IGS GIM을 활용한 지역적 Klobuchar 모델의 야간지연 상수와 보정계수 동시 추정

Abstract

In Global Navigation Satellite System (GNSS) signal transmission, the ionosphere is the most significant source of error. The Klobuchar model, a widely used ionospheric error correction model, relies on correction coefficients transmitted in Global Positioning System (GPS) navigation messages to provide global coverage. However, its accuracy is limited to approximately 50–60%. In this study, correction coefficients and Delay Constant (DC) values were estimated using International GNSS Service (IGS) Global Ionospheric Map (GIM) data to enhance the accuracy of the regional Klobuchar model, and the resulting improvements were analyzed. The grid point range for estimating the correction coefficients was defined as latitude 22.5–50° and longitude 105–150°, considering the Ionosphere Pierce Point (IPP) range over the Korean Peninsula. After calculating the Vertical Total Electron Content (VTEC) for each model, correction coefficients and DC values were simultaneously estimated using the least squares method. To evaluate the performance, the DC values were analyzed over periods with varying solar activity, and accuracy was validated based on VTEC Root Mean Square Error (RMSE) and positioning accuracy using IGS GIM as a reference. When DC values were estimated simultaneously, the VTEC RMSE improved by 54.8–74.4% compared to the original Klobuchar model, regardless of the solar activity intensity. Furthermore, positioning results at the Daejeon Station indicated horizontal accuracy improvements of approximately 1.7–40.0% and vertical accuracy improvements of approximately 34.8–37.4%.