IMAGE-BASED 3D MODELING OF THE ERECHTEION, ACROPOLIS OF ATHENS 
Fabio REMONDINO U2 ’ *, Sabry EL-HAKIM 3 , Emmanuel BALTSAVIAS *, Michel PICARD 3 , Lazaros 
GRAMMATIKOPOULOS 4 
1 Institute of Geodesy and Photogrammetry, ETH Zurich, Switzerland- (fabio, manos)@geod.baug.ethz.ch 
2 3D Optical Metrology Group - Centre for Scientific & Technological Research (IRST), Foundation B. Kessler, Trento, 
Italy 
National Research Council Canada, Ottawa, Canada - (Sabry.El-Hakim, Michel.Picard)@nrc-cnrc.gc.ca 
4 Elliniki Photogrammetriki Ltd. (Elpho), Athens, Greece - lazaros.pcvg@gmail.com 
Commission V, Special Session SS-19: Recording and documenting the Acropolis of Athens 
KEY WORDS: Image-based Modeling, Photogrammetry, Matching, Cultural Heritage, Erechteion, Athens Acropolis 
ABSTRACT: 
In this contribution, we report on the image-based modeling (IBM) results of the Erechtheion monument, located inside the 
Acropolis of Athens, Greece. The work is part of the project “Development of Geographic Information Systems at the Acropolis of 
Athens“. An aim of the project is the 3D documentation of the whole Acropolis, one of the major archaeological sites world-wide 
included in the UNESCO World Heritage list. The largest part of the monument was digitised with laser scanning, while the main 
objective of IBM was to model difficult-to- access areas not covered by the scanner but also for comparison with laser scanning for 
scientific investigations. For the 3D modeling, as the Erechtheion contains some typical architectural elements (like columns, flat 
walls, etc), some manual measurements were necessary. On the other hand, for some detailed areas automated approaches for dense 
surface reconstructions are applied. For these parts we compared the image matching results with the surfaces coming from a laser 
scanner. 
1. INTRODUCTION 
The digital documentation of cultural heritage monuments and 
sites is receiving great attention in the last decade and 3D 
modeling of objects or sites is one of the main research topics in 
this field. The employment of computer technology to create 
digital archives of cultural heritage and artistic objects with 
different characteristics and dimensions (monuments, 
archaeological sites or finds, architectural features, etc.) is due 
on one hand to the availability of new technologies for 
digitalization and investigation purposes and, on the other, to 
the increased interest of archaeologists and restorers to find an 
advanced system able to provide innovative investigations and 
documentations. 
two methodologies are also integrated within the project but in 
this contribution we only report about the image-based 3D 
modeling of the Erechtheion monument. 
We present and discuss the problems and challenges of data 
capturing, processing and model generation when dealing with 
a large complex structure with data acquisition under time 
constraints and adverse conditions. 
1.1 Brief historical background 
The following description of the Erechteion story is based on 
the WEB site of the Greek Ministry of Culture 
(http://odysseus.culture.gr/h/2/eh251 ,jsp?obj_id=973). 
Indeed, many improvements have been done in the generation 
of digital models of monuments and artifacts, using range 
sensors or IBM. But there are still a lot of open questions arid 
problems in deciding which technique should be employed in 
which situation. While in the past years, when high level of 
detail was required, range sensors were usually preferred to 
image data, nowadays, due to the considerable algorithm 
improvements and increase of automation in the image-based 
modeling process, the digitization of cultural heritage based on 
close-range photogrammetry is a viable alternative. 
This work is part of the project “Development of Geographic 
Information Systems at the Acropolis of Athens“ (Moullou and 
Mavromati, 2007). Within this project, one of the aims is the 
generation of a textured, high-resolution, accurate 3D model of 
Erechtheion and a respective movie. The work is done in 
parallel with image and range data (El-Hakim et al., 2008). The 
Erechtheion (Figure 1) was erected in 421-406 BC as a 
replacement of an earlier temple dedicated to Athena Polias, the 
so-called “Old temple”. Its name derives from Erechtheus, the 
mythical king of Athens, who was worshipped there. The 
building owes its unusual shape to the irregularity of the terrain 
- there is a 3m difference in height between the eastern and 
western parts - and the multiple cults it was designed to 
accommodate. The sanctuary also contained the grave of 
Kekrops and the traces of the dispute between Athena and 
Poseidon for the possession of the city of Athens. The temple 
was made of Pentelic marble, the frieze of Eleusinian grey 
stone with white relief figures attached to it and the foundations 
of Piraeus stone. On its east side, an Ionic portico with six 
columns sheltered the entrance to the east part of the building. 
On the north side is the entrance to the west part of the building, 
sheltered by a pi-shaped propylon with four Ionic columns 
Corresponding author. 
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