3 Cavulli, F. Grimaldi, S. 2007 To see or not To see: archaeological data and surface visibility as seen by an AIS (Archaeological Information System) approach Figueredo, A., Velho, G., Proceedings of the XXXIII Computer Application and Quantitative Methods in Archaeology Tomar, Portugal CAA Portugal 413-422 21-24 March 2005 visibilità, superfici, sistema informativo archeologico