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GPS Solutions

, 22:2 | Cite as

Influence of spatial gradients on ionospheric mapping using thin layer models

  • Hu Jiang
  • Zemin Wang
  • Jiachun An
  • Jingbin Liu
  • Ningbo Wang
  • Hang Li
Original Article

Abstract

This study provides information about the influence of various ionospheric spatial gradients on the thin layer ionospheric model (TLIM). Particular attention is paid to the errors caused by the slant total electron content (sTEC) when converted to the vertical total electron content (vTEC) by an elevation-dependent mapping function (MF), ignoring the satellite azimuth. We quantify the influence of the spatial gradient on ionospheric mapping using globally distributed GNSS measurements and the NeQuick2 ionospheric electron density model. The ionospheric mapping errors (IME) were confirmed using GNSS measurements that were observed for different solar activity conditions. It was found that the IME in the low latitudes were significantly higher than those at other latitudes, and the high-latitude region IME were more pronounced than those of the mid-latitude regions. A comprehensive simulation analysis based on the NeQuick2 model was conducted for different azimuth angles and geographical locations. It was found that the vTEC converted by the MF is smaller than the real value of vTEC in different spatial directions. The IME in the north-to-south direction were much higher than those in the east-to-west direction and were symmetrical north–south about the geomagnetic equator. The values of the IME had obviously seasonal variation characteristics: The IME in the spring and autumn were significantly higher than those in the winter and summer; however, in the low latitudes, the IME were abnormal and had larger values. There is an interesting phenomenon wherein the IME were symmetrical about the azimuth of 180°, and the value of the IME was less than 1 TECu when the satellite elevation was up to 50°. From the global perspective, when the thin layer height is at 400 km, the IME were relatively minimal. In addition, the modified single-layer model (MSLM) and Ou (Ou J) segmented mapping functions outperformed other mapping functions at low satellite elevations; however, when the elevation angle was increased to approximately 40°, the differences of the different MFs were small.

Keywords

Thin layer ionospheric model (TLIM) Total electron content (TEC) Ionosphere mapping error (IME) GPS NeQuick2 model 

Notes

Acknowledgments

The authors would like to acknowledge the Crustal Dynamics Data Information System (CDDIS) of the International GNSS Services (IGS) for providing access to the GPS observation data. We would also like to acknowledge the International Center for Theoretical Physics (ICTP) for providing the NeQuick2 sources. This research was supported by the Natural Science Funds of China (Nos. 41231064, 41776195, 41531069, 41174029 and 41474029) and the National Key Research Development Program of China with project No. 2016YFB0502204.

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Copyright information

© Springer-Verlag GmbH Germany 2017

Authors and Affiliations

  1. 1.Chinese Antarctic Center of Surveying and MappingWuhan UniversityWuhanChina
  2. 2.Collaborative Innovation Center for Territorial Sovereignty and Maritime RightsWuhan UniversityWuhanChina
  3. 3.State Key Laboratory of Information Engineering in Surveying, Mapping and Remote SensingWuhan UniversityWuhanChina
  4. 4.Collaborative Innovation Center of Geospatial TechnologyWuhan UniversityWuhanChina
  5. 5.Department of Remote Sensing and PhotogrammetryFinnish Geospatial Research InstituteMasalaFinland
  6. 6.Academy of Opto-ElectronicsChinese Academy of SciencesBeijingChina

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