{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T03:32:53Z","timestamp":1760239973095,"version":"build-2065373602"},"reference-count":42,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2019,2,4]],"date-time":"2019-02-04T00:00:00Z","timestamp":1549238400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>The emergence of multiple global navigation satellite systems (multi-GNSS), including global positioning system (GPS), global navigation satellite system (GLONASS), Beidou navigation satellite system (BDS), and Galileo, brings not only great opportunities for real-time precise point positioning (PPP), but also challenges in quality control because of inevitable data anomalies. This research aims at achieving the real-time quality control of the multi-GNSS combined PPP using additional observations with opposite weight. A robust multiple-system combined PPP estimation is developed to simultaneously process observations from all the four GNSS systems as well as single, dual, or triple systems. The experiment indicates that the proposed quality control can effectively eliminate the influence of outliers on the single GPS and the multiple-system combined PPP. The analysis on the positioning accuracy and the convergence time of the proposed robust PPP is conducted based on one week\u2019s data from 32 globally distributed stations. The positioning root mean square (RMS) error of the quad-system combined PPP is 1.2 cm, 1.0 cm, and 3.0 cm in the east, north, and upward components, respectively, with the improvements of 62.5%, 63.0%, and 55.2% compared to those of single GPS. The average convergence time of the quad-system combined PPP in the horizontal and vertical components is 12.8 min and 12.2 min, respectively, while it is 26.5 min and 23.7 min when only using single-GPS PPP. The positioning performance of the GPS, GLONASS, and BDS (GRC) combination and the GPS, GLONASS, and Galileo (GRE) combination is comparable to the GPS, GLONASS, BDS and Galileo (GRCE) combination and it is better than that of the GPS, BDS, and Galileo (GCE) combination. Compared to GPS, the improvements of the positioning accuracy of the GPS and GLONASS (GR) combination, the GPS and Galileo (GE) combination, the GPS and BDS (GC) combination in the east component are 53.1%, 43.8%, and 40.6%, respectively, while they are 55.6%, 48.1%, and 40.7% in the north component, and 47.8%, 40.3%, and 34.3% in the upward component.<\/jats:p>","DOI":"10.3390\/rs11030311","type":"journal-article","created":{"date-parts":[[2019,2,5]],"date-time":"2019-02-05T11:31:07Z","timestamp":1549366267000},"page":"311","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["Multi-GNSS Combined Precise Point Positioning Using Additional Observations with Opposite Weight for Real-Time Quality Control"],"prefix":"10.3390","volume":"11","author":[{"given":"Wenju","family":"Fu","sequence":"first","affiliation":[{"name":"College of Geomatics, Xi\u2019an University of Science and Technology, Xi\u2019an 710054, China"},{"name":"College of Geology Engineering and Geomatic, Chang\u2019an University, Xi\u2019an 710054, China"},{"name":"German Research Centre for Geosciences (GFZ), Potsdam 14473, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Guanwen","family":"Huang","sequence":"additional","affiliation":[{"name":"College of Geology Engineering and Geomatic, Chang\u2019an University, Xi\u2019an 710054, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5553-948X","authenticated-orcid":false,"given":"Yuanxi","family":"Yang","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Geo-information Engineering, Xi\u2019an 710054, China"},{"name":"Xi\u2019an Research Institute of Surveying and Mapping, Xi\u2019an 710054, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Qin","family":"Zhang","sequence":"additional","affiliation":[{"name":"College of Geology Engineering and Geomatic, Chang\u2019an University, Xi\u2019an 710054, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Bobin","family":"Cui","sequence":"additional","affiliation":[{"name":"German Research Centre for Geosciences (GFZ), Potsdam 14473, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Maorong","family":"Ge","sequence":"additional","affiliation":[{"name":"German Research Centre for Geosciences (GFZ), Potsdam 14473, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Harald","family":"Schuh","sequence":"additional","affiliation":[{"name":"German Research Centre for Geosciences (GFZ), Potsdam 14473, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2019,2,4]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1251","DOI":"10.1007\/s10291-017-0610-0","article-title":"Robust combination of IGS analysis center GLONASS clocks","volume":"21","author":"Chen","year":"2017","journal-title":"GPS Solut."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"95","DOI":"10.1007\/s10291-013-0313-0","article-title":"Real-time clock offset prediction with an improved GPS satellite clocks model","volume":"18","author":"Huang","year":"2014","journal-title":"GPS Solut."},{"doi-asserted-by":"crossref","unstructured":"Huang, G.W., Cui, B.B., Zhang, Q., Fu, W.J., and Li, P.L. 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