sentences:  From the 1930s he concentrated on the study of the reference ellipsoid and phase diagrams, as well as the elliptical shape of the Equator, the level spheroid, and the triaxial Jacobi ellipsoid.Hopfner did pioneering work on the determination of geographical distances without the use 
  of wires (the first employment of time-signals), as well as on gravimetry.His study of the Earth's magnetic field helped make a name for the ZAMG, or Central Institute for Meteorology and Geodynamics ("Zentralanstalt für Meteorologie und Geodynamik") in Vienna.