Results of Practical Investigations into the Accuracy 
of Aerial and Terrestrial Photographs 
Tests of the fundamental operation number one of photogrammetry 
Communication to the IX International Congress of Photogrammetry 
Commission I 
By B. Hallert 
Introduction 
As indicated in [1] the photogrammetric procedure can be divided 
into a series of fundamental operations, the errors of which constitute 
the errors of the final results of the photogrammetric procedure. The 
theoretical laws for the error propagation from the fundamental opera- 
tions to the final results are well known and have been applied for a de- 
termination of the accuracy which is to be expected in the final results of 
the photogrammetric procedure, see for instance [2]. In such investiga- 
tions it is of the greatest importance to distinguish between regular 
(systematic) and irregular (accidental) errors of the fundamental ope- 
rations. In general, it is required from any measuring method that 
regular errors of the fundamental operations are determined as well as 
possible and that the residual irregular errors, which cannot individually 
be corrected are estimated in a reliable statistical way. 
Jelow the results of some investigations of the fundamental opera- 
tion number one, the photography, will be demonstrated. 
First some attention will be paid to the influence upon the image 
coordinates from lacking flatness of the image surface. This is of parti- 
cular importance for photogr: immetry concerning the camera (the focal 
plane frame, the Tor re b: ick, glass plates) as well as the plotting in- 
struments (the supporting frame of the projectors, glass diapositives). 
The geometrical quality of the photographs will be tested with the 
grid method according to reference [3]. Particular attention will be 
paid to the systematic disturbances of the photographs, primarily the 
radial distortion, and the standard error of unit weight of the image 
coordinate measurements. This latter factor is of basic importance for 
photogrammetry in general. 
I. The influence of lacking flatness of the image plane upon the 
image coordinates 
Evidently the flatness of the image plane plays a most important role 
for the accuracy of the image coordinates. It is simply not possible to 
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