Modellazione 3D dell’ambiente urbano mediante integrazione di scansioni laser aeree e terrestri: l’esempio del Castello di Gorizia

In this paper the 3D modeling of the urban-historical environment of the Castle of Gorizia, obtained by integrating aerial and terrestrial laser scans and digital imaging data, is described. The aerial data have been acquired by a helicopter equipped with an Optech ALTM 3033 laser system coupled with a Rollei DB44 metric camera. The laser data have been processed by the TerraScan (Terrasolid) software, making possible the point filtering, the point classification, and the 3D modeling of 355 buildings of the Gorizia downtown. By projecting the aerial images on the DSM laser, thanks to the TerraPhoto and TerraModeler software, the high resolution (0,20 m pixel) digital orthophoto has been produced. For the medieval Castle of Gorizia the integration between aerial and terrestrial data has been carried out: terrestrial scans have been acquired with a Riegl LMS Z360i system laser integrated with a Nikon D100 metric camera. These scans has been mutually registered and globally georeferenced by exploiting reflecting targets, surveyed by total stations from a topographic network. Thanks to GPS differential measures with a Leica System 520 receiver on four network vertexes, the targets (and the scans) have been so directly georeferenced in the Gauss-Boaga cartographic system, the same datum of the aerial surveying. The terrestrial data have been imported in the TerraScan environment, while the aerial ones in the RiSCAN program, so to fine manage the global cloud (36 millions of points) and suitably exploit the software tools to automatically obtain a large number of numerical products as colored point clouds, vector sections and profiles, TIN surfaces, and digital image texturing. Furthermore, all these 3D products have been made available to the user by very realistic virtual navigations, either interactively in VRML or along predefined tours by AVI files. In this way, the user can well study and better exploit the large amount of information so acquired.