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TECHNICAL PROGRESS IN ARCHITECTURAL PHOTOGRAMMETRY 1517 
on the dome of Santa Maria del Fiore are well 
known. Their photogrammetric surveys (ex- 
tended also to other domes of Florence) were 
continued by a statistical analysis of the dif- 
ference between the actual form obtained by 
numerical stereophotogrammetry and the 
theoretical form expressed by the curve 
which, for each groin, passes as nearly as pos- 
sible (i.e., by least-squares) through the 
points plotted. 
Concerning the numerical models of 
monuments, here again it was in Italy that the 
idea was most clearly elucidated by a Floren- 
tine research team (M. Fondelli, E. Cleur, 
and F. Greco). Such models, obtained by 
numerical photogrammetry (either analogi- 
cal or analytical), offer a means for determining 
the essential geometrical features of a build- 
ing, analyzing its profiles and proportions, 
and observing the changes occurring in these 
with the passing of time, with the aid of com- 
puted figures and subsequently expressible 
as a line-drawing either on an automatic trac- 
ing table or on a screen. 
Very short-range photogrammetry can be 
applied to the measurement of the surface 
effects of disease on stone. This application is 
studied in France under the auspices of the 
Historical Monuments Research Centre and 
experiments are done on stones or sculptures 
of various churches. 
Overall surveys of historic centers also are 
on the increase. In various papers we have 
explained the general principle of the use of 
aerial photogrammetry for the making of 
documents which are very useful for the 
study and the management of historic cen- 
ters. These documents include not only 
ground plans but also cross-sections through 
the center and frontal elevations (“géomét- 
raux”) of built-up sectors. Some architects re- 
sponsible for the conservation and develop- 
ment of urban sites have found it useful to 
adopt the normal plan-section-elevation rep- 
resentation used for individual buildings to 
express the volume of an historic center. 
France presents many applications of this 
method. In addition to Thiers and Moulins, 
already discussed, frontal elevations were 
produced by the IGN for Saint Denis, 
Rocamadour, Cahors, Beaugency, Stras- 
bourg, Auxerre, Auch, and also for Athens in 
Greece. In Turkey an excellent survey was 
made of the Ottoman complex of Suleiman 
the Magnificent in Istanbul, known as the 
"Suleimaniyeh" (Prof. G. Tankut and the 
General Directorate of Cartography). In the 
United States the Ohio State University 
School of Architecture (P. Borchers) has car- 
ried out an ambitious program of surveys of 
Indian pueblos in Arizona and New Mexico. 
For this program aerial photogrammetry was 
used to obtain flat projections and plan views, 
but some terrestrial photography also was 
done, and use was even made of some old 
photographs taken before 1900, from which 
plottings were made by hand. 
It is equally interesting to prepare photo- 
grammetrically produced perspective views 
ofthe historic centers, particularly axonomet- 
ric views which are perfectly suited because 
of their conservation of true scale in the three 
coordinate directions. This experiment, con- 
ducted by the IGN for the town of Cahors by 
using aerial photographs and an analog pro- 
cess, was recently applied to the town of Au- 
xerre. 
In this matter automatic processes can be 
very interesting. At the IGN, Y. Egels has 
devised a computer program of calculations 
and automatic drawings which can produce 
any perspective view, partial or complete, of 
a historic center from numerical data stored 
in a data bank. 
Inverse photogrammetry is often applied 
for protecting urban or natural sites in danger 
of being spoilt by new buildings. But graphi- 
cal perspectives are also produced on the 
basis of photogrammetric data. 
More generally, as the documents discuss- 
ed above have accurate geometric proper- 
ties, itis easy to add the drawings of proposed 
new buildings and so to study their integra- 
tion into the historic setting in order to con- 
sider the protection of the latter. Similar 
studies can be undertaken for engineering 
works and all kinds of proposed roads, new 
bridges, etc. Consequently, the specialists 
have excellent documents at their disposal 
for their study. 
BiBLIOGRAPHY 
A complete bibliography on architectural 
photogrammetry has been compiled in the 
reports of the Internationl Committee for Ar- 
chitectural Photogrammetry (CIPA).