Preliminary study on the variation of zenith tropospheric delay with altitude

Abstract

Tropospheric delay is a major source of error for ground-to-air, air-to-ground observation and various types of radio navigation positioning technology, and it is usually corrected by tropospheric delay models for the majority of real-time navigation users. Traditional tropospheric delay models (such as Hopfield, Saastamonion, UNB3, etc.) take the cumulative delay of the whole atmosphere into account, and surface meteorological data is needed as the input to some of them. It's hard to meet the requirement of the atmospheric delay correction for the real-time user at arbitrary time and height by using the old models. We consequently adopt the method modeling the zenith tropospheric delay (ZTD) with the altitude directly to solve this problem. In this paper, the ZTDs at different altitude were calculated by the ERA-Interim reanalysis data in 2004 at 1.5 grid points, and the spatiotemporal characteristics of ZTD varying with altitude was studied detailedly. A fitting analysis between ZTD and altitude was carried out by a piecewise function afterwards. The accuracy of the fitting function above was assessed carefully, and we also tested it by the ZTDs come from 45 IGS (International GNSS Service) stations distributed all over the world from 2008 to 2010. The results are as following: The deviation of the fitting and the integral ZTDs come from ERA-Interim is less than 1 cm at all the grid point, and which is stable in the range of 45 km high. The fitting and IGS ZTDs comparisons at 45 stations show a mean yearly difference of no more than 1 cm with a mean SD of about 4.3 cm. The piecewise fitting function we constructed could be applied as a preliminary model of the ZTD varying with altitude, and has important application value in real-time navigation and positioning. © 2013 Springer-Verlag Berlin Heidelberg.