CIPA 2003 XIX 1 ' 1 International Symposium, 30 September-04 October, 2003, Antalya, Turkey 
579 
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Secondary grids descend from main ones with the 
purpose of taking coordinates to the interior of the 
rooms where you can place Total Station no-prism 
instruments for tacheometric surveys in order to define 
coordinates of spots on the object, to find its position in 
the reference system in which the main grid has been 
built and to fix visible points on the frames, the so 
called anchor points, in order to orient these to the 
outside. Recently a new logical necessity has been 
pointed out. Every survey must be framed in a single 
reference system and it should have the possibility of 
referring itself to the cartographic national reference 
system (georeferenciation). Georeferenciation is an 
essential step when surveys are part of or are framed in 
a Geographic Information System (GIS). From the 
analytic or digital orientation of the frames we pass to 
the generation of the DSM of the surface. In complex 
cases, especially with a very high number of frames, 
the automatic definition of many points in order to 
correlate different images can be achieved through 
aerial triangulation in order to build the DSM on which 
the raster 3D digital orthophotos can be spread. 
In San Lorenzo it has not been possible to limit the 
survey and representation methods to one single 
technique. It is the typical situation where the most 
modern techniques (laser scanner, digital 
photogrammetry,...) must be mixed up with the ancient 
ones (manual-direct survey). Only through the 
integration of these operative procedures, a complete 
and exhaustive representation of the monument can be 
obtained. 
Figura 1 
1.6 Used instruments, software, mistakes, direct 
integration. 
San Lorenzo survey has been brought out using three 
mechanized theodolites of the last Leica production 
(TCRM 1103, TCRA 1103, TCA 2003), whose precision 
characteristics are well known (several ten thousandths 
of grade for the angular directions and some 
millimetres for the distances). Two of them were 
supplied with no-prism laser diastimeter for 
tacheometric survey of interiors, exteriors, and anchor 
points. The third, the most sensitive on the market, was 
used to establish the grid reference. The whole external 
part and in the intrados of the cupola in the interior 
have also been set out with the LMS-Z210 Riegl laser 
scanner. In the inside the Callidus laser scanner has 
also been used.The software used to process the clouds 
of points are the following: 3D Riscan, 3D Extractor 
(Software owners laser scanner), Spider, StudioTools 
(Alias Wavefront). The uncertainties in specifying 
tacheometric points are always compatible with the 
representation in scale 1:50 (0,2mm graphic error), 
that is the centimetre. Even the exteriors and the 
interiors determined with the laser scanner are 
consistent with this accuracy. The integration with 
measures taken directly with wooden ruler, measuring 
tape, disto, always georefernciated to the tacheometric 
points in the editing stage, has been outstanding. 
The photogram metrical frames in the interior and in the 
exterior of the Basilica have been made with the new 
Rollei db44 Metric digital photogrammetrical camera 
with 16 millions of pixels on a frame of about 
40mmx40mm (1 pixel=9 micron) for the reproduction 
of parts of the Basilica with digital photoplans, where 
possible, and digital orthophotos. 
Figura 2 
1.7 Plans and sections 
To this day the horizontal section at 1,50m of height 
from the step floor has been completed at the nominal 
scale of 1:50. The plan has needed the use of the 
above said instruments, in addition to the definition of 
"eidotipi" (sketches for drawing plans) with the direct 
integration through the use of measuring tapes, 
wooden rulers and distos: everything processed with 
Autocad Map 2000. 
The part of the section that has been surveyed by now 
has followed the same procedure excluding a larger use 
of the laser scanner system, no-prism theodolites and a 
reduction of the direct survey because of the 
inaccessibility of many places. The survey of the 
basement will also follow the same method. 
Some digital photoplans and several orthophotos have 
been made for the exterior part (fig. 2) starting from 
images acquired with the Rollei db 44 metric. The 
photoplans, have been oriented and analytically scaled 
on at least six anchor points. The resolution of these 
frames is precise enough to support the scale 1:50, but 
also 1:20 without loosing definition. Surveying can be 
considered the natural support to the georeferenciation 
of all the different kinds of analysis started 
(mensiochronology, chemical analysis, 
thermoluminescence).