be make denser depending on requirements. 
Nowadays, instead, using ot total stations furnished with 
a diastimeter without reflecting prisms (and therefore 
eliminating burdensome task of signalling the point with 
target reflectors), it is possible to acquire the same data 
directly in the field. 
Differently from a model created by oriented couples of 
photograms on which it is easy to repeat the 
measurements, a topographical determination of the 
cylindrical coordinates of the points imposes an accurate 
plan of measurement of a detail. In such manner, to run a 
risk of not having the sufficient data to describe the shapes 
or, on the contrary, to have a number of information requiring 
costly and patient work on simplification of the graphic 
design, is being avoided. 
During the recognition process, drafts have been issued 
with points, duly numbered and linked among them; these 
points should lead to a significant line. In the subsequent 
acquisition stage, the possibility of using an identification 
code permitted the pre-management of the data into files 
that group the families of the points and that have been 
memorized at different levels in order to facilitate the 
management in cad programmes. 
File management is fundamental: a subject is described 
by means of the points among which the linear interpolation 
is programmed; a descriptive structure that derives 
therefrom defines wireframe lines, so an operator decides 
what should be in-between the lines. 
The same lines are, therefore, a result of the choices aimed 
at the creation of a model that, as always, is a simplification 
and so a scheme of reality, furnished by a sufficient 
descriptive accuracy in order to respond to the research 
objectives. 
It is advisable to work with a very clear project with regard 
to a data bank that, step by step, is being implemented. 
In an tree shaped organization, for example, it is possible 
to distinguish the lines of different nature: structural, wall 
apparatus, the profiles of ornaments and decorations etc..., 
changing the rules, already consolidated ones, of 
photogrammetric acquisition from the observation of the 
model to observation of the reality. 
Considering a particular geometry of the structure that, for 
each span, occludes the view from the parts of the lines 
that confluence from the subsequent onto the transverse 
arch, the vertices of the traverse (fig.3) have been set in the 
centre of each span of the central nave. From each of the 
measuring stations the profiles of the same have been 
measured while some points of the adjacent ones have 
been used to make a cross reference examination. 
On the other hand, if the advantage of the measuring 
processes with polar consists in independence of the 
individual readings, it also requires a control that in this 
case could be easily made by repeating the measurements 
of the adjacent point station that guarantees the accuracy 
of the operations performed. 
For the acquisition of the data, an electronic theodolite 
Leica T 1800 has been used due to its features enabling it 
to measure the azimuthal directions and zenithal angles 
with accura 
that is able 
mm +1 P-P- 
in that way 
the reflecti 
diastimeter' 
the area del 
cone of the 
then, incree 
from 6 mm 
100 m. 
The correct 
small laser l 
A limited dii 
the measuri 
has impose 
angle. 
For the pre 
the variance 
failed to pra 
very inclinec 
the residual 
Figure 4. A view of total acquired data.