A totally new chapter in the photogrammetric survey of architectural 
monuments was recently written using electronic data processing on 
the study of the intrados and extrados profiles of the meridian ribs 
of the dome of Santa Maria del Fiore in Florence (1). 
The numerical plotting are indispensable wherever one looks for para- 
meters, modules and predominant inclines. The plotting can furthermore 
constitute a very valuable source of data of a statistical nature on the 
state of conservation of the monument in question. 
Processing the numerical coordinates X, Y, Z in timely series of chosen 
points located on the intrados and extrados of the meridian ribs of 
the dome of Santa Maria del Fiore, it was possible to reach, with 
computer, those equations which analytically define the profiles of 
these ribs, and effect a critical inspection of the monument itself which 
was far more complete than one might have logically hoped for. 
In effect, the photogrammetric survey in question has pointed out the 
irregularity of the octagonal drum of Brunelleschi’s dome, of the incli- 
nation of the dome’s geometrical axis of symmetry (about 16’) of the 
eliptic form of the intrados profiles (eccentricity 0.48) as well as of the 
extrados profiles (eccentricity 0.66) of the intersections of the spreaders 
(mid-sections). 
But the most striking aspect of the application of numerical methods 
in the critical interpretation of an architectural monument is undoubted- 
ly that which refers to the statistical analysis of the various numerical 
values observed. 
Applications of spectral statistical analysis currently in the process of 
being published (6) have in fact permitted us to realize that the profiles 
studied in the monument of the Brunelleschi dome present recurring 
discontinuities in the upper sections. These discontinuities appear to 
occur at regular intervals of about 7.5 m in height or, as expressed 
in the ancient florentine unit of measure called « braccia a panno », 
the equivalent of about 12% « braccia a panno ». This last value 
is of great interest for the constructive interpretation of the famous 
monument. 
It is nevertheless noteworthy that the analytical development of the 
observed data presents no limitations of any sort, especially if done with 
instruments of statistical analysis. It has in any case a degree of sensi- 
bility which for the moment is undeniable: the qualities of the photo- 
graphic images. 
Photogrammetric instruments and tecniques for photogrammetric survey 
can today guarantee sufficiently the nearly intact conservation of the 
informational contents of the stereoscopic couples obtained from time 
to time. Further progress in photographic techniques can surely amplify 
the application of photogrammetric methods also in the field of testing 
and periodic checks of these and other more complicated architectural 
structures.