TEC derived from local GPS network in Pakistan and comparison with IRI-2016 and IRI-PLAS 2017

The existing global network of continuously operating stand-alone GNSS reference stations provides an opportunity to estimate total electron content (TEC) from raw Global Positioning System (GPS) measurements. The TEC driven from a local GPS network in Pakistan was compared to two international models: IRI-2016 and IRI-PLAS 2017. The performance was analyzed statistically based on residual analysis, RMSE and correlation. It is observed that the TEC estimated by all three methods follows the same diurnal trend where it maximizes around noon ( $$12:00 {-} 14:00 LT$$ ) and reduces in the afternoon ( $$15:00 {-} 17:00 LT$$ ). Both empirical models provide a better estimation of nighttime TEC as compared to daytime TEC and exhibit maximum deviation in the month of April with the lowest deviation in December. The IRI-2016 underestimates TEC by $$5 - 10 TECU,$$ whereas the IRI-PLAS 2017 overestimates TEC by $$10 - 22 TECU$$ . However, the IRI-2016 conforms better to GPS-TEC ( $$\overline{\gamma } = 0.9710$$ ) as compared to IRI-PLAS 2017 ( $$\overline{\gamma } = 0.8337$$ ). The study shows that local GNSS stations in collaboration with TEC estimated from global models may be used in development of an efficient local TEC model over Pakistan which will not only assist in local ionosphere studies but also aid in improving the positioning accuracy.