Tropospheric Zenith Delay Prediction Accuracy for High-Precision GPS Positioning and Navigation

Abstract

In this paper, we determine mean bias and root-mean-square RMS scatter for a large number of zenith tropospheric propagation delay prediction models developed in the last few decades by comparing the models against ray-tracing results using a 1-year data set of radiosonde profiles. We conclude that the hydrostatic zenith delay can be predicted with submillimeter accuracy, provided that accurate measurements of station pressure are available. For wet zenith delay, the models differ significantly in accuracy, but show very similar RMS scatter. Our analyses show that the wet zenith delay can typically be predicted with a precision of approximately 3 cm using meteorological data. The prediction of the total delay by models typically used in airborne navigation indicates a much poorer accuracy, leading to prediction biases ranging from around 6 cm to more than 20 cm. In general, all the models tested perform significantly better at midlatitudes than at low latitudes. for precise airborne relative positioning is further complicated by the large height difference generally

Tropospheric delay in microwave propagation for tropical atmosphere based on data from the Indian subcontinent

“…Considering all the eight stations together the mean of the absolute difference for SAAS and Unified model are 1.57 and 0.96 cm, respectively. In the case of wet delay, the Unified models developed in the present analysis are much better than the existing models (Ifadis, 1986;Mendes and Langley, 1998). The mean absolute difference of the unified model based on e S varies from about 4 to 5 cm, whereas in case of other two global models it varies from about 5 to 11 cm.…”

“…It would be worth in this context to compare the above relation with those reported by other investigators. Mendes and Langley (1998) …”

“…Even though reasonably accurate models are available for ZHD (Saastamoinen, 1972;Elgered et al, 1991) based on the ambient surface pressure (P S Þ, which can be applied globally, the empirical models proposed for the ZWD (Mendes and Langley, 1998;Davis et al, 1985;Ifadis, 1986) based on surface humidity, are mostly region specific, because of the large spatial heterogeneity and temporal variability of atmospheric water vapor. In other words, while the model parameters evolved for ZHD is fairly constant at different locations over the globe, those parameters evolved for ZWD show significant variations from one location to the other.…”

A regional tropospheric model for airborne GPS applications

“…However, these models and methods are only suitable for a kinematic station on the ground (Xu, 2000(Xu, , 2007. If the kinematic station is several kilometers higher than the ground reference stations, the precisions of tropospheric delays from these models will be decreased rapidly (Collins and Langley, 1997;Mendes and Langley, 1998). Therefore, it is necessary to creating a more suitable troposphere model for high altitude kinematic stations, such as airplane, airship and INSAR.…”

Assessment of time-series of troposphere zenith delays derived from the Global Data Assimilation System numerical weather model

“…Some models are explicitly dependent on the surface meteorological data, while others are site dependent (the latitude and the height are required) and/or day-of-year dependent. Mendes and Langley (1998) assessed a number of zenith delay models using a one-year data set of radiosonde profiles from 50 stations distributed worldwide. They concluded that the Saastamoinen model (Saastamoinen 1973) is the most accurate with sub-millimeter bias and RMS scatter for the hydrostatic zenith delay with respect to the benchmark values.…”