1. Institute of Geomatics, Parc Mediterrani de la Tecnologia, Avinguda del Canal Olímpic s/n, E-08860 Castelldefels, Barcelona, Spain. E-mail: erlinda.biescas@ideg.es
2. Institute of Geomatics, Parc Mediterrani de la Tecnologia, Avinguda del Canal Olímpic s/n, E-08860 Castelldefels, Barcelona, Spain. E-mail: michele.crosetto@ideg.es
3. Institute of Geomatics, Parc Mediterrani de la Tecnologia, Avinguda del Canal Olímpic, s/n, E-08860 Castelldefels, Barcelona, Spain. E-mail: marta.agudo@ideg.es
4. Institute of Geomatics, Parc Mediterrani de la Tecnologia, Avinguda del Canal Olímpic, s/n, E-08860 Castelldefels, Barcelona, Spain. E-mail: oriol.monserrat@ideg.es
5. Professor, Dept. of Earth Sciences, Univ. of Milan, Via Cicognara 7 I-20129 Milan, Italy. E-mail: bruno.crippa@unimi.it