1. Graduate Student, School of Rural and Surveying Engineering, National Technical Univ. of Athens, 5, Iroon Polytechniou St., Athens 15770, Greece.
2. Ph.D. Candidate, School of Rural and Surveying Engineering, National Technical Univ. of Athens, 5, Iroon Polytechniou St., Athens 15770, Greece.
3. Assistant Professor, School of Rural and Surveying Engineering, National Technical Univ. of Athens, 5, Iroon Polytechniou St., Athens 15770, Greece (corresponding author).