Improving GPS surveying with modeled ionospheric corrections

We model the ionospheric delay of Global Positioning System (GPS) signals w ith high precision and use it to correct single frequency (L1) GPS baseline estimations. We find that baselines up to 30 km in length are more precise ly determined using corrected L1 data than using dual frequency data. The h igh resolution ionospheric modeling technique (called HiRIM in this paper) is demonstrated with 195 days of data from a 25-site GPS network at similar to1 km spacing in central Japan. The network was designed for high vertica l precision tectonic studies. We compute ionospheric corrections using data from a surrounding grid of nine GPS sites spaced similar to 50 km. Based o n the observations from the surrounding grid, epoch and satellite specific ionospheric delays are interpolated to correct L1 observations from the int ernal sites. HiRIM has potential postprocessing and real-time applications in navigation, surveying, and GPS meteorology.