eR. M UD —n 
mI. 
ILI 
Mw 
— M I 
ww 
w UJ) LU I 
  
f) convergency value ¢ of model was too high; 
g) high value of A Z (too much difference of level among camera stations); 
h) high value of AY + A w (camera stations with rather different exposure dis- 
tance as to the monument datum plane); 
i) certain parts of model being out of depth of field of Z of instrument, it was un- 
practical to read them out to a given scale. 
The widespread use of modern lifting devices originates a range of problems that 
are the result of combinations of the above mentioned cases. While those devices 
are essential to carry out certain types of exposures, on the other hand they create 
a number of problems owing to the fact that te lift holder has to follow the shape 
of the ground on which it moves (such as excavations or uneven ground): right posi- 
tioning of camera (or bicamera), according to exposure project, is therefore rather 
difficult. Of course, one can resort to various tricks; namely: basket can automati- 
cally take an upright position; heigth from plane of site can be measured; camera 
can be placed in appropriate positions; camera can be taken back on basket, along 
the vertical, on the plane of site; however, it is always difficult to keep constant 
exposure alignment due to possible imperceptible movements mainly of the basket, 
when highly positioned (up to 20-25 mt). 
No doubt Analytical Plotters have been implemented for aerial photogrammetry, i.e. 
for map-making and other special applications. 
Their use in Architectural photogrammetry is somehow peculiar, mostly if the solu- 
tion of one of the above cases is required (plotting of models with great inclination, 
great convergency, etc.). 
However, to extend the use of Analytical Plotters in the above direction is only a 
matter of soft-ware, and, as far as we know, all such instruments can help solving 
the above problems inasmuch as the relevant processing programs contemplate — or 
may contemplate — exposure conditions far from the standard ones. 
During the International Symposium of Architectural Photogrammetry held in Athens 
we have already brought out an example of performance of the Digital Stereocarto- 
graph (D.S. - Officine Galileo), namely the reading out of a set of models concerning 
the survey of the Roman Amphitheater in Susa; the problem with such models was 
that they appeared on the central strip of photos only. 
Plotting them out through analogical instruments proved unpractical, for it was 
rather difficult to find suitable points even for relative orientation. 
Galileo Digital Stereocartograph has then been experienced in the plotting of models 
derived from exposures taken with a great inclination angle and from converging 
shots. 
These performances, relevant to surveys of archaeological excavations in eastern 
Sicily, are referred to in another publication. (See: DeMichelis - Sena - Un'applica- 
zione del D.S. nella restituzione di coppie stereoscopiche particolari nel rilievo di 
zone archeologiche).