Performance of spatial interpolation methods in predicting GNSS zenith total delay

Abstract

This study proposes an alternative approach to the grid-wise VMF1 over Europe, through spatial interpolation of the site-wise VMF1 product. The performance of Ordinary Kriging and IDW was evaluated for predicting ZTD. Using 2020 data collected at 24 GNSS stations, two scenarios were constructed for February and August. Ordinary Kriging and IDW predictions were performed by making model adjustments via performance metrics and method successes were compared. The results showed that the ordinary kriging achieved a success rate of 83.2 %, while the IDW method achieved 77.1 % success. We compared the results with the grid-wise VMF1 to control the accuracy of spatial interpolations. Finally, the methods proposed as alternatives to gridded VMF1 were verified through the CSRS-PPP(ZTD). Ordinary-Kriging (RMSEFeb: [0.92–2.95 cm]; RMSEAug: [1.76–3.85 cm]) was in better compliance with the CSRS-PPP(ZTD), compared to the grid-wise VMF1 (RMSEFeb: [1.59–3.01 cm]; RMSEAug: [2.32–3.93 cm]). These results support that the quality of gridded products can be improved by spatial interpolations.