Improvement of global ionospheric VTEC maps by using kriging interpolation technique

In this work, a geostatistic interpolation algorithm, called kriging, has been applied to improve the Technical University of Catalonia (UPC) global ionospheric maps (GIMs) computed with GPS data. This new UPC GIM, from now on UPC kriging GIM, has lower RMS in the observed slant total electron content (STEC) than the current UPC GIM and IGS GIM. Improvements are about 16% and 2%, respectively, using the data of several worldwide distributed GPS stations (self-consistency test). The UPC kriging GIM also presents a better performance than UPC GIM regarding the vertical total electron content (VTEC) measurements from TOPEX/Poseidon and JASON dual-frequency altimetric data. For both standard deviation and RMS, this improvement is about 0.3 TECU (6%) and 0.1 TECU (3%) for TOPEX and JASON, respectively. Moreover, it has also been shown a certain accuracy improvement of the resultant IGS GIM when the UPC kriging GIM replaces the present UPC GIM in the corresponding combination.