High-accurate satellite navigation is the most important observation technique in geodesy und surveying. Providing observations and derived products for the satellite navigation systems GPS, GLONASS, Galileo, BeiDou, and QZSS is our main task.

In order to use satellite navigation in applications such as surveying or early warning systems for earthquakes or tsunamis, the solutions must not only be highly accurate, reliable, and continuous, but also be available with a delay of not more than a few seconds. To this end, we provide GNSS observations and products for different satellite constellations in real-time.

The high-accurate International Terrestrial Reference Frame (ITRF) is the metric basis for quantification with respect to Earth surface and essential for many theoretical and practical applications, such as the quantification of sea surface height and its change. Our research involves new methods and innovative techniques for the best possible multi-technique integration for the realization of consistent TRF, CRF (Celestial Reference Frame), and EOP (Earth Orientation Parameters).

The new working group set up in 2023 is working on three different research areas in the Astrogeodesy project: Radio astronomy, astrometry, and geodesy. The project aims to improve the accuracy and capability of the Very Long Baseline Interferometry (VLBI) technique used for geodesy to observe cosmological celestial objects like active galactic nuclei (AGNs). The new generation of geodetic VLBI system, named VLBI Global Observing System (VGOS), consists of a global array of radio telescopes with the ambitious goal of achieving, on global scales, high-accuracy measurements of station (antenna) positions and station velocities as well as Earth Orientation parameters.

The observations of geodetic GNSS ground stations can be used to measure the water vapor content above the stations. GNSS data from geodetic receivers are operationally analysed at GFZ and the products are used to improve regional and global weather forecasts and for climate studies. In the last two decades, ground-based GNSS technique for atmospheric sounding (GNSS meteorology) have developed rapidly and are now a standard method for atmospheric remote sensing.

GNSS radio occultation measurements from low Earth orbiting satellites can be used to derive globally distributed vertical profiles of atmospheric parameters, as, e.g., temperature, water vapor or electron density. This technique is currently operationally applied at GFZ using the data from GRACE, TerraSAR-X and TanDEM-X. The analysis results are provided for the provision of global weather forecasts and used for climate studies.

GNSS signals are reflected by water, ice and land surfaces. This feature is used to derive properties of the reflecting surface, as, e.g., altimetric height, roughness, soil moisture or snow properties. This new and innovative remote sensing technique is versatilely applied and improved at GFZ. For this purpose experiments with GNSS receivers on the Earth surface and aboard airships, aircrafts and satellites are planned and carried out.