1. Ph.D. Candidate, Institute of Engineering Geodesy and Measurement Systems, Graz Univ. of Technology, Steyrergasse 30, 8010 Graz, Austria (corresponding author).
2. Full Professor and Head of Institute, Institute of Engineering Geodesy and Measurement Systems, Graz Univ. of Technology, Steyrergasse 30, 8010 Graz, Austria.