CIPA 2003 XIX th International Symposium, 30 September - 04 October, 2003, Antalya, Turkey 
instruments, show "geometric anomalies" that don't 
have a logic explanation but simply depend from the 
uncertainty of past tracings. 
Survey in this case reproduces of the state of fact, pure 
knowledge through representation. 
Today science and technic are not separated and 
autonomous anymore, but they are more and more 
interconnected. 
Measure is the support of this exchange. 
The quantitative knowledge of the architecture, 
consisting in its measurement through the survey and 
subsequently through its representation, leads to the 
model that can be considered a sort of image of the 
state of fact to which in these centuries, different 
projects and stratified realizations concurred in a 
chaotic order. 
1.3 Survey and representation 
The different spatial dimension of survey requires 
different methodologies, precise solutions, and 
adequate instruments. 
Unlike territorial representation, that cartography well 
supports and where planimetry is in general privileged, 
in architecture each of three spatial dimensions (X,Y,Z) 
have an equivalent importance. In general, unlike 
territory, the architectures have an inside and an 
outside and the survey for the inside often requires 
different techniques and instruments from those 
necessary for the outside. 
San Lorenzo makes this distinction ephemeral because 
the outside seems an inside (niches, undercuts, 
recesses..) and the inside space is composed by solids, 
vacuums, volumes at different heights that render the 
survey difficult independently from the used instrument. 
Therefore an external and internal grid reference 
system on different levels of the monument that allows 
to supply references to its constituting parts in a unique 
system is necessary. Thicknesses, distances, volumes, 
trends, surfaces are in this way rebuildable starting 
from the simple differences of spatial coordinates. 
Survey methods can't leave out of consideration (San 
Lorenzo is the validation in the field) the "banal" 
methods of direct measure, despite of the 
sophistication of the current technology. 
The object is shattered in a set of punctual 
characteristic points such that their possession leads us 
to the knowledge of the masterpiece in its wholeness. 
The transfer of typical methods of the cartographic 
survey to architecture, hoping of obtaining for analogy 
the same results achieved in cartography, is not a 
practicable path without correctives and principles of 
validation. In fact surveying architectures, the 
correlation between the purpose of the survey and the 
elements to survey, not only is much more selective 
and discriminant but also more subjective. It is true 
that some type of homologation, at least in the most 
diffused scale, 1:50, has been used (vide the first 
specifications), but, as usual, foreseeing all the 
following necessities is very difficult especially when 
problems come out one after the other, caused one by 
the other. 
The discretization in points of survey highlights the 
entire problematic limitation of the method, and the 
curious thing is that, while not long ago the problem 
seemed to find its limit in the scarcity of points 
necessary to represent the structure of an architecture, 
today it's the opposite with the scanning-laser. 
Obviously the photogrammetrical method survives and 
it is not disjoined, at least in part, from the applications 
of the new methods admitted by the instruments and 
the computer science. 
1.4 Forms of bi-dimensional and three- 
dimensional representation 
There is a consolidated tradition on how to represent 
graphically on a plan the three-dimensional objects, but 
there isn't a consolidated tradition on how to represent 
them graphically on a three-dimensionally plan. But it is 
immediately necessary to specify that when you enter 
in the three-dimensional field, the photogrammetry is a 
sharer technique, with the others, to achieve the final 
result. It's clear that here for 3D we mean those shapes 
that can have an effective and three-dimensional 
representation (i.e. in the bi-dimensional representation 
on video or on paper, the points that I see are affected 
by three coordinates and therefore their position is 
known in the assumed reference system), observable 
from different points of view once the model of reality 
is carried out. 
Whether the model is obtained through the 
photogrammetrical method in some cases, or through 
new methodologies based on the acquisition in short 
times of clouds of points of the object in an opportune 
system of reference, the problem of the representation 
of the object always remains. 
Basically one of the most important advantages of 
using the photogrammetrical system is that it has 
already been tested many times, therefore it produces 
extraordinary results where it is practicable and 
convenient, whether generating vector representations, 
or raster ones (photoplans) when possible, or the ones 
usually called 3D orthophotos. These last ones which 
need the construction of the DSM (Digital Surface 
Model), which can be partially computerized, work out 
the model dressed with the orthorectified digital images 
of the surfaces. 
The laser scanner system creates the image of the 
model using millions of points, the so called cloud, but 
it is a representation that can't be used by itself. It 
must be depurated from the abnormal points using 
sophisticated algorithms because of their high 
numerosity. These algorithms have not yet been 
adequately tested on big numbers and are run through 
software packages created for other purposes and only 
recently present versions that help solving this problem. 
Once you obtain the "dean cloud"of points, difficult to 
achieve in complex cases like San Lorenzo, you can 
start the research of three-dimensional representation. 
1.5 Survey Grid Reference 
Photogrammetry, in its classical feature or in the new 
digital othoprojective one, needs the aid of the essential 
topographic operations on the territory. These are 
made up of a highly precise reference grid that 
embraces entirely the monumental architecture; it 
builds up the frame within which all the survey 
develops, and its purpose is to stop the propagation of 
mistakes proceeding from general to particular views 
and it is characterized by permanent reference 
vertexes.