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3D MODELLING OF THE ACROPOLIS OF ATHENS USING BALLOON IMAGES AND 
TERRESTRIAL LASER SCANNING 
V. Tsingas 3, , C. Liapakis b , V. Xylia 3 , D. Mavromati c , D. Moulou c , L. Grammatikopoulos a , C. Stentoumis 3 
a Elliniki Photogrammetriki Ltd., Ipsilantou 66, 15121 Pefki-Athens, Greece - (vassilios.tsingas@elpho.gr, 
lazaros.pcvg@gmail.com, christos.stentoumis@gmail.com) 
b Geotech O.E., Perikleous 41 and Thetidos 2, 15344 Gerakas-Athens, Greece - cliapakis@geotech.gr 
c Greek Ministry of Culture, Acropolis Restoration Service, 10 Polygnotou Str.. 10555 Athens, Greece - 
(mavromatid@yahoo.com, thmoullou@hotmail.com) 
Commission V, SS/19 
KEY WORDS: 3D Modelling, DSM, True Orthophotos, Close-Range Photogrammetry, Terrestrial Laser Scanning, Balloon, 
Cultural Heritage, Athens Acropolis 
ABSTRACT: 
The paper focuses on a description of the techniques, both photogrammetric and geodetic, used for the data acquisition and 
processing concerning the project “Development of Geographic Information Systems at the Acropolis of Athens”. Aiming at the 
development of a Geographic Information System which will incorporate large-scale orthophotomosaics for the walls, an 
orthophotomosaic of the top view of the site, as well as a dense textured 3D surface model of the walls along with the rock, the 
project is divided into three basic tasks: the geodetic, involving field measurements for the generation of a polygonometric network 
and terrestrial laser scanning of the walls along with the Erechtheion monument, the photogrammetric one involving image 
acquisition, orientation, DSM generation and orthorectification, and finally the development of the GIS. This contribution underlines 
particularly the methodologies applied highlighting simultaneously the potential of combining photogrammetry and state-of-the-art 
geodetic techniques (laser scanning) for an accurate 3D modeling of cultural heritage sites. 
1. INTRODUCTION 
The geometric recording of one of the most important 
archaeological sites worldwide, the Acropolis of Athens, is a 
challenge for any surveyor and researcher in the field of surface 
modelling. The current work is part of the project 
“Development of Geographic Information Systems at the 
Acropolis of Athens”, financed by the European Union and the 
Government of Greece, and supervised by the Acropolis 
Restoration Service, Hellenic Ministry of Culture. The partners 
in this project are Elliniki Photogrammetriki Ltd (Elpho), 
Athens, Geotech O.E., Athens, ETH (Swiss Federal Institute of 
Technology), Zurich, National Research Council, Canada, 
Institute for Mediterranean Studies, Foundation for Research & 
Technology (FORTH), Rethymno, Crete, with external 
cooperators, Leica Geosystems, Switzerland and Basis Software 
Inc., USA (see Moulou and Mavromati, 2007). 
The project started in June 2007, will finish end of 2008 and its 
goals can be summarized as follows: 
• Establishment of four new trigonometric points (combined 
with the three old ones) covering the whole monument. 
• Establishment of a new polygonometric network. 
• Production of true orthophotomosaic at a scale of 1:50 (pixel 
size 5mm) of the north, west, east wall façades. 
• Production of true orthophotomosaic at a scale of 1:25 (pixel 
size 2mm) of the wall areas, where significant, ancient 
architectural members exist that were built in the wall (areas 
of special interest). 
• Production of true orthophotomosaic at a scale of 1:100 (pixel 
size 10mm) of the top view of the hill and generation of the 
necessary Digital Surface Model (DSM) of the hill. 
• Production of full 3D surface models (and phototextured 
surface models) of the rock, the walls (outer and inner) and 
Erechtheion derived from 3D laser scanning at a resolution of 
lcm for the areas of special interest, 5 cm for the rest of the 
walls, including its interior façades and 0.5 cm (or even better 
where it is needed) for the Erechtheion. 
• Development of a GIS based on the above-mentioned 
orthophotomosaics and other geodata and the existing 
architectural plans, aiming at constituting a valuable 
documentation and restoration management tool. 
• Connection of the GIS with the upgraded documentation 
database and publication on the Internet. 
Undoubtedly, most of the above deliverables are basic 
photogrammetric products, denoting the importance of 
photogrammetry and terrestrial laser scanning in the 
geometrical and textural documentation of archaeological 
monuments. 
In the last years, photogrammetry has incorporated new 
technologies capable of sampling large amount of surface 
points at very fast rates, indicating its synergy with range-based 
modelling, as an essential demand in heritage documentation 
and conservation applications. The fusion of the 
aforementioned techniques overcomes significant problems 
concerning especially the manual collection of 3D points with 
stereoscopic viewing, which is a time-consuming process and 
* Corresponding author, vassilios.tsingas@elpho.gr.