103 
Fig. 3 - Spatial view of the graphic stereoplotting of 
the vault architectural structure. 
tolerances only with medium and large format (from 
6x7cm to 13x18cm) non-metric cameras. The 
mounted lenses must be of high optical quality (not 
always available in low cost systems) and 
furthermore the digital acquisition systems of 
photographic images (drum and flatbed scanners) 
must be of high optical and radiometric resolution 
(>1000 dpi, density range >3,2D). Negative, and 
wide tonal gamma b&w films, have been exposed 
with a UMK 10/1318 metric camera, equipped with a 
wide-angle lens; In many cases settling was made 
leaning the camera directly on the floor in order to 
have enough distance from the object. The frame 
scale was always limited to the value of 1:80*1:100 
to have the opportunity to plot till 1:20 scale with 
accuracy of 1-5-2 mm. 
The difficulties met during the measurement of 
control points have been essentially: 
• the impossibility of executing measures in 
spherical coordinates (angles and distances) 
for the impossibility in the prism positioning; 
• the use of small value vertical angles with the 
consequent difficult collimation and errors due 
to the non verticality of the teodolite primary 
axis; 
• the necessity to collimate only photographic 
points (without targets) on architectural 
elements with repetitive texture as that of stone 
ashlars of masonry vaults, with the consequent 
possibility of gross-errors. 
Some of the mentioned problems could have been 
avoided with the use of no-prism Total-Stations, 
which were not available at that time and that seem 
to be the only instruments capable to speed up the 
leaning operations in such critical condition. 
The vector plotting operations have been carried 
out in a classic analytical instrument Siscam 
Digicart (equipped with 2 pm encoders and 5*18X 
zoom lenses). The operation, carried out by an 
expert operator, required few plotting hours, being 
the photographic images of high quality and with a 
sufficiently schematic reading of the masonry 
texture. The digital plotting phases aim, instead, 
Fig. 4 - Isometric view of D.E.M. generated by 
automatic image matching.