{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,12,31]],"date-time":"2025-12-31T12:14:46Z","timestamp":1767183286976,"version":"build-2065373602"},"reference-count":31,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2024,4,25]],"date-time":"2024-04-25T00:00:00Z","timestamp":1714003200000},"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":["42304023","42304015","42274044","2022M723404","20XD1404500","BK20231087","SKLGED2024-3-7"],"award-info":[{"award-number":["42304023","42304015","42274044","2022M723404","20XD1404500","BK20231087","SKLGED2024-3-7"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100002858","name":"China Postdoctoral Science Foundation","doi-asserted-by":"publisher","award":["42304023","42304015","42274044","2022M723404","20XD1404500","BK20231087","SKLGED2024-3-7"],"award-info":[{"award-number":["42304023","42304015","42274044","2022M723404","20XD1404500","BK20231087","SKLGED2024-3-7"]}],"id":[{"id":"10.13039\/501100002858","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100012247","name":"Program of Shanghai Academic\/Technology Research Leader","doi-asserted-by":"publisher","award":["42304023","42304015","42274044","2022M723404","20XD1404500","BK20231087","SKLGED2024-3-7"],"award-info":[{"award-number":["42304023","42304015","42274044","2022M723404","20XD1404500","BK20231087","SKLGED2024-3-7"]}],"id":[{"id":"10.13039\/501100012247","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Jiangsu Province Natural Science Foundation of China","award":["42304023","42304015","42274044","2022M723404","20XD1404500","BK20231087","SKLGED2024-3-7"],"award-info":[{"award-number":["42304023","42304015","42274044","2022M723404","20XD1404500","BK20231087","SKLGED2024-3-7"]}]},{"name":"Open Research Foundation of the State Key Laboratory of Geodesy and Earth\u2019s Dynamics","award":["42304023","42304015","42274044","2022M723404","20XD1404500","BK20231087","SKLGED2024-3-7"],"award-info":[{"award-number":["42304023","42304015","42274044","2022M723404","20XD1404500","BK20231087","SKLGED2024-3-7"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>The multi-global navigation satellite system (GNSS) undifferenced and uncombined precise point positioning (UU-PPP), as a high-precision ionospheric observables extraction technology superior to the traditional carrier-to-code leveling (CCL) method, has received increasing attention. In previous research, only dual-frequency (DF) or multi-frequency (MF) observations are used to extract slant ionospheric delay with the UU-PPP. To reduce the cost of ionospheric modeling, the feasibility of extracting ionospheric observables from the multi-GNSS single-frequency (SF) UU-PPP was investigated in this study. Meanwhile, the between-satellite single-differenced (SD) method was applied to remove the effects of the receiver differential code bias (DCB) with short-term time-varying characteristics in regional ionospheric modeling. In the assessment of the regional real-time (RT) between-satellite SD ionospheric model, the internal accord accuracy of the SD ionospheric delay can be better than 0.5 TECU, and its external accord accuracy within 1.0 TECU is significantly superior to three global RT ionospheric models. With the introduction of the proposed SD ionospheric model into the multi-GNSS kinematic RT SF-PPP, the initialization speed of vertical positioning errors can be improved by 21.3% in comparison with the GRAPHIC (GRoup And PHase Ionospheric Correction) SF-PPP model. After reinitialization, both horizontal and vertical positioning errors of the SD ionospheric constrained (IC) SF-PPP can be maintained within 0.2 m. This proves that the proposed SDIC SF-PPP model can enhance the continuity and stability of kinematic positioning in the case of some GNSS signals missing or blocked. Compared with the GRAPHIC SF-PPP, the horizontal positioning accuracy of the SDIC SF-PPP in kinematic mode can be improved by 37.9%, but its vertical positioning accuracy may be decreased. Overall, the 3D positioning accuracy of the SD ionospheric-constrained RT SF-PPP can be better than 0.3 m.<\/jats:p>","DOI":"10.3390\/rs16091511","type":"journal-article","created":{"date-parts":[[2024,4,25]],"date-time":"2024-04-25T05:26:13Z","timestamp":1714022773000},"page":"1511","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["Regional Real-Time between-Satellite Single-Differenced Ionospheric Model Establishing by Multi-GNSS Single-Frequency Observations: Performance Evaluation and PPP Augmentation"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-4440-1263","authenticated-orcid":false,"given":"Ahao","family":"Wang","sequence":"first","affiliation":[{"name":"College of Geoscience and Surveying Engineering, China University of Mining and Technology-Beijing, Beijing 100083, China"}]},{"given":"Yize","family":"Zhang","sequence":"additional","affiliation":[{"name":"Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2899-7677","authenticated-orcid":false,"given":"Junping","family":"Chen","sequence":"additional","affiliation":[{"name":"Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030, China"},{"name":"School of Astronomy and Space Science, University of Chinese Academy of Sciences, Beijing 100049, China"}]},{"given":"Xuexi","family":"Liu","sequence":"additional","affiliation":[{"name":"School of Environment Science and Spatial Informatics, China University of Mining and Technology, Xuzhou 221116, China"}]},{"given":"Hu","family":"Wang","sequence":"additional","affiliation":[{"name":"Chinese Academy of Surveying & Mapping, Beijing 100036, China"}]}],"member":"1968","published-online":{"date-parts":[[2024,4,25]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"887","DOI":"10.1007\/s00190-011-0508-5","article-title":"The ionosphere: Effects, GPS modeling and the benefits for space geodetic techniques","volume":"85","author":"Juan","year":"2011","journal-title":"J. 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