1. Professor, DIIAR-Surveying, Geodesy and Geomatics Section, Politecnico di Milano, 20133 Milan, Italy.
2. Research Fellow, DIIAR-Surveying, Geodesy and Geomatics Section, Politecnico di Milano, 20133 Milan, Italy (corresponding author).
3. Research Fellow, DIIAR-Surveying, Geodesy and Geomatics Section, Politecnico di Milano, 20133 Milan, Italy.