Eleventh Congress of the 
International Society for Photogrammetry 
Lausanne, Switzerland 
July 8 to 20, 1968 
Commission III Invited Paper 
The Acquisition of Data 
in Aerotriangulation 
G. de Masson d’Autume 
Institut Géographique National 
Paris, France 
Introduction* 
n all aerotriangulation procedures there 
are two distinct and more or less indepen 
dent phases. The first phase comprises a 
number of operations such as the taking of the 
photographs, the selecting of the aerotriangu 
lation points, their marking, the formation of 
the models and the measurement of their 
spatial coordinates in the case of instrumental 
methods, or the measurement of the photo 
graphic coordinates in the case of analytical 
methods, etc. The numerical data thus ob 
tained are then treated in a mathematical 
procedure, which is the second phase. 
During the meeting of Commission III at 
Bad Godesberg, it was decided that each of 
these phases would constitute a field of inter 
est and would be a basis for a report to be 
presented at the Congress at Lausanne. This 
decision was not made without lively dis 
cussion and the agreement was not reached 
without a compromise: first, the subject of 
auxiliary instruments would continue to be 
treated separately; further, a new field of 
interest would be created to permit discussion 
and comparison of different methods on the 
whole. But, in so doing, we evidently also 
risked a certain amount of overlapping, pos 
sibly accompanied by some disagreement in 
the conclusions reached. 
The present report treats, then, the ac 
quisition of data; but it will not be possible to 
make it exhaustive because the subject is too 
broad: hence, we will limit ourselves to points 
that are important, new, or controversial 
concerning the taking of the photographs, the 
instrumental procedures, and the problem of 
transferring control points. 
The Taking of the Photographs 
The taking of the photographs constitutes 
an essential element in all aerotriangulation 
projects. Too often, it is done according to the 
demands of the compilation, whereas, with a 
minimum of additional expense, it could be 
done in such a way as to reduce considerably 
the amount of field work, increase the preci 
sion, and simplify the calculations (required 
for aerotriangulation). 
In general, cameras mounted for vertical 
exposures are used. Despite their theoretical 
advantages, multiple cameras have never had 
much success, doubtless because of the com 
plications in their use, and seem to be de 
finitely abandoned. The nonclassical con 
tinuous-strip and panoramic cameras have 
still less chance of being used again in present 
practice. One has, then, little choice but to 
use conventional cameras, wide-angle and 
super-wide-angle. The use of the latter, at as 
high an altitude as possible, is the most 
economical solution, because this reduces the 
number of exposures needed to cover a given 
area; it also gives the best altimetric accuracy, 
especially if the density of the control net 
work is weak. On the other hand, if one de 
sires to have the highest planimetric preci 
sion, wide-angle and normal-angle cameras 
are undoubtedly preferable. 
The advantages of plates over films, and 
the advantages of reseau cameras, have never 
been incontestably proven. All that one can 
say for certain is that lack of flatness and 
dimensional stability in the sensitized sur 
faces are among the factors that limit the 
precision of aerotriangulation, and that they 
reduce to an illusion any effort to measure the 
* This English version was translated from the French original text by Mr. Robert C. Eller and 
Mr. Morris M. Thompson of the U.S. Geological Survey. The paper will be published in French in the 
Bulletin de la Société Française de Photogrammétrie