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2. 
DO 
pd 
2. 2. 
Initial Programme. 
The initial programme has been drawn up on the basis of the Statutes of the 
Organization and after having obtained the advice of the national delegates and 
members of the Commission. 
Its aims are: 
a) to establish statistically the accuracies which high precision photogrammetry 
ean ensure, for the triangulations of stereoscopie models, comprised either in 
an isolated strip, or in a group of at least three parallel strips, which reason- 
ably overlap each other laterally and of a length of abt. 10 km. 
b) to experiment with the methods so far accepted for the compensation of errors 
of an aerial triangulation on large scales. 
The limit of the scales to be considered in the field of the so-called large scales 
had not been clearly defined before this question was first discussed by the OEEPE. 
It was not even interpreted according to the uniform criteria in the different 
countries. It has been accepted that this domain extended from a minimum scale: 
1:10,000 to a maximum 1:500. The discussions have shown that the scales of 
1:1,000 and of 1:2,000 are the most important ones in practice. Therefore, the 
tests intended to investigate the average precisions accessible in practice and the 
best working conditions were centered on these scales. 
With regard to the precision an attempt has first been made to find a way of 
expression which should as much as possible he independent of all individual 
interpretation. 
In view of the fact that the indication of the differences between known and 
observed coordinates serves as base for all considerations of precision and that 
these data allow everybody to interpret the results, the Commision has decided to 
use the coordinate in space of all points which are observed in the instruments, 
for the study of errors. 
On the other hand the measurements carried out on the plates and expressed in 
microns are susceptible of being translated into scale of map or of machine. They 
allow comparisons in the same way as the absolute coordinates. Consequently it 
has been determined that 'the precisions which might result from the procedures 
shall be determined by the average square error expressed in microns in the plane 
of the negative and also in coordinates". 
As regards the precision it would be well to consider the importance of the con- 
ditions of the photography. There are two ways of setting the problem: 
a) to determine a scale of photography to be adopted in order to reach a certain 
precision by basing oneself on practice, 
b) to use photographs executed on different scales and to check the resulting 
precisions. This second method permits making quick use of existing material; 
such was the case with the flights executed in Austria. 
It has been decided to make up series of photographs on three different scales, 
viz 1 : 5,000, 1 : 10,000, 1 : 15,000 in order to determine the precision which can 
be obtained at each photographic scale adopted. 
The examination of the photographs may also contribute to the study of the rela- 
tion which exists between the different photographic scales and the identification 
of the details in the terrain. 
For a fixed photographic scale it will be possible — beginning with tests of Com- 
mission B — to establish statistically the loss of precision which occurs according 
to the number of the triangulated pairs, taking into account the sensitive material 
used (plates, films) the characteristies of the terrain (plain, hill, mountain) the 
angle of field of the cameras used and the number and quality of the control 
points, determined on the terrain.