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On the Definition of Fundamental Concepts 
in Photogrammetry 
by W. Roos, Oberkochen 
The question of defining some fundamental concepts of photogrammetry has lately 
again become an object of various investigations and discussions [see Literature at the 
end of this article]. One of the causes are the preparations now being made for inter- 
national standardization at the congress to be held at Washington in 1952. For this 
purpose, representatives of several countries met at Paris in December 1950 [7]. The 
results were presented in January 1951 at the meeting of the American Society of Photo- 
grammetry [8]. The aim of these discussions was not to try to lay down final proposals, 
but to create a basis for a later international agreement. The definitions of fundamental 
concepts played a relatively subordinate role, inasmuch as the object of these talks was 
the testing of lenses and cameras. 
The remarks to follow are confined to the definition of fundamental concepts. Even 
this limited theme still offers enough problems, and it will be attempted to treat of 
these somewhat in more detail than was possible within the framework of the general 
transactions. What is here presented are the personal views of the writer. They coincide 
in most but not in all points with the draft of the German Standards Sheet DIN 3035 
(revision of DIN VERM 35) produced within the last two years [9]. As compared with 
the Paris proposals, there are additions and some — by no means unbridgeable — devia- 
tions. These views are not alone the result of the writer’s own work, but are as much the 
fruit of numerous discussions with a considerable number of leading experts in several 
countries. The writer feels obligated to express to all of these, and particularly also to 
his crities, his cordial thanks for valuable suggestions and for the compulsion of having 
had again and again to see things also through the eyes of others. 
By reason of the marked development of instrument construction and instrumento- 
logy, there have been created in the last years a number of new concepts which would 
make it seem necessary to effect an international agreement. It is among the tasks of 
such a standardization to establish the organic connection between these new concepts 
and those already extant, care being taken to conserve the previous definitions as nearly 
as possible unaltered and in the case of the new ones to avoid superfluous rigidity and 
exaggeration. The choice of suitable designations which clearly express the differences 
on the one hand and on the other the logical and factual connections, will be of decisive 
significance for the development of a clear terminology. In individual cases, it is not 
always easy to do justice to all of these demands. The more important would it seem to 
take stock of the fundamental interrelations in order so to win a dependable measure for 
judging each individual case. An attempt to do this shall be made in the following. 
I. FUNDAMENTALS. 
a) Differentiation between mathematical, physical and technical definitions. 
The subject of photogrammetry is to establish the relation between points in the 
object space and points of an image plane. 1) This relation between the object space and 
the image plane may be described in different ways. In particular, three steps or ways 
of representation may be distinguished according to the degree of approximation to 
1) The formation of the image of one plane upon a second plane in rectification is of 
no concern for the definition of the fundamental concepts dealt with in the following, and 
may consequently here be ignored. 
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