Laser scanner survey and 3-d modeling of the Cetara tower on the amalfitan coast.

The main goal of this work is to study and experiment the use of the terrestrial laser scanning technique in order to survey an architectural heritage. The experiment concerns the survey and the modeling of a tower characterized by a very articulated plan and a complex geometry placed in Cetara (Amalfitan Coast). We used three different laser scanners: Cyrax HDS2500, Optech ILRIS-3D and Riegl LMSZ420. The surveys carried out with the three different instruments demanded different design, planning and execution of the experiment. In order to carry out the survey of the Tower it has been necessary to run a high number of scans from various points of view and with different resolutions. This was necessary for the correct reconstruction of the architectonic elements which are complex and difficult to bring to simple and linear geometries. Modeling has been carried out using several commercial softwares used to filter the scan results and to reconstruct the 3D model of point clouds and the solid model by means of triangulation. By means of the DTMs derived from the three laser scanners we finally elaborated a number of orthophotos using a digital photogrammetrical software. We started from the images acquired with a semi-metric camera, the Nikon D100; we compared our different orthophotos among them and with that one derived from the DTM obtained by means of digital matching on the photogrammetric stereo pair. Such a comparison was made on a number of common check points.