Regional and optimal estimation of total electron content using pseudorange observations

Document Type : Research Article

Authors

1 Department of Surveying and Geomatics Engineering, Faculty of Engineering, University of Tehran

2 Faculty of engineering school of surveying engineering, University of Tehran

Abstract

Total Electron Content (TEC) is one of the most important factors in monitoring the variable structure of ionosphere. Global Positioning System (GPS) is a useful and affordable instrument in TEC prediction through ground receivers. In this research, Vertical Total Electron Content (VTEC) is calculated in a GPS station using code observations and an approach is introduced for precise, and local modeling of this quantity. For doing this, a geometry-free combination of P1 and P2 observables is made and TEC for every satellite in an epoch is obtained using this combination and Differential Code Biases (DCB) of satellite and receiver. The calculated parameter shows total electron content in the direction of signal propagation in ionosphere layer. Besides, a mapping function is used for transforming TEC to VTEC. For doing this transformation, there are various mapping functions the common examples of which are geometric mapping function and empirical mapping function. In order to increase the precision and reduce systematic errors of calculations, the geometric mapping function  is used. After calculation of VTEC for every satellite, it is necessary to obtain the amount of VTEC in zenith direction of the station. For doing this, a weighted function is used that inversely relates to the  elevation angle of the satellite. The proposed weighted function provides an optimum and precise formula for calculation of VTEC in zenith direction of the station. In order to investigate the accuracy of calculations, all of the results are compared with the VTEC grids of International GNSS Service (IGS), and finally, the conclusions for every specific method are shown like weighted average, normal average and nearest vertex. In other words, IGS ionospheric products are considered as accurate and precise VTEC and the results are compared with these VTECs. As everybody knows, IGS VTECs are produced in a grid and thus, for calculation of VTEC in a specific point, mathematical approaches like weighted average of VTECs in surrounded vertexes of the point should be used. Conclusions illustrate the calculation of VTEC using proposed approach has a good adaption with the  weighted average of VTECs around the Ankara grid station. The other results are also illustrated in diagrams. In addition, the periodic behavior of ionosphere at different times are also modeled, and the method is improved for optimum estimation of VTEC at various times. The only thing that is important is the local nature of this method, which is useful in one cell of IGS ionospheric network only.

Keywords

References

Amerian, Y., Hossainali, M., Voosoghi, B., Ghaffari, M. R., 2010, Tomographic Reconstruction of the Ionospheric Electron Density in term of wavelets: International Journal of Aerospace Science and Technology.
Arikan, F., Erol, C. B., and Arikan, O., 2004, Regularized estimation of vertical total electron content from GPS data for a desired time period: Radio Science, 39, RS6012, doi: 10.1029/2004 RS003061.
Arora, B. S., Morgan, J., Ord, S. M., Tingay, S. J., Hurley-Walker, N., Bell, M., Bernardi, G., Bhat, R., Briggs, F., Callingham, J. R., Deshpande, A. A., Dwarakanath, K. S., Ewall-Wice, A., Feng, L., For, B. Q., Hancock, P., Hazelton, B. J., Hindson, L., Jacobs, D., Johnston-Hollitt, M., Kapińska, A. D., Kudryavtseva, N., Lenc, E., McKinley, B., Mitchell, D., Oberoi, D., Offringa, A. R., Pindor, B., Procopio, P., Riding, J., Staveley-Smith, L., Wayth, R. B., Wu, C., Zheng, Q., Bowman, J. D., Cappallo, R. J., Corey, B. E., Emrich, D., Goeke, R., Greenhill, L. J., Kaplan, D. L., Kasper, J. C., Kratzenberg, E., Lonsdale, C. J., Lynch, M. J., McWhirter, S. R., Morales, M. F., Morgan, E., Prabu, T., Rogers, A. E. E., Roshi, A., Udaya Shankar, N., Srivani, K. S., Subrahmanyan, R., Waterson, M., Webster, R. L., Whitney, A. R., Williams, A., and Williams, C. L., 2015, Ionospheric Modelling using GPS to calibrate the MWA. 1: comparison of first order ionospheric effects between GPS models and MWA observations: Astronomical Society of Australia, Cambridge University Press, doi: 10.1017/pas.2015.
Gao, Y., and Liao, Z., 2002, Ionosphere Modeling Using Carrier Smoothed Ionosphere Observations from a Regional GPS Network: Geomatica, 56(2), 97-106
Deviren, M.N., and Arikan, F., 2013, spatio-temporal interpolation of total electron content using a GPS network.
Jakowski, N., Sardon, E., Engler, E., Jungstand, A., and Klahn, D., 1996, Relationships between GPS-signal propagation errors and EISCAT observations.
Leick, A., 2004, GPS Satellite Surveying, 3rd Edition: John Wiley and sons Inc., New Jersey.
Liao, X., 2000, Carrier Phase Based Ionosphere Recovery Over a Regional Area GPS Network: M. Sc. Thesis, University of Calgary.
Mylnikova, A. A., Yasyukevich, Y. V., Kunitsyn, V. E., Padokhin, A. M., 2014, Variability of GPS/GLONASS Differential Code Biases.
Nayir, H., Arikan, F., Arikan, O., and Erol, C. B., 2007, Total Electron Content Estimation with Reg-Est.
Otsuka, Y., Ogawa, T., Saito, A., Tsugawa, T., Fukao, S., and Miyazaki, S., 2002, A new technique for mapping of total electron content using GPS network in Japan: Earth Planets Space, 54, 63-70.
Seeber, G., 1993, Satellite Geodesy: Foundations, Methods and Application: Walter de Gruyter, Berlin and New York, 531.
Sharifi, M. A., and Farzaneh, S., 2017a, The ionosphere electron density spatio-temporal modeling based on the Slepian basis functions: Acta Geodaetica et Geophysica, 52(1), 5-18.
Sharifi, M. A., and Farzaneh, S., 2017b, The local ionospheric modeling by integration ground GPS observations and satellite altimetry data: Annals of Geophysics, 59(6), 0654.
Farzaneh, S., and Forootan, E., 2017c, Reconstructing Regional Ionospheric Electron Density: A Combined Spherical Slepian Function and Empirical Orthogonal Function Approach: Surveys in Geophysics, 1-21.
Sharifi, M. A., and Farzaneh, S., 2016, Local Ionospheric Modeling Using the Localized Global Ionospheric Map and Terrestrial GPS: Acta Geophysica, 64(1), 237-252.
Warnant, R., 1997, Reliability of the TEC computed using GPS measurements-The problem of hardware biases: Acta Geodaetica Geophysica et Montanistica Hungarica, 32(3-4), 451-459.
Iranian Journal of Geophysics
Volume 11, Issue 4
March 2018
Pages 54-66

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