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The TropGrid2 standard tropospheric correction model

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Abstract

TropGrid2 is a new version of a tropospheric model that is based on climatology and provides tropospheric propagation delay corrections for standard positioning users without temperature, pressure and humidity measurements. Zenith hydrostatic and wet delays are modeled as special harmonic functions taking seasonal and diurnal variations into consideration. The grid-point values are height-reduced and can be interpolated horizontally to the user position. The database used to derive this model consists of more than 9 years of 3D numerical weather fields of the NOAA NCEP GDAS weather model. We validated this standard model using 10 years of GPS-derived zenith path delays at 290 International GPS service reference stations. The gridded version is accurate at a level of 3.8 cm (root mean square in zenith direction) on global average; the average long-term bias is −0.3 cm. The standard deviations computed by the model turn out to be slightly too pessimistic for almost all stations under investigation, in contrast to the site-specific version, which is only marginally (1 mm) more accurate on global scale.

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Abbreviations

CDDIS:

Crustal Dynamics Data Information System

ECMWF:

European Centre for Medium-Range Weather Forecasts

ERA15:

ECMWF re-analysis (fields 1978–1994)

ESA:

European Space Agency

GAL:

TROPO ESA-developed Galileo tropospheric correction model

GDAS:

Global data assimilation system

GTN:

Global tropospheric correction model for navigation

IGS:

International GPS Service

IWV:

Integrated water vapor

MOPS:

Minimum Operational Performance Standards

NCEP:

National Center for Environmental Prediction

NOAA:

National Oceanic and Atmospheric Administration

NWM:

Numerical weather model

PW:

Precipitable water

RINEX:

Receiver-Independent Exchange Format

RMS:

Root mean square

RTCA:

RTCA, Inc

ZHD:

Zenith hydrostatic delay

ZPD:

Zenith path delay (synonym of: Zenith total delay)

ZWD:

Zenith wet delay

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Acknowledgments

The author would like to express his gratitude toward NOAA/NCEP for making the GDAS real-time weather fields from June 1999 to September 2008 available. The supply of reference zenith path delays processed from GPS data by the IGS is highly appreciated. Parts of this work were conducted in the COSMEMOS project that is partially funded by the European Union Framework Programme (FP7/2007-2013) under grant agreement no. 287162. All result tables used in this analysis are available from the author upon request.

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Correspondence to Torben Schüler.

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Schüler, T. The TropGrid2 standard tropospheric correction model. GPS Solut 18, 123–131 (2014). https://doi.org/10.1007/s10291-013-0316-x

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