• Journal of Advanced Navigation Technology
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• v.22 no.4
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• pp.271-278
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• 2018

For ionospheric correction of low earth orbiter (LEO) satellites using single frequency global navigation satellite system (GNSS) receiver, ionospheric scale factor should be applied to the ground-based ionosphere model. The ionospheric scale factor can be calculated by using a NeQuick model, which provides a three-dimensional ionospheric distribution. In this study, the ionospheric scale factor is calculated by using NeQuick G model during 2015, and it is compared with the scale factor computed from the combination of LEO satellite measurements and international GNSS service (IGS) global ionosphere map (GIM). The accuracy of the ionospheric delay calculated by the NeQuick G model and IGS GIM with NeQuick G scale factor is analyzed. In addition, ionospheric delay errors calculated by the NeQuick G model and IGS GIM with the NeQuick G scale factor are compared. The ionospheric delay error variations along to latitude and solar activity are also analyzed. The mean ionospheric scale factor from the NeQuick G model is 0.269 in 2015. The ionospheric delay error of IGS GIM with NeQuick G scale factor is 23.7% less than that of NeQuick G model.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.28 no.4
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• pp.413-420
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• 2010

The ionospheric delay is currently one of the most significant error sources in precise GNSS surveys. The users of single-frequency receivers should apply some kind of ionospheric correction algorithms to remove or model the ionospheric delay. For real-time correction of the ionospheric delay, one can use Klobuchar or NeQuick model provided by navigation messages of GPS and Galileo, respectively. We evaluated the performance of those models by comparing their effectiveness at different seasons and latitudes. For the first test, we computed the vertical total electron content (VTEC) at the permanent GPS site SUWN for four different seasons. As the second test, we picked three sites in Korea (CHLW, SUWN, JEJU) with high, medium, and low latitudes and evaluated the dependency of VTEC on the site latitude. Computed VTEC values were compared with those from the IRI model and Global Ionosphere Maps (GIM). The root-mean-square (RMS) differences of Klobuchar and NeQuick with respect to IRI and GIM were analyzed. As a result, without regard to season and latitude, the RMS differences of NeQuick models were smaller than that of Klobuchar by about 0.01~3.50 TECU.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2010.04a
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• pp.147-150
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• 2010

Ionopheric deley is the largest error sources in GNSS positining. The single frequency receiver user needs an ionospheric model like the Klobuchar model or NeQuick model to eliminate the ionospheric error. In this study we estimated VTEC(Vertical Total Electron Content) over DAEJ station using the two models in each season. We compared the results with Global Ionosphere Maps and International Reference Ionosphere model predictions. As a result, the NeQuick model was more accurate than Klobuchar model.

• Journal of Advanced Navigation Technology
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• v.21 no.5
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• pp.479-484
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• 2017

A Neustrelitz TEC model (NTCM) developed by Deutsches Zentrum $f{\ddot{u}}r$ Luft- und Raumfahrt (DLR) provides a better accuracy than the global positioning system (GPS) Klobuchar model for predicting ionospheric delay. The NTCM model accuracy is comparable to Galileo NeQuick model, and it has less computation time. The NTCM model uses F10.7 values as a parameter of solar activity function, while a NTCM-Broadcast (NTCM-BC) uses TEC values from a Klobuchar model. For this reason, a NTCM-BC model can be used for real-time ionosphere correction. In this paper, vertical ionospheric delay and GPS positioning errors in Korea by using a NTCM-BC ionosphere model from 2009 to 2014 are analyzed and compared with those of a Klobuchar model. In the 6-year statistics, the vertical ionospheric delay is reduced by 17.7 %, and horizontal and vertical positioning accuracies by the NTCM-BC model are improved by 25.6 % and 6.7 %, respectively, over the Klobuchar model.