carried out by spirit level or tacheometer. In both cases we have a 
certain uniformity between measurements made by tacheometric 
methods and tests made by the same methods as there is still. 
The test of a traverse, for instance, may be made by means of 
another tacheometric traverse based on trigonometric points belonging 
to the same net, making sure to not include in the test some errors due 
to the gaps of the basic net or to the differences of adjusting. That did 
no longer happen when, using the surveyor methods of aerial survey, 
the tester went on to use tacheometric methods. Suddenly we had to 
notice that many of the rules of verification were not fit for the new 
method. We made a gradual revision and a gradual adaptation of 
testing methodology. 
Nevertheless, some residual reminiscences, not always correctly 
retained, of the methodologies created for quite different methods, 
remain in the methods used to test works made by means of photogram- 
metry. 
1. 3. Criticism of testing methods. 
The international experimental researches directed by the « Com- 
mission C » of the European Organization for photogrammetric studies, 
certainly can improve and make uniform the testing methodology. Till 
now, each surveyor followed a personal method, criticised the one of 
the others, and unwillingly accepted that of his own customer. 
The possibility of testing the good execution of one step of work 
from the results of a following step is a peculiarity of the photogram- 
metry. It is possible, for example, to orientate a pair of photograms in 
respect to the sistem of axes of the cartographic projection, when we 
know the planimetric and altimetric co-ordinates of two points and also 
only the altimetric one of a third point not set on the same line with 
the other. Normally, in large scale works, the photograms are orientated 
by using five points: four marginal and one central. When the 
orientation has taken place, the possibility or not of according the 
machine co-ordinates with the terrestrial co-ordinates of all the known 
points gives an idea not only of the precision attained in the inner and 
outer orientation, but also of the good execution of the field works and 
of the calculation for determinating the coordinates of the points 
themselves. Then it would not seem necessary to test on the fields, by 
classic methods, the accuracy of the preparation of the control points. 
Except for some errors of identification, the error of a plotted point is 
caused by residual errors of orientation. 
    
      
   
  
  
  
  
  
  
  
  
  
    
   
   
  
  
  
  
  
  
  
  
  
  
    
   
  
  
  
  
  
    
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