Non-parametric and semi-parametric regional modeling of the ionospheric vertical total electron content using ground-based GPS observations

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2013

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Durmaz, Murat

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Different global and regional models have been proposed for modeling of Vertical Total Electron Content(VTEC). Basis functions such as Spherical Harmonics and tensor products of univariate B-Splines are used for global and regional modeling respectively. The coefficients of the basis functions and Differential Code Biases (DCB) of satellites and receivers are treated as parameters and estimated from geometry-free linear combinations. In this work, a new approach based on non-parametric and semi-parametric methods is proposed to model spatio-temporal variations of VTEC. Multivariate Adaptive Regression Splines (MARS) and B-splines (BMARS) are adapted for regional VTEC modeling. Moreover, a semi-parametric modeling technique is developed where receiver DCBs can also be estimated. The parametric part of the semi-parametric model represents the receiver DCBs, whereas the non-parametric part is related to VTEC. The developed methods are implemented in an extensible software package. Both methods are applied to regional VTEC modeling over different regions and times. The results are compared both numerically and visually with another regional method and Global Ionosphere Maps (GIMs) provided by Center for Orbit Determination in Europe (CODE). The estimated receiver DCBs are also compared with the estimates of the other regional method and the ones that are published by CODE. Analysis of the results show that the developed technique can deliver similar VTEC maps and receiver DCB estimates with less number of terms. Additionally, the proposed method is validated by cross-validation and single-frequency point positioning indicating that the developed method is capable of delivering efficient and accurate regional VTEC models which provide better positioning estimates.

Subject Keywords

Ionospheric electron density., Global Positioning System., Ionospheric electron density.

URI

http://etd.lib.metu.edu.tr/upload/12616632/index.pdf
https://hdl.handle.net/11511/23181

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

M. Durmaz, “Non-parametric and semi-parametric regional modeling of the ionospheric vertical total electron content using ground-based GPS observations,” Ph.D. - Doctoral Program, Middle East Technical University, 2013.