NOTES ABOUT TOPOGRAPHIC AND PHOTOGRAMMETRIC SURVEYING
FOR THE INVESTIGATION OF THE DOME BEARING VERTICAL WALLS
IN S. MARIA DEL FIORE CATHEDRAL OF FLORENCE
P. Aminti, I. Chiaverini, D. Ostuni (University of Florence)
ISPRS - Commission VI - Work Group 3
KEY WORDS: S.Maria del Fiore, photogrammetry, geometry, topographic survey
ABSTRACT
The purpose of the present paper is to discuss the results of topographic and photogrammetric surveying and of numeric
and graphic elaboration of data, in order to give a contribution to the geometric researches on the cathedral carried out
by the University of Florence. The authors analytically report methods and obtained precision in the various phases of
surveying and a synthesis of geometrical results.
INTRODUCTION
This study has been carried out in the laboratory of
topography and photogrammetry of the civil engineering
department (DIC) in the University of Florence and is a
part of a complex research plan which includes other
laboratories and departments, the University of Pisa, the
Opera del Duomo, the Soprintendenza for architectural
and artistic monuments of Florence, the military
geographic institute (I.G.M.I.).
The first aim of this study, which began in 1992, was to
determine the variations from vertical geometry, of the 4
internal bearing walls located in the diagonal sides of the
octagon at the centre of the Latin cross plan. The
concurrence of scientific interests and the many studies
carried out on the cathedral of S.Maria del Fiore and its
great artistic evidence, brought the authors to consider the
opportunity of a further analysis, based on the same data,
but in a different perspective.
So stereopairs and tie points were again used, in order to
determine the global geometry of the octagonal prism
generated by the 8 lines laying on the vertical corners
under the intersections of the sails of the frescoed vault.
The authors are still carrying out further measurements, in
order to complete the current analysis and to permit a
linking and a new valuation of the results of various
studies, beginning from the Ximenes's (1700), and going
on with the more recent surveying of 1934 (Opera del
Duomo), the works of Fondelli et al. (1975) and the
geometric high precision levelling carried out by IGMI
(1986, 1992) for the Soprintendenza for architectural and
artistic monuments of Florence.
The present paper reports the methods and the first
results of this new study. There are some interesting
evaluations of irregularities which have been considered of
importance for static analysis of structures and for
historical research on the building.
1 - TOPOGRAPHIC SURVEYING OF THE TIE POINTS
1.1 - Instruments employed
A Geotronics 440 total station was employed both for
angular and linear measurements, in framing survey and
in the tie points determination. Iron plates and basements,
which supported both the instrument and the signal- prism
unit, were used for the forced centering of the station
points. In order to have an adequate precision in angular
measurements, on the basis of other experiences, we put,
on the prism unit, a low distance suitable target ( we had
side lengths less then 14 m)
1.2 - Station and tie points materialization
Station points were placed on the baluster of the first
gallery, at the elevation of about 30 m from the floor of the
cathedral. Their materialisation was carried out by IGMI
(geographical military institute) by means of spherical
head stainless steel bolts with an axial blind hole for
precision centering.
For tie points materialisation, 10x10 cm wide paper bench
marks were designed and glued to the walls. The shape
of the target had been just tested for precision angular
determinations, at variable (from 20 to 60 m) distances
and we verified their fairness in stereoscopic collimation
during stereocompilation.
