Proceedings 18 th International Symposium CIPA 2001
Potsdam (Germany), September 18 - 21, 2001
INTEGRATED METHODOLOGIES OF SURVEY -
DIGITAL PHOTOGRAMMETRY AND 3D MODEL LASER SCANNING
The Representation of the Piazza San Marco in Venice
Carlo Monti
Full Professor, DIIAR Director
E-mail: direz@idra5.iar.polimi.it
Raffaella Brumana
Professor
E-mail: brumanar@ idra5.iar.polimi.it
Luigi Fregonese
Research Assegnist
E-mail: luigi.fregonese@polimi.it
Carlo Savi
EP - Technician
E-mail: carlo@topo.polimi.it
Cristiana Achille
E-mail: achillec@idra5.iar.polimi.it
2 nd year Course of Doctorate
DIIAR - Department of Hydraulic, Environmental 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
KEYWORDS: Survey, Digital Photogrammetry, Laser Scanner, 3D Digital Orthophoto, DSM
ABSTRACT
Usually representation of a square has been realized trough plans and facades. Modern analysis of evaluation of environmental
impact, urban and planning studies demand 3D models more advanced. The realization of these models demands traditionally high
costs and elevated times of survey and processing of data.
Availability of laser scanning instrumentation could open today immense horizons in the realization of complex models to different
scales and on extensive areas.
For the experimentation the “Piazza San Marco” (Saint Marcus square) in Venice has been chosen for the various views that it offers
to who comes from the sea and to who comes from earth, and also because available and comparable with the previous topographical
and photogrammetric surveys. Takens have been acquired in order to obtain digital ortophoto on the 3D square model.
Here is also summarized the first technical the research realized trough RIEGL Laser Measurement Systems “3D-Imaging Laser
Sensor LMS-Z210”, in order to evaluate the accuracy obtained on control points and profiles and scales carried out on different
case studio and particularly on complex architectural monument such as the San Lorenzo Basilica of Milan.
1. INTRODUCTION
The new instruments to scansion based on laser distance-meter TOF (Time Of Flight = measure of the flight time) allow to obtain in
fast way architecture digital models with acquisition in simultaneous of the radiometric value of the pixel on object. The main
operation consists in measuring distances on the base of the time employed from the light laser in order to hit up target and to behind
return by means of one unit laser to high speed; the measure of the distances is obtained by means of the lines of scansion realized
generally by means of rotating mirrors in continuous with variable angles of opening in dependence of the configurations. The
acquired data is constituted from measure of distance, line scan angle (polar angle) and frame scale angle (azimuth angle),
radiometric information, observations that opportunely modeled allow to obtain the DEM. The study of such methodology has
interested the basin and Basilica of Saint Marcus in Venice, whose architectonic complexity has allowed a valid experimentation in
order to verify reliability of the system and its precision.
Here are experimented new laser scanner technology TOF based, in order to verify application field, metric accuracy and precision
of the point DEM at the different scale of the representation. It has been compared the first results with different methodologies, both
topographic and photogrammetric. Interoperability between survey systems and dedicated software seems to be one of the goals to
be experimented in future. DMS modellation is an open problem, the main problem.
Have been made many laser scanning sessions in all the St. Marcus square with different angle stepwidth, to evaluate effective
precision of instrument. At the same time laser scanning sessions have been made in the interior of St. Marcus Basilica to generate
polygonal model of “Ascensione’s dome” and to evaluate efficiency of 3D sensor in condition of artificial lighting system.
In order to georeferencing all models and semi-metric takens a traditonal topographic survey has been made with no prism total
station LeicaTCRM 1103.
