The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B5. Beijing 2008 
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on. On the other hand, the term mechanical failure applies 
mainly to material blocks and comprises block fractures (figure 
3), joint dislocations (figure 4), superficial weathering, 
disorganization of major areas due to mortar loss, instability of 
underlain rockmass, and so on. 
The above described structural problems, irrespectively of their 
geometric or mechanical nature, constitute what is typically 
called, the “pathology” of the monument (Egglezos et al., 2008). 
This “pathology” is encountered systematically in large areas at 
the current state of the circuit wall. 
Figure 3. Characteristic fractures in the SE comer of Acropolis 
circuit wall. By D. Egglezos 
Figure 4. South part of Acropolis circuit wall. Characteristic 
dislocations of joints of structural blocks. By D. Egglezos 
Taking into consideration the above mentioned problems, as 
well as the severe loading factors acting on the circuit wall (soil 
thrust, dead load from its own weight, thermal loading, 
foundation instabilities, and -the rather critical load- earthquake 
events), it is easily concluded that a systematic intervention has 
to be launched. The intervention has to assure a) minimization 
of additional deterioration, b) restoration of seriously damaged 
areas, c) drastic decrease of the effect of loading factors and d) 
safe conditions for a long period of time. This intervention, in 
brief, must comprise tasks as, geometric documentation of the 
existing state, realization of supporting studies relating to the 
walls (systematic geotechnical investigation of the area, 
drainage of the superficial plane of the rocky hill, proper 
laboratory program for determination of mechanical properties 
of structural blocks, seismic hazard evaluation study and so on), 
geostructural analyses for interpretation of current state and 
proper choice of geotechnical and structural model simulation 
for design of stability measures (both for the walls and the 
supporting underlain rock), extended instrumentation for 
continuous observation of both the current and future (post 
intervention) state, continuous conservation of the 
repaired/restored monument. 
In this paper, the main emphasis from the above mentioned 
targets focuses on, how rigorous geometric documentation of 
the circuit wall applies directly to geostructural analyses for 
interpretation of current state of deformed sections and permits 
the calibration of structural model parameters. 
3. GEOMETRIC DOCUMENTATION 
Geometric recording based on reliable elevation information 
and 3D phototextured models are now, perhaps, the standard 
photogrammetric products for archaeological and architectural 
documentation (Mavromati et al., 2002, Georgopoulos et al., 
2005). An orthophoto constitutes a powerful textured 
representation combining geometric accuracy with high visual 
quality and a wealth of detail, providing invaluable information 
about morphology and deformation. Hence, it is a non- 
generalized background arid the vectorized interpretation to be 
overlaid is left to the specialists. A fully 3D photo-textured 
surface model provides photorealistic visualization, high 
geometric accuracy and facilitates geometric or morphological 
documentation and analysis (Moullou et al., 2007). 
The recording and the documentation of the Acropolis circuit 
walls is a vital part of the restoration planning. Due mainly to 
its size (~ 760m perimeter, maximum height 18m) and its 
inaccessibility (figure 5) the only fast and accurate method that 
could be applied is a proper combination of photogrammetry 
and 3D laser scanning. 
This is the reason why the Acropolis Restoration Service 
initiated, in 2007, a project, its objective being the recording, 
modelling, visualisation and GIS applications development for 
the Acropolis archaeological site. 
The project has a dual goal consisting of: firstly the production 
of the scientific infrastructure needed for current or future 
restoration planning, with the emphasis laid on the Acropolis 
circuit walls. The project will cater for the investigation of the 
various interventions the walls have sustained across time, for 
the location and study of the poros limestone and marble blocks 
reused in them and for the examination of their static 
sufficiency. And secondly the exposure of all information