Improving the Accuracy of Regional Ionospheric Delay Correction with Modified Single-Layer Model

Elimination of Ionospheric delay is necessary to improve user positioning accuracy. Ionospheric delay can be reduced through correction message, and a method is used to provide correction for vertical delay so that any user can use it. The user calculates the slant delay correction for each satellite using the vertical delay correction and obliquity factor. This method is based on the ionospheric delay model assuming a single-layer thin shell. However, the single-layer ionospheric delay model has limitations in reproducing the actual slant delay, which causes errors in the process of generating and applying correction. In this study, a new model that added a correction term to the single-layer ionospheric delay model by considering the electron density distribution using the Chapman profile was proposed. Then, using the proposed model, a spherical harmonics modeling process of vertical delay was proposed to generate correction. IRI model-based simulation analysis was performed to analyze the accuracy of the generated correction. Five reference stations were set up in Europe and the accuracy was analyzed after generating correction. As a result of the analysis, the residual error was reduced by 30-70% compared to the conventional model that only considers vertical delay. Additionally, as a result of analyzing the residual error according to elevation angles, the residual error was reduced at all elevation angles. After analyzing the accuracy of the correction, the user inside the reference station network was set up and the user's positioning accuracy was analyzed. As a result, the positioning accuracy was improved by 60%, and the position error converged to within 10cm within about 6 minutes.