Berhard Hofmann-Wellenhof, born in 1951, is Professor for Navigation and Satellite Geodesy at the TU-Graz. He is Co-Author of numerous books and papers, among them"Global Positioning System", 5th ed., SpringerWienNewYork. Herbert Lichtenegger, born in 1941, is assistant professor at thenbsp;Institutenbsp;fornbsp;Navigation and Satellite Geodesy at the TU-Graz. He is Co-Author of numerous books and papers, among them"Global Positioning System", 5th ed., SpringerWienNewYork. Elmar Wasle, born in 1975, worksnbsp;for a private enterprise and is specialised in GPS.