Abstract
Abstract. In order to further study the variation characteristics of the nighttime ionospheric accuracy of the Klobuchar model and the correlation between the nighttime ionospheric accuracy of the Klobuchar model and solar activity intensity. In this paper, a method for comparative analysis on solar activity intensity in the high, medium and low solar activity years has been proposed. The GIM provided by the IGS Center from 2008 to 2018 are treated as reference values to analyze the nighttime accuracy of the Klobuchar model for annual, seasonal, and monthly changes in high solar activity, medium solar activity and low solar activity. The results are: (1) The nighttime accuracy of the Klobuchar model is best in the medium solar activity, followed in the low solar activity and the worst in the high solar activity. (2) The Bias and RMS of the Klobuchar model at nighttime had obviously semi-annual and seasonal variations in high and medium solar activity. (3) The nighttime accuracy of the Klobuchar model did not vary with Bias and RMS changes at nighttime.
Highlights
Ionospheric delay is one of the mainly error sources in Global Navigation Satellite System (GNSS)
All of the above methods can improve the nighttime accuracy of the Klobuchar model, but few documents analyze the nighttime accuracy of the model from these aspects, such as ionospheric electron content varies at rates of season, semiyear, year, and solar activity cycle on time series
In terms of the fluctuation range of the nighttime average accuracy of the Klobuchar model, the fluctuation of the nighttime average annual accuracy is greater than the fluctuation range of the medium solar activity and the high solar activity
Summary
Ionospheric delay is one of the mainly error sources in Global Navigation Satellite System (GNSS). For single-frequency GNSS users, the Klobuchar model is the most effective way to correct for the ionospheric delay. In order to meet the requirements of single-frequency users for the accuracy of navigation and position, many researchers are committed to the correction of the nighttime ionospheric VTEC. WANG et al [5] considering the nighttime ionospheric delay with the variation of the latitude quadratic parabola, a 10-parameter model is established. The characteristics of daily variation and seasonal variation with the ionospheric VTEC of Curtin University in 2013 and 2014 were analyzed by using the dual-frequency BeiDou GEO data, an 16-parameters regional model was established by dividing the time into three sections and regarded it as a linear change [9]. In this paper, the high-precision GIM data from 2008-2018 provided by the IGS Center was used as a reference value to study the accuracy variation of the Klobuchar model in the nighttime during the 24th solar activity cycle and the influencing factors, and provide a reference for the improvement and regionalization of the Klobuchar model
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