Results of Experimental Assessment of Single-Frequency User Positioning Accuracy Using a GLONASS Ionospheric Model Refined by Dual-Frequency Measurements for a Regional Network of User Receivers

Yu. V. Chubarov

Transactions of IAA RAS, issue 76, 25–31 (2026)

DOI: 10.32876/ApplAstron.76.25-31

Keywords: GLONASS ionosphere model, local ionosphere model, total electron content (TEC), dual-frequency navigation measurements, ionospheric signal delay, positioning accuracy, single-frequency positioning

Abstract

The purpose of this paper is to experimentally validate two stages of the methodology for determining ionospheric data for the operational positioning mode of GLONASS users. These stages include the estimation of differential code delays and the refinement of the local ionospheric model parameters. The study focuses on improving the positioning accuracy of single-frequency user equipment by utilizing refined local ionospheric model parameters. Additionally, a comparative assessment of the obtained solutions is conducted against those based on the GLONASS ionospheric model recommended in the GLONASS Interface Control Document (GLONASS ICD) for open-access code-division signals, as well as the GPS Klobuchar ionospheric model specified in the official GPS system documentation. To develop the refined local ionospheric model, the ionospheric model presented in the GLONASS ICD was selected as the baseline model. The input data comprised dual-frequency code and carrier-phase measurements from a regional network of user receivers, digital navigation message data, and daily mean solar and geomagnetic activity indices. The model parameters were refined by comparing the ionospheric delay calculated using the baseline GLONASS model with reference ionospheric delay values. These reference values were determined through linear combinations of dualfrequency measurements from a reference receiver. The experimental evaluation of positioning accuracy was carried out using the root-mean-square error of coordinate residuals derived from single-frequency L1 measurements relative to the regional network station coordinates of the user receivers. In summary, the algorithms for estimating differential code delays and refining the local GLONASS ionospheric model`s parameters were validated. Results show that employing the refined local GLONASS ionospheric model reduces the root-mean-square error of coordinate residuals for single-frequency user equipment by up to 17 % compared to using the baseline GLONASS model. Furthermore, a comparative analysis between navigation errors of single-frequency GPS users — using the GPS Klobuchar model versus the refined GLONASS model — confirmed an accuracy advantage of up to 15 % for the refined GLONASS model. It is concluded that the developed algorithms are practically applicable in implementing the methodology for determining ionospheric data for the operational positioning mode of GLONASS users.

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