VMF3/GPT3: refined discrete and empirical troposphere mapping functions

Abstract

Incorrect modeling of troposphere delays is one of the major error sources for space geodetic techniques such as Global Navigation Satellite Systems (GNSS) or Very Long Baseline Interferometry (VLBI). Over the years, many approaches have been devised which aim at mapping the delay of radio waves from zenith direction down to the observed elevation angle, so-called mapping functions. This paper contains a new approach intended to refine the currently most important discrete mapping function, the Vienna Mapping Functions 1 (VMF1), which is successively referred to as Vienna Mapping Functions 3 (VMF3). It is designed in such a way as to eliminate shortcomings in the empirical coefficients b and c and in the tuning for the specific elevation angle of 3 • . Ray-traced delays of the ray-tracer RADIATE serve as the basis for the calculation of new mapping function coefficients. Comparisons of modeled slant delays demonstrate the ability of VMF3 to approximate the underlying ray-traced delays more accurately than VMF1 does, in particular at low elevation angles. In other words, when requiring highest precision, VMF3 is to be preferable to VMF1. Aside from revising the discrete form of mapping functions, we also present a new empirical model named Global Pressure and Temperature 3 (GPT3) on a 5 • × 5 • as well as a 1 • × 1 • global grid, which is generally based on the same data. Its main components are hydrostatic and wet empirical mapping function coefficients derived from special averaging techniques of the respective (discrete) VMF3 data. In addition, GPT3 also contains a set of meteorological quantities which are adoptedas they stand from their prede-B Daniel Landskron

Impact of different NWM-derived mapping functions on VLBI and GPS analysis

“…It should be added that in the recent months, the ray tracer employed by VMF1 has been improved and a new set of mapping functions has been developed, called the VMF3 (Landskron and Böhm 2017). Therefore, future work will necessarily involve these new developments.…”

A Global Model for Estimating Tropospheric Delay and Weighted Mean Temperature Developed with Atmospheric Reanalysis Data from 1979 to 2017

“…The existing empirical models are roughly divided into two types. The first type models meteorological parameters and uses traditional tropospheric delay models, e.g., the Saastamoinen model or similar models, to calculate tropospheric delay [8][9][10][11][12][13][14][15]. The second type models tropospheric delay directly, which provides empirical tropospheric delay free of meteorological parameters [16][17][18].…”

An ERA5‐Based Model for Estimating Tropospheric Delay and Weighted Mean Temperature Over China With Improved Spatiotemporal Resolutions

“…Hitherto, scientists have built many empirical models, which are roughly divided into two types. The first type is based on the meteorological parameters, such as the UNB models (Collins & Langley, , ), the EGNOS model (Dodson et al, ; Penna et al, ), the TropGrid models (Krueger et al, ; Schüler, ), the GPT models (Böhm et al, , ; Lagler et al, ; Landskron & Böhm, ), and the ITG model (Yao et al, ). This type of models usually employs a table to represent empirical meteorological parameters and uses the Saastamoinen model or similar models to calculate tropospheric delays.…”

“…Recently, Landskron and Böhm (2018) built the GPT3 model. Compared with its predecessor GPT2w, this model only updated the empirical mapping function coefficients.…”

“…This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. the EGNOS model (Dodson et al, 1999;Penna et al, 2001), the TropGrid models (Krueger et al, 2005;Schüler, 2014), the GPT models (Böhm et al, 2007(Böhm et al, , 2015Lagler et al, 2013;Landskron & Böhm, 2018), and the ITG model (Yao et al, 2015). This type of models usually employs a table to represent empirical meteorological parameters and uses the Saastamoinen model or similar models to calculate tropospheric delays.…”