Comparative Analysis of Five Standard Dry Tropospheric Delay Models for Estimation of Dry Tropospheric Delay in GNSS Positioning.

Abstract

The atmosphere causing the delay in GPS signals consists of two main layers, ionosphere and troposphere. The ionospheric bias can be mitigated using dual frequency receivers. Unlike the ionospheric bias, the tropospheric bias cannot be removed using the same procedure. Compensation for the tropospheric bias is often carried out using a standard tropospheric model. In order to investigate the impact of different dry tropospheric models on GPS accuracy, simultaneous hourly observations was carried out at some selected stations in Minna. The tropospheric errors obtained using five standard tropospheric models namely, the Saastamoinen model (which was adopted as the standard model), Hopfield model, Davis et al. model, Saastamoinen model (Using Ground Meteorological Data) and Altshuler and Kalaghan model were compared. It was deduced from the results that at all the stations, the Saastamoinen Model (Using Ground Meteorological Data), has 100% correlation with the adopted standard Dry Tropospheric Model (Saastamoinen model). While a standard error of 0.285mm, 1.446mm and 2.899mm were respectively obtained for Davis et al. Model, Hopefield model and Altshuler and Kalaghan (A&K) Model. However, the statistical test performed on the overall results indicated that there is no significant difference in the performance of the five tropospheric models at 0.05 significance level. It was therefore, concluded that either of the five models evaluated in this study can perform well in the study area, nevertheless, the choice of Saastamoinen Model, Saastamoinen Model (Ground Meteorological Data) and Davis et al. Model will be more preferable.