{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,17]],"date-time":"2026-01-17T07:15:27Z","timestamp":1768634127355,"version":"3.49.0"},"reference-count":45,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2017,3,9]],"date-time":"2017-03-09T00:00:00Z","timestamp":1489017600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJGI"],"abstract":"<jats:p>Although the Klobuchar model is widely used in single-frequency GPS receivers, it cannot effectively correct the ionospheric delay. The Klobuchar model sets the night ionospheric delay as a constant, i.e., it cannot reflect temporal changes at night. The observation data of seventeen International Global Navigation Satellite System Service (IGS) stations within and around China from 2011 provided by the IGS center are used in this study to calculate the Total Electron Content (TEC) values using the Klobuchar model and the dual-frequency model. The Holt\u2013Winters exponential smoothing model is used to forecast the error of the 7th day between the Klobuchar model and the dual-frequency model by using the error of the former six days. The forecast results are used to develop the sophisticated Klobuchar model when no epochs are missing, considering that certain reasons may result in some of the observation data being missing and weaken the relationship between each epoch in practical applications. We study the applicability of the sophisticated Klobuchar model when observation data are missing. This study deletes observation data of some epochs randomly and then calculates TEC values using the Klobuchar model. A cubic spline curve is used to restore the missing TEC values calculated in the Klobuchar mode. Finally, we develop the sophisticated Klobuchar model when N epochs are missing in China. The sophisticated Klobuchar model is compared with the dual-frequency model. The experimental results reveal the following: (1) the sophisticated Klobuchar model can correct the ionospheric delay more significantly than the Klobuchar model; (2) the sophisticated Klobuchar model can reflect the ionosphere temporal evolution, particularly at night, with the correct results increasing with increasing latitude; and (3) the sophisticated Klobuchar model can achieve remarkable correction results when N epochs are missing, with the correct results being nearly as good as that of the dual-frequency model when no epochs are missing.<\/jats:p>","DOI":"10.3390\/ijgi6030075","type":"journal-article","created":{"date-parts":[[2017,3,9]],"date-time":"2017-03-09T04:53:03Z","timestamp":1489035183000},"page":"75","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":16,"title":["Applicability Analysis of VTEC Derived from the Sophisticated Klobuchar Model in China"],"prefix":"10.3390","volume":"6","author":[{"given":"Jun","family":"Chen","sequence":"first","affiliation":[{"name":"College of Geomatics and Geoinformation, Guilin University of Technology, Guilin 541004, China"},{"name":"Guangxi Key Laboratory of Spatial Information and Geomatics, Guilin 541004, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Liangke","family":"Huang","sequence":"additional","affiliation":[{"name":"College of Geomatics and Geoinformation, Guilin University of Technology, Guilin 541004, China"},{"name":"Guangxi Key Laboratory of Spatial Information and Geomatics, Guilin 541004, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Lilong","family":"Liu","sequence":"additional","affiliation":[{"name":"College of Geomatics and Geoinformation, Guilin University of Technology, Guilin 541004, China"},{"name":"Guangxi Key Laboratory of Spatial Information and Geomatics, Guilin 541004, China"},{"name":"College of Resources and Environment, Qinzhou University, Qinzhou 535000, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Pituan","family":"Wu","sequence":"additional","affiliation":[{"name":"College of Geomatics and Geoinformation, Guilin University of Technology, Guilin 541004, China"},{"name":"Guangxi Key Laboratory of Spatial Information and Geomatics, Guilin 541004, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Xuyuan","family":"Qin","sequence":"additional","affiliation":[{"name":"College of Geomatics and Geoinformation, Guilin University of Technology, Guilin 541004, China"},{"name":"Guangxi Key Laboratory of Spatial Information and Geomatics, Guilin 541004, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2017,3,9]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"649","DOI":"10.1007\/s10291-014-0419-z","article-title":"Modeling regional ionospheric delay with ground-based BeiDou and GPS observations in China","volume":"19","author":"Zhang","year":"2015","journal-title":"GPS Solut."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1007\/s11432-015-5399-2","article-title":"A regional ionospheric TEC mapping technique over China and adjacent areas: GNSS data processing and DINEOF analysis","volume":"58","author":"Ercha","year":"2015","journal-title":"Sci. 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