GNSS Meteorology on Moving Platforms

Advances and Limitations in Kinematic Water Vapor Estimation

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“Working Papers” explore the technical and scientific themes that underpin GNSS programs and applications. This regular column is coordinated by Prof. Dr.-Ing. Günter Hein.

Over the years, researchers have advanced the use of GPS receivers to measure water vapor content in the troposphere and model its effects on signal propagation. However, these techniques typically employ stationary GPS receivers. This column describes a method for measuring water vapor by GPS receivers on moving platforms and determining the associated atmospheric effects.

Torben Schüler

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Although GNSS is primarily designed for positioning, navigation, and timing applications, it can also be used to determine a quantity that is of major interest for meteorologists and climate researchers, namely, integrated water vapor. This gas plays a critical role for the energy balance of our atmosphere and is actually responsible for approximately 62 percent of the natural greenhouse effect. Consequently, the distribution of water vapor, as well as its spatial and temporal behavior, is important for climate predictions and weather forecasts.

Whilst GNSS-based integrated water vapor monitoring has become a well-established technique in static networks of reference stations, only very few efforts have yet been carried out to employ this method on moving platforms such as ships and aircraft. In this article, we will address kinematic water vapor estimation with GPS in kinematic mode. The results presented in this article feature the successful retrieval of vapor on the open sea via very long baselines for the first time. We will also outline the limitations inherent in the current use of GPS alone and the outlook for future benefits from a combination of GPS and Europe’s new Galileo system.

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Author Profiles

Torben Schüler received his diploma in geodesy and cartography from the University of Hannover in 1998. Afterwards, he joined the Institute of Geodesy and Navigation (University FAF Munich) as a research associate, earned a doctorate, and is now head of the GNSS/INS Laboratory at the same institute. His major research work is focused on precise GNSS positioning, including atmospheric and, in particular, tropospheric delay modeling. Schüler was heavily involved in the development of the standard tropospheric correction model for the Galileo satellite navigation system now being deployed.