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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Discussion papers
https://doi.org/10.5194/angeo-2018-121
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/angeo-2018-121
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Regular paper 12 Dec 2018

Regular paper | 12 Dec 2018

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Annales Geophysicae (ANGEO).

Regional Ionosphere Mapping Using Zero Difference GPS Carrier Phase

Heba Tawfeek1, Ahmed Sedeek2, Mostafa Rabah3, and Gamal El-Fiky1 Heba Tawfeek et al.
  • 1Faculty of Engineering, Zagazig University, Egypt
  • 2Higher Institute of Engineering and Technology, El-Behira, Egypt
  • 3Benha Faculty of Engineering, Benha University, Egypt

Abstract. Ionospheric delay, can be derived from dual frequency GNSS signals, and then converted into the Vertical Total Electron Contents (VTEC) along the signal path. Various models were devised to calculate VTEC. Examples of such models are the polynomial function model and spherical harmonics model. A common hypothesis of these models is that they are constructed based on the assumption that the entire electron content in the ionosphere is concentrated in a single thin shell at a selected height above Earth.

The primary goal of the current research to develop an algorithm capable of producing VTEC maps on an hourly basis, using carrier phase observations from dual frequency GPS receiver. The developed algorithm uses a single GPS station (Zero-difference) to map VTEC over a regional area.

The carrier phase measurements are much more precise than the code pseudorange measurements, but they contain an ambiguous term. If such ambiguities are fixed, thence the carrier phase measurements become as unambiguous pseudoranges, but accurate at the level of few millimeters.

In current research Sequential Least Square Adjustment (SLSA) was considered to fix ambiguity term in carrier phase observations. The proposed algorithm was written using MATLAB and Called (ZDPID). Two GPS stations (ANKR and BSHM) were used from IGS network to evaluate the developed code, VTEC values were estimated over these two stations. Results of the proposed algorithm were compared with the Global Ionosphere Maps (GIMs), which is generally used as a reference. The results show that the mean difference between VTEC from GIM and estimated VTEC at ANKR station is ranging from −2.1 to 3.67 TECU and its RMS is 0.44. The mean difference between VTEC from GIM and estimated VTEC at BSHM station is ranging from −0.29 to 3.65 TECU and its RMS is 0.38. Another three GPS stations in Egypt were used to generate regional ionosphere maps over Nile Delta, Egypt. The mean differences between VTEC from GIM and estimated VTEC at SAID station is ranging from −1.1 to 3.69 TECU and its RMS is 0.37, from −1.29 to 3.27 TECU for HELW station with RMS equal 0.39, and from 0.2 to 4.2 TECU for BORG station with RMS equal 0.46. Therefore, the proposed algorithm can be used to estimate VTEC efficiently.

Heba Tawfeek et al.
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