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The Second Order Refraction Effects for GPS Signals Propagation in Ionosphere

Alexander Prokopov, Alla Zanimonska
Kharkov State Research Institute of Metrology, Mironositskaya st. 42, 61002, Kharkov,
Ukraine

E-mail: nil1@metrology.kharkov.ua

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Dual frequency method of GPS measurements is based on the assumption that group (phase) delays of electromagnetic signals are defined with neglect of the second order refraction effects (particularly the influence of the Earth’s magnetic field, the contribution of the electron density quadratic terms in the series expansion of the refractive index, the lengthening and spatial separating effects of the ray paths with different carrier frequencies). However, some authors [1-3] showed that for large values of the electron density on low elevation angles this assumption leads to the residual range error, which amounts to several sm.

In this article, methods of modeling and elimination of the second order ionospheric errors, caused by effects referred above, are studied. Three approaches to solving this problem are discussed. That are instrumental approach (it’s typical of it to use the results of additional in comparison with 2-frequency method parameters measurements), methodical approach (when the independently defined refractive error correction is put in the results of the measurements) and combined one.

The physico-mathematical models are developed and the measurement equations are obtained in the framework of these approaches. In particular, 6-frequency and 3frequency methods of allowing for the second order refractive effects affecting on GPS measurements are suggested.

References:

[1] Min Gu, F. K. Brunner. An improved model for the dual frequency ionospheric correction of GPS observations// Manuscripta geodetica. – 1990. – Springer-Verlag. – pp.205 – 214.
[2] Çàí3ìîíñüêà À.ª., Ï<eth>îêîïîâ À.Â. Îö3íêà <eth>åô<eth>àêö3éíèõ åôåêò3â ä<eth>óãîãîïî<eth>ÿäêó â ìîäåëÿõ 3îíîñôå<eth>è äëÿ GPS çàñòîñóâàíü. //Ãåîäåç3ÿ, êà<eth>òîã<eth>àô3ÿ 3 àå<eth>îôîòîçí3ìàííÿ. - 161. - 2001.- ñ. 24-29.
[3] Bassiri S., Hajj G.A. Modeling the Global Positioning System SignalPropagation Through the Ionosphere// TDA Progress Report 42-110. – August 15, 1992. – pp. 92 – 103.