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NEW FRONTIERS TO ARCHITECTURAL SURVEY:
LASER SCANNER 3D
Prof. L. Andreozzi *, L. Barnobi *, A. Giuffrida *, C. Santagati*
* University of Catania, Engineering Faculty, Dept. Of Architecture and Town-planning, Lab. of Architectural
Photogrammetry and Survey, Viale A. Doria,6 — 95125 Catania, Italy luigi. andr eozzi@tin.it
1. GENERAL REMARKS ABOUT
ARCHITECTURAL SURVEY IN ITALY
In each intervention heading to knowledge, cataloguing,
conservation, recovery and exploitation of the environmental
and architectural ass ets, survey is a catalysing element.
I is a "reconstruction" of the assets, through different ways of
enquiry (mensoria, historical-critical, archival, bibliographical,
technical, technological), carried out with different criteria and
proceedings, through the analysis of the reasons for its coming
into being with the passing of time.
Concerning the existing situation, the scientific debate is
focused on the distinction between surveying and survey since
we mean by the first one the measuring aspect and by the
second one the accumulation of the analysis and studies that
have been dealt with by different disciplinary spheres (see also
the final note drafted and approved by the partecipants at the
Congress in Rome about “Document on Architectural Survey”).
For years, surveying has been assigned to specialized architects
and éngineers’ ability and experience, and its transcription has
been expressed through not coded graphical forms, which aim at
a representation that will be closer to iconic art than to science.
Nowadays, surveying operation must document the metrical
completeness of grafic data, of those concerning diagnostics,
etc. It follows that surveying must have an hypothesis of
scientific nature, based upon experience and, therefore , upon
experiment repetitiveness.
Anyone who is interested in monuments’survey, or generally in
architectural and building heritage, knows well what the survey
operation's value and meaning are. He knows how much
engagement is required and how many hours of hard work on
site are needed to survey, elaborate the data, verify and re-draw
a plan, a façade, a cross-section.
The bi-dimensional representation method, with grafic
transcription on paper sheet, is a system which is infected by an
abstracting operation with reference to the real perception of an
As professor Miglian says ^...perché - il rilievo - lo sia, € necessario
che tutto l'iter della sua formazione, dalle prime ipotesi progettuali fino
al risultato finale, sia accuratamente documentato; in altre parole non
possiamo piü ammettere che il rilievo si riduca a una ricca serie di
disegni, ma deve consistere anche nelle misure effettuate, negli
algoritmi applicati alle misure per dedurne le quantita,
nell'esplicitazione degli errori residui (vedi incertezza), nella distinzione
tra le parti osservate con l'ausilio degli strumenti..." (*...it is necessary
that the whole passage of its [survey] forming, since the first project
hypothesis to the final results, would be precisely documented, so that it
[survey] will be scientific; in other words, we cannot admit any more
that survey merely consists of a rich sequence of drawings, but it has to
be composed of effected measurements, of algorithms applied to
measurements in order to deduce ther amount, of residual error's
explicitness, of differenoe among the parts observed by instrumental
aid.."). C£.. Migliari, R., 2000. Principi teorici e prime acquisizioni nel
rilievo del Colosseo. In Disegnare, idee, immagini, A. X, n. 18/19.
object, so that we aim at replacing it by other survey methods
that also allow the 3D representation of the work.
Nowadays, on the other hand, there is a great demand for
survey's result to be acceptable, free from uncertainties, and in
accordance with a quality certification (ISO regulations).
Computers permit a survey proceedings transformation, a
metamorphosis which corresponds to the different forms of
digital, analytical and analogical reproduction, that tends
towards the objects and architectural buildings documentation
and cataloguing.
A proof of that is the operating methodology, that enables to
document a building in toto or partially, by using digital and not
digital images, by putting them together, using the rules of
stereoscopy applied to photogrammetry to build one 3D model.
Then, if it is possible to pass from a stereoscopic model to
another one, the result will be the Digital Continuous Model, a
3D reading model, that allows the metrically accurate
reproduction of the object, measurable point by point. This
model can be explored by means of a computer, an active screen
and a pair of passive glasses.
At the present time, these systems are supplemented with the
laser scanner 3D. This is an instrument that employs two
combined methodologies: the first one based on diastimeters
which aim at obtaining the measurement of distances, and the
other one based on scanning.
Thinking of surveying a monument as great as Colosseum by a
traditional method might dishearten you because of the
operations’ complexity, whereas, if the methodology applied is
the scanning one based on a polarized laser light ray, it is less
complex than you can expect it to be. The “pencil” of rays flows
across the whole surface and captures, point by point, its polar
co-ordinates which are afterwards turned into Cartesian co-
ordinates, having their starting point in the loud station one.
The 3D modelling concept is more and more employed in
architectural objeds surveying and descriptive operations. An evident
example of that is the modelling of the villa described by Vitruvio.
Compare. Mezzetti, C., 2001. Trenta anni di Disegno nelle facoltà di
Architettura e Ingegneria. Edizioni Kappa,;Taus, P., Mezzetti, C., Clini,
P. 21-23 september 1995. La basilica di Vitruvio: disegno della
Memoria. In Disegno luogo della Memoria. Proceedings of the
International Congress, Florence; by the same authors 1995.
L'architetto Vitruvio e la basilica di Fano, segni disegni di un'opera
unica. In Disegnare, idee, immagini, A. VI, n. 11. The interest in this
method of description is documented in various studies, articles and
experiences from various congres ses.
We are talking about new digital tecnologies which permit to pass
from a stereoscopic model to the following one setting together the
single stereoscopic models which can be explored without solution of
continuity .Cf. Migliari, R., 1997. Il modello digitale continuo. In
Disegnare. Idee, immagini. A. VIII, n. 15, and. Santagati, C., 16 — 18
november 2000. La sperimentazione del moddlo stereoscopico continuo
per la documentazione, conoscenza e misura dei sistemi voltati. In
Proceedings of International Congress, // rilievo dei beni architettonici
per la conservazione, Rome.
