Pan","sequence":"additional","affiliation":[{"name":"School of Geosciences and Info-Physics, Central South University, Changsha 410083, China"}]}],"member":"1968","published-online":{"date-parts":[[2022,5,26]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"108597","DOI":"10.1016\/j.measurement.2020.108597","article-title":"Research on Time and Frequency Transfer during PPP Convergence with Parameters Correlation Comparison","volume":"173","author":"Ouyang","year":"2021","journal-title":"Measurement"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"305","DOI":"10.1088\/0026-1394\/46\/3\/019","article-title":"Combination of TWSTFT and GNSS for Accurate UTC Time Transfer","volume":"46","author":"Jiang","year":"2009","journal-title":"Metrologia"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"165","DOI":"10.1007\/s10291-014-0377-5","article-title":"Monitoring of UTC(k)\u2019s Using PPP and IGS Real-Time Products","volume":"19","author":"Defraigne","year":"2015","journal-title":"GPS Solut."},{"key":"ref_4","first-page":"562878","article-title":"Precise Point Positioning for TAI Computation","volume":"2008","author":"Petit","year":"2008","journal-title":"Int. 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