A theoretical and experimental comparison of the ionosphere‐free L1 pseudorange and the ionosphere‐free linear combination pseudorange by dual‐frequency SBAS users

This study verifies the performance of the ionosphere-free L1 pseudorange for dual-frequency space-based augmentation systems (SBAS) users by both of theoretical analysis and experiments with actual GPS data. Although the dual-frequency pseudorange from ionosphere-free linear combinations is commonly used as a standard method, the ionosphere-free L1 range based on the weighted Hatch filter has advantages in terms of the amplification factor caused by a dual-frequency combination and filter weights optimised by the least-squares method. For the experimental analysis, RINEX data were collected from five National Geographic Information Institute reference stations on the Korean peninsula and used to generate an SBAS correction message following international SBAS specifications. The experimental results show that using the proposed method results in a 29% improvement in the range domain compared with the use of a traditional ionosphere-free linear combination filter. In the position domain, the proposed method shows a horizontal accuracy improvement of 16% after the application of post-processed SBAS orbit/clock corrections w.r.t. the traditional filter. Finally, this study also demonstrates that the accuracy of dual-frequency users can surpass than that of single-frequency SBAS users only if corrections are estimated with ionospheric delay-free measurements in the master station as well.