The precise measurement of the earth has not yet been completed. However, it is of central importance, especially with regard to climate change and natural disasters: The precise description of the Earth's surface is crucial, for example, when it comes to the rise in sea level caused by the melting of the polar ice caps - one of the most imprecisely determined variables at present.
The overall goal of this research unit is the determination of highly accurate and long-term stable geodetic reference frames. Global reference frames are the metrological basis for earth system monitoring and other applications, such as the quantification of change processes in the Earth’s system, for example, by geodynamics and climate change, positioning and navigation on Earth and in space. This topic is of high societal relevance; therefore, the United Nations adopted the UN resolution “Global Geodetic Reference Frame for Sustainable Development” (GGRF, www.unggrf.org) on February 26, 2015.
Global geodetic reference frames are determined by a combination of measurements of the four main space-geodetic techniques all based on time measurements. The combination is usually done utilizing local surveys at globally distributed stations observing different techniques. However, the local measurement refers only to the geometry of the measuring systems, but not to their true reference points, so that systematic errors are unavoidable. Within the research unit, “time coherence” between the space-geodetic techniques will be introduced as a novel tie, called clock tie.
Closure measurements utilizing a common clock and common reference point for the space geodetic techniques will be performed first at the Geodetic Observatory Wettzell, Germany. It is planned that Wettzell will be connected to the Satellite Laser Ranging Station in Potsdam by means of a satellite link (ACES mission / Atomic Clock Ensemble in Space) via time transfer. The satellite laser ranging station at the German Research Centre for Geosciences in Potsdam will in turn be connected via fiber lines to the highly precise and stable time system of the Physikalisch-Technische Bundesanstalt PTB, the German National Metrological Institute. It will allow a quasi-error-free combination of the space-geodetic techniques and a significantly improved geodetic reference frame, the basis for the accurate observation of our planet Earth.
Members of the research group are: Deutsches GeoForschungsZentrum Potsdam, Physikalisch-Technische Bundesanstalt Braunschweig, Technische Universität Berlin, Universität Bremen, Universität Hannover and Universität der Bundeswehr München. The DFG is funding ten projects with four million euros for the first four years. The term is four years with the option to extend for a further four years.
Speaker of DFG Research Unit
Prof. Dr.-Ing. Ulrich Schreiber
Astronomical and Physical Geodesy, Department Aerospace and Geodesy, TUM School of Engineering and Design