540 
Baratin, Bitelli, Unguendoli, Zanutta 
3. THE SURVEY OF THE DOME’S INTERIOR 
The survey of the dome’s interior was performed by photogrammetry, using analytical and digital instrumentation. 
It was necessary to overcome some problems, first at all the need to acquire the images from points close to the dome at a 
considerable height in respect to the ground, and questions related to the topographical control survey. 
A tubular scaffold about 12 meters high (fig. 7a) permitted to take the pictures at an height close to the dome base. The topographic 
control survey was realised by a reflectorless Topcon GPT-1000 total station, owing to the impossibility to use artificial control 
points on the frescos. The reflectorless instrumentation allowed to acquire from 4 stations the three dimensional co-ordinates of a 
cloud of points lying on the dome’s internal surface and primarily the co-ordinates of the control points to be used during the 
photogrammetric data processing. The images were acquired by semi-metric cameras with reseau: Rollei 6008, image size 60x60 
nun, and Leica R5, image size 24x36 mm, realising for each dome vault a stereocouple and additional oblique images to provide 
further information (picture example in fig. 7b). 
(a) (b) 
Figure 7: (a) Phase of topographic survey of the dome’s interior; 
(b) example of a Rollei 6008 photogram used for stereoscopic restitution of the dome vaults 
The photogrammetric process was performed using classical high precision analytical instrumentation (Digicart 40 stereoplotter) and 
a digital photogrammetric workstation (StereoView, by Menci Software srl). Starting from a unique reference system, 8 local system 
were defined to realise the restitution phase. In semi-automatic mode a digital object model was realised for each dome vault, 
measuring points distributed on a regular 10x10 cm grid. To complete the models line and polylines along the discontinuities were 
inserted. 
A first product generated was the digital surface model (DSM) for the dome, achieved by linking together the models related to the 
eight dome vaults. The results of the stereoscopic restitution and the derived contour map of the surface are shown in figure 8. 
Figure 8: Stereoscopic restitution (a) and contour map of the dome’s interior surface (b)