1. École Polytechnique Fédérale de Lausanne, Switzerland, *EPFL ENAC IIE TOPOGC C2 398 (Bâtiment GC), Station 18CH‐1015LausanneSwitzerland
2. School of Rural and Surveying EngineeringNational Technical University of AthensIroon Polytechniou 915780AthensGreece