TECHNICAL PROGRESS IN ARCHITECTURAL PHOTOGRAMMETRY 1515 
In order to be able to rectify photographs 
obtained under such conditions (e.g., camera 
inclinations of 30? and 60? or 30 and 70 
grades), special devices must be constructed 
for a particular inclination angle and a par- 
ticular focal length. Only Carl Zeiss actually 
markets such a device (KEG-30). 
ADAPTATION OF PLOTTING INSTRUMENTS TO A 
WIDE RANGE OF PRINCIPAL DISTANCES 
The wide range of principal distances and 
the resulting need to adapt the plotting in- 
struments are not problems peculiar to ter- 
restrial photogrammetry. Modern plotters 
generally have greater versatility regarding 
focal lengths (from 85 to 310 mm). However, 
in architectural photogrammetry, the wide- 
spread use of small metric cameras necessi- 
tates a further extension of plotting 
capabilities towards shorter focal lengths i.e., 
in the 50 or 60 mm range. Three solutions 
have been devised: 
e the construction of special equipment 
solely for photography taken in the normal 
case (this solution is not recent); 
9 the selection of a fairly wide range of 
focal lengths but tending towards the shorter 
ones, e.g., Zeiss Jena Technocart (focal 
lengths from 50 to 215 mm); or 
e the manufacture of additional devices 
for the plotting of small camera photo- 
graphs, e.g., Carl Zeiss devices for the 
Planimat D.2. 
DEPTH OF FIELD OF A SUBJECT: Z-RANGE OF 
PLOTTING INSTRUMENTS 
With respect to the depth of field of a sub- 
ject, the simplified instruments constructed 
for short principal distances and the normal 
case have generally good properties; but, un- 
fortunately, the capabilities of the new, more 
or less universal, instruments are smaller. 
They are generally limited to a z-range on the 
order of 300 mm; this range is usually suffi- 
cient but may not be so always, and in any 
case it usually imposes restrictions on the 
scale of the model formed in the instrument. 
The use and development of analytic plotters 
should lead to real progress in this domain 
and in the domain of steep slopes. 
METHODS 
Plotting and rectification are the two prin- 
cipal methods employed in architectural 
photogrammetry, but other photogrammetric 
methods are now used for the survey of 
monuments and sites. 
New experiments in the field of or- 
thophotography have demonstrated its ac- 
ceptability for architectural surveys, pro- 
vided that the subject does not present sud- 
den breaks in continuity. Based on.the work 
of the Officine Galileo (W. Ferri) on the in- 
side of the dome of Santa Maria del Fiore in 
Florence, good orthophotographic surveys 
have been done in Poland, by J. Jachimski 
and Z. Sitek (ruins of a medieval castle, the 
walls of which are both complex and irregular 
in fabric), and in Western Germany, by M. 
Dóhler (Roman wall) and E. Seeger (Baroque 
decorative features in stucco). The surveys so 
obtained were used in combination with plot- 
ted line-drawings of the parts of the monu- 
ment which presented too high a relief. 
We should remark on the increase in the 
number of cases where aerotriangulation was 
used. C. Sena, in Italy, and H. Mohl and E. 
Mohr, in Western Germany, have performed 
experiments in the adaptation of this 
technique to suit architectural surveying, and 
have produced encouraging results; this 
should simplify the task of measuring control 
points. 
We know that analogical numerical 
stereophotogrammetry can offer a greater de- 
gree of accuracy than graphical plotting 
where it is required to measure certain im- 
portant features of a building such as lengths, 
distances between characteristic points, dif- 
ferences in height, etc. 
The advantage is considerable if one de- 
sires to determine the precise geometrical 
characteristics of buildings dating from 
periods of extreme refinement in architec- 
ture, such as Archaic and Classical Greece, 
and the Baroque. Thus itis normal to find the 
method used in Sicily in the work being done 
there by the Turin Polytechnic Institute and 
the German Archaeological Institute at 
Rome, and for the surveys of the Acropolis 
buildings at Athens made by the French In- 
stitut Géographique National (IGN). How- 
ever, numerical stereophotogrammetry also 
is extremely useful for surveys in which the 
reference planes are not parallel to the Carte- 
sian axes of the plotting machine. Here a 
numerical survey involving a very large 
number of points, followed by calculations 
and by drawing on an automatic tracing table, 
can offer an excellent solution. The IGN has 
used this method for the surveying of arches 
of vaults, for example, and for facades which 
(as in the case of some ofthe upper portions of 
the Farnese Palace) could be photographed 
only very obliquely. 
An excellent example of this process is of- 
fered by the photogrammetric survey of the 
Jameh Mosque at Isfahan made by the Rassad 
Topographical Company for the Historical 
Monuments Conservation Department of 
Iran. It was possible to photograph certain of