3D MODELS GENERATION FROM LASER SCANNER DATA TO SUPPORT DIGITAL 
ORTHOPHOTO 3D: 
The mosaic surface of the floor of S. Marcus Basilica in Venice. 
Carlo MONTI 
Full Professor, DIIAR Director 
E-mail: direz(g)idra5.iar.polimi.it 
Professor 
Carlo SAVI 
EP - Technician 
E-mail: carlo@topo.polimi.it 
Raffaella BRUMANA 
E-mail: brumanar@ idra5.iar.polimi.it 
Luigi FREGONESE 
Research Assegnist 
E-mail: luigi.fregonese@polimi.it 
Cristiana ACHILLE 
E-mail: achillec@idra5.iar.polimi.it 
zu year Course of Doctorate 
DIIAR - Department of Hydraulic, Environmental, Street Infrastructures and Survey Engineering 
Survey Division - Polytechnic of Milan - ITALY 
Laboratory of "Survey, Digital Mapping and GIS” 
P.za Leonardo Da Vinci 32 - 20133 Milano - ITALY 
tel. +39 2 2399 6533 fax +39 2 2399 6550 
The research has like purpose the realization of a 3D digital Orthophoto Map of the floor at the scale of the 'tessera' (1:5 and less) in 
order to support an advanced GIS for the documentation, maintenance and restoration of mosaic surfaces in the architectural yard of 
the Basilica. 
It has been experimented modern systems of survey Laser Scanner (Callidus 3D Laser System) in order to realize a Digital Surfaces 
Model (DSM) and acquisition of the photogrammetric takes with high resolution Rollei D7 metric camera. 
The obtained DSM will come compared with different that one obtained for auto-correlation with software of digital 
photogrammetry. 
KEY WORD: Survey, Digital Photogrammetry, Laser Scanner, 3D Digital Orthophoto, DSM. 
The impossibility to systematically apply methods of digitally 
rectifying the "at risk" objects and contexts, while quite 
common, has caused the professionals involved in the risk map 
to prepare a valid raster/vector support. Unfortunately, however, 
rectification is not always applicable when it becomes necessary 
to maintain the evolved historic 3D progress, associated with 
flooding problems and issues of floodwater drainage. 
In particular, our research aims to develop a methodology for 
generating surfaces, adapted to surface theory, integrated into 
interpretation and interpolation techniques and adapted to the 
issue of architectonic modelling. 
In this aspect, our research will explore the following issues in 
the scope of the survey through: 
acquisition of high-resolution laser scanner data on the "At 
risk" objects and complexes, selected as test areas; high- 
resolution digital photogrammetric shots; 
calibration of the shots and the camera; analysis of the digital 
thermographic image warping; 
processing of 3D models of the different surfaces developed 
on different platforms (StudioTools, Mensi, Spider,...) on two 
levels: for finished elements (vectorial mesh exportable in 
DXF standard format) and for analysis of more developed and 
complex surfaces (developed in advanced modellation 
platforms, generated by families of curves) 
handling and intelligent filters for rough models; 
- models and methods of interpretation, analysis of the 
discontinuity of the architectonic elements; generation of 
automatic and semi-guided 3D models; extraction, integration 
and generation of breaklines; 
- interpolation based on surfaces and objects; 
- construction of complex surfaces beginning with simple, 
complex, and isoparametric curves (NURBS); 
*mathematical surfaces constructed on edge curves (of various 
types and degrees) and cloud points; extraction of "on 
surface" curves; 
- boolean operators for generating surfaces starting with 
primitive 3D; 
- implementation in photogrammetric software of processing 3D 
digital ORTHOPHOTOS starting from models: solving 
interface and compatibility issues of the formats, import and 
export of data and models; in particular: 
3D orthophotos of architectonic elements (vaults and 
continuous mosaic surfaces);3D orthophotos of façades, 
curtain walls and elevations on squares, with strongly 
continuous solutions and to different scales, from the 
architectonic to the urban; 
- structuring of the support data of how the interventions fit 
together and risk analysis by the multidisciplinary offices in 
charge of protecting cultural heritage. 
Two experiments have been planned and are already in 
definition phases, based on the official cooperation with the 
Procuratoria di San Marco. 
CONTEXT OF THE “MARCIANO” BASIN (Facades, squares, 
canal banks, canal front walkways,...) and “BASILICA DI 
SAN MARCO”. 
The impossibility to systematically apply methods of digitally 
rectifying the "at risk" objects and contexts, while quite 
common, has caused the professionals involved in the risk map 
to prepare a valid raster/vector support. Unfortunately, however, 
rectification is not always applicable when it becomes necessary 
to maintain the evolved historic 3D progress, associated with 
flooding problems and issues of floodwater drainage. This is the 
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