A REVIEW OF GPS-BASED ZENITH PATH DELAY ESTIMATION AND ITS APPLICATION IN NIGERIA

Abstract

As the GPS signals traverse the tropospheric layers to the receivers on the ground, they are refracted and bend, thereby causing delay on their arrival time and in turns affecting positioning accuracy in the horizontal and vertical components. This delay which is one of the sources of positioning errors in GPS observation is known as Zenith Path Delay (ZPD). Estimation of ZPD during GPS data analysis is crucial for improving GPS positioning accuracy and assimilation into Numerical Weather Prediction (NWP) models for improved weather outlook and climate studies. This is remarkable, especially for tropical region noted for highly dynamic weather and climate system due to high moisture contents. However, the development of GPS infrastructure in Nigeria is relatively new. The NIGerian reference GNSS NETwork (NIGNET) is a network of GPS continuously operating reference stations (CORS) which was set up as a surveying infrastructure by the Federal Government of Nigeria through the Office of the Surveyor General of the Federation in about a decade ago. Nevertheless, there exist very limited numbers of literatures discussing GPS-based estimation of ZPD and its applications over Nigeria. Therefore, this paper presents a review of literature on ZPD estimation and its applications over Nigeria. A systematic review approach is adopted; literature materials were downloaded from web-based archives: Google Scholar, Scopus, ScienceDirect, Researchgate, Springer and other sources.