Assessing the Performance of Models for Ionospheric Correction for Single-frequency GNSS Positioning

Currently, the majority of users of global navigation satellite systems (GNSS) still apply single frequency equipment to estimate their coordinates. Since the ionosphere introduces a significant delay to the GNSS signals, single-frequency satellite measurements require a regular correction to remove an error occurring due to ionospheric propagation. Nowadays, there are number of ionospheric models produced to correct navigation measurements. The performance accuracy of the models may vary significantly depending on season, local time, latitude and geophysical conditions. In the study we analyze the performance accuracy of four models: Klobuchar (GPS) model, GLONASS model, Beidou (BDGIM) model as well as the GEMTEC model. The precision of the models is evaluated in the term of total electron content (TEC) values they provide. In the study we also estimate the model accuracy based on the final single-frequency positioning solution. We used the data from 3 GNSS stations at different latitudinal regions. To obtain relevant statistics we treat the set of the data for a long period of time. We calculate coordinates as a typical iterative single-frequency solution based on non-smoothed C/A pseudo ranges. We show that deteriorations of a solution with applying a correction occur more frequently in the near-polar regions, while less frequently in the equatorial regions. For example, the Klobuchar model increases the positioning error in the horizontal plane for more than 40% of cases at mid- and high-latitudes, while only ~ 20% at low latitudes. The best correction performance is revealed for BDGIM and GEMTEC models.