The range of possible types of survey (survey of buildings, outside and inside of 
monuments, underground or open cut excavations, vaults, cupolas, statues, small ob- 
jects, etc) is so wide and exposure conditions so different and often so far from 
standards, that it is necessary to contemplate the use of special instruments, mainly 
for reading out, in order to obtain satisfactory results in the most difficult cases too. 
It is however useful to point out that one should put oneself in the best and simplest 
condition in order to carry out normal survey operations; we shall also recognize 
that the traditional instruments are quite enough to solve difficult problems of either 
shooting or reading out: many examples are widely known. 
But there are particular cases requiring either special exposures or special pro- 
cedures of topographic control. 
It is widely known that when exposure conditions are too far from the standard ones 
or control points are not placed in normal position, reading out operations with ana- 
logical instruments are rather difficult, most of the difficulties being due to the limi- 
tations of the instruments themselves. 
Let's remember that for « standard conditions » we mean: 
ist ) in the case of aerial survey, the axis of the camera should be upright and 
consequently «o, « and K of no value; 
2nd) in the case of terrestrial photogrammetry, the axis of the camera should be 
horizontal. 
Everybody has experienced difficult problems, the solution of which has required 
special tricks and taken a longer time. 
Such cases are particularly interesting from the scientific research standpoint inas- 
much as they enable us to make our theoretical knowledge of various subjects deeper 
and clearer. However, from a practical standpoint — and nowadays architectural 
survey does no longer belong to the research field — these problems should be 
regarded to as handicaps which ought to be overcome. 
In our opinion, Analytical Plotters can help solving these problems which are rather 
frequent. As an example let's quote some cases out of our direct experience: their 
solution, if and when possible, required particular care, while could have been easily 
reached using the above instruments: 
a) base of the model was too small to allow reading out to a given scale using stan- 
dard instruments — without Zeiss parallelogram — (shooting basis could not be 
materialized — according to plans — into a pair of stereograms out of a series 
of exposures, cause the position theoretically established for the camera proved 
to be unpractical). 
b) focal length of camera was exceeding the possible focal lenght of plotting instru- 
ment (camera had been suited to close range by increasing its main focal length: 
see « Determinazione di deformazioni con metodi fotogrammetrici in travi in acciaio 
a parete piena » by C. Sena - SIFET Bulletin n. 1 year 1974); 
C) focal length of camera was too small (a possibl solution is to enlarge photo- 
grams: this however is always cause of distorsions in the final plotting); 
d) model appeared on a central strip of photo only; 
e) inclination value w of model was exceeding inclination values obtainable from 
plotting instrument; 
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