sentences:  From 1977-1982 he was a member of the Satellite Geodesy Commission of DGK and the Netherlands.From 1978-2000 he had full Professorship (Universitäts-Professor) at the University of Bonn and was Director of the Geodetic Institute.His work included research in statistics, deformation measurements, variance-covariance estimations in geodesy and immobiles, optimization of geodetic networks and datum transformations of geodetic systems, and satellite altimetry.