Atmospheric GPS slant path delays and ray tracing through numerical weather models, a comparison

Abstract

We compare tropospheric single path delays measured by the Global Positioning System (GPS) and calculated by a numerical weather prediction (NWP) model. We discuss the use of GPS slant path delays for NWP and the use of NWP models for better GPS data processing.We use the Bernese Software 4.2 to determine undifferenced slant path delays caused by the neutral atmosphere from undifferenced ground based GPS observations. We calculate the same delays using the global NWP model from the European Centre for Medium-Range Weather Forecasts (ECMWF) with ray tracing. The comparison indicates that the level of agreement (1 – 1.5 cm for the zenith total delay) depends on the amount of water vapor present in the atmosphere.