The International Association of Geodesy (IAG) recommends the International Terrestrial Reference Frame (ITRF) as the standard terrestrial reference frame for positioning, satellite navigation and Earth science applications, as well as for the definition and alignment of national and regional reference frames (see IAG Resolution No. 1, 2019). The importance of geodetic reference frames has been recognized by the United Nations, too. In February 2015, the UN General Assembly adopted its first geospatial resolution “A Global Geodetic Reference Frame for Sustainable Development”.
The ITRF provides the fundamental basis to refer the geodetic observations and estimated parameters to a unified global basis. High accuracy, consistency and long-term stability are required for precisely monitoring global change phenomena as well as for precise positioning applications on and near the Earth’s surface. The ITRF comprises concrete points (markers) attached to the solid Earth crust with precisely determined coordinates (mean 3D positions of the stations and their motions).