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LASER SCANNING AND CLOSE RANGE PHOTOGRAMMETRY: TOWARDS A
SINGLE MEASURING TOOL DEDICATED TO ARCHITECTURE AND
ARCHAEOLOGY.
Pierre Drap 3 -’, Matteo Sgrenzaroli b , Marco Caneiani c , Giacomo Cannata 0 , Julien Seinturier 3
a MAP-GAMSAU umr CNRS 694, Ecole diArchitecture,l 84 avenue de Luminy, 13288 Marseille Cedex 09, France
(Pierre.Drap, Julien. Seinturier)@gamsau.archi.fr
b TOPOTEK Centro di Competenza per le tecniche di Rilevamento e la Geomatica via Branze 38, 25123 Brescia Italy
sgrenzaroli@topotek.it
c Laboratorio di ì Rappresentazione Grafica!, ROMA, Università di Roma tre. Italy (canciani,canata)@uniroma3.it
KEYWORDS: Laser Scanning, Photogrammetry, Multisensor, Archaeology, Architecture, Representation, Knowledge Base,
Texture
ABSTRACT
We present here the first steps towards the development of a tool for architectural and patrimonial survey which combines the laser
scanning techniques, close range photogrammetry and a fine analysis closer to the studied field, here architecture and archaeology.
The present work is the result of a join cooperation between, INN.TEC.srl, an Italian Innovation Technology Consortium, with a
Center of Competence (Topotek) specialized in geomatic problems and in particular in the treatment of cloud of 3D points coming
from Laser scanner, a French CNRS laboratory working on close range photogrammetry in the context of architecture and
archaeology and a laboratory from the university of Rome III, specialized in the representation of architecture.
We present a knowledge based survey tool which combines mixed means of Laser Scanner and photogrammetry measurement.
The statement is articulated in three phases:
• Laser scanner allows to model objects in 3D with a density of measurements that cannot be acquired within a reasonable
time frame with traditional technologies. The programme used for laser data management creates a triangular 3D model
(mesh) from the range information and maps 2D information on the 3D model to create the final result.
Generally laser scanning requires to view the surveyed object from several viewpoints to resolve shadows and occlusions
but displacement of the laser sensor is not always easy to achieve on site
• We developed a similar approach in photogrammetry which, using some photographs taken without too many constraints,
can supplement the occlusions or lacks from the laser measurements. A survey based on an approximate geometry of the
object and autocorrelation makes it possible to obtain automatically an irregular mesh with appropriate texture. The
orientation phase uses the data provided by the scanner to orient the photogrammetric measurement in the same set of axes.
• The last phase involves the use of an expert system based on a knowledge representation of the object measured in order to
rebuild an architectural or archaeological object while being based to the taken measures and an elaborate ideal model in
collaboration with the architects or archaeologists.
The work presented here is based on an experimental study of an Etruscan amphora found on the Grand Ribaud F wreck, in HyEres,
France, and studied by Dr. Luc Long, Cultural Heritage Curator, DRASSM, Marseilles, France. The survey took place at the
University of Rome III in the laboratory of architectural representation directed by Prof. Diego Maestri. The laser scanning was
made with the Callidus sensor gracefully lent by the company Geosystem group, Roma.
After this debugging phase on a simple object as an amphora, we project to extend this method for architectural survey.
1. INTRODUCTION
The main objective of architectural and patrimonial survey is to
provide a precise documentation of the status quo of the
surveyed objects (monuments, buildings, archaeological object
and sites) for preservation and protection, for scientific studies
and restoration purposes, for the presentation to the general
public.
Complex object, not planar or with ornaments and decoration
require high-density and high-resolution spatial data.
The laser scanning techniques and close range photogrammetry
can offer two complementary sets of instruments and
technologies capable to answer to the specific requirements of
architectural and archaeological survey.
Laser scanner technology is based on active range sensors
measuring directly the distance between the sensor and points
over the surveyed object. Photogrammetric technology is
generally based on processes of recording, measuring, and
interpreting photographic images (passive sensor).
Several aspects can be considered comparing the two
technologies:
i) Acquisition time is generally fast with photographic
cameras but longer and sometimes manual work needs do
be done for extracting dense 3D measurements from
stereoscopic pictures. Laser scanner acquisition time can
vary from scanner type up to a maximum of c.a. 30
minutes (for a single range scan) with the advantage of
providing directly 3D measurements.
ii) Resolution is generally limited for laser sensor depending
of type of sensor and generally decreasing with the
increasing of scans range and spatial coverage. With high-
resolution digital or analogical photos high-accurate
measurements can be obtained
iii) Shadow and occlusion problems during acquisition phase
can be solved through photogrammetric acquisition easier
than planning many laser scanning acquisitions
