(209) 
a capital “M”. The cadastral problem, the problem of the general map of terrain 
rich in detail of all sorts, or that of the smaller scale map of underdeveloped 
areas do not require the same equipment at all. So why try to compare them 
by a common control method? 
I assure you that these various objections are not meant to nullify the very 
real and desirable effort which is being made towards international cooperation. 
They are intended only to explain the difficulties and to define our purpose 
better in order to hasten its achievement. It appears necessary for the stand 
ardization of world-wide tests to be based on finished equipment, under con 
ditions of use, without stopping half way and without trying to compare 
pieces of equipment which are really not comparable because they are intended 
for use in solving different problems. 
The result is that a project such as that in which we are interested should 
not pay too much attention to details and should be concerned with: 
1) the precise definitions which are as desirable in this field of photogram- 
metry as they are in many others; 
2) the definition of the way in which results are to be given; 
3) the standardization of types of targets for resolving power and distortion; 
4) recommendations as to the description of control methods which can be 
used effectively, the indication of the degree of precision achieved by the 
methods used, the publication of the numerical characteristics of pieces of 
equipment of the same type, etc. 
It is not necessary to do more. It is up to the user to judge the number of 
tests which should be undertaken or the information to be requested from his 
supplier, in relation to the problem in hand. A person who has in mind no 
more than photographic coverage or the setting up of photoplans will require 
much less than the person who wants to use his apparatus for aerotriangulation. 
The latter will certainly not be content with a distortion measured along two 
diagonals. 
Briefly, it is unnecessary to try to do more than to agree on the definitions 
and to prescribe measures which will facilitate the interpretation of the per 
formance claimed. 
It is probable that a project similar to that proposed will be put to the test 
by various Institutes in the years to come. I propose that the present project 
be modified in order to take into account at least some of the general ideas 
which I have just outlined; the modifications which might be applied are as 
follows: 
— not to speak of the control of the lens alone 
— to test the resolving power both on high contrast targets and on tar 
gets of low contrast, taking into account the effect of stray light, not 
to measure the stray light itself; 
— to make tests with any filter for the correction of vignetting or any 
other filter used in practice (elimination of atmospheric “haze”); 
— not to speak of the “image displacement” and to retain the idea of 
distortion for actual lenses; to define the distortion in relation to the 
meridian plane and the angle of field; to define the average distortion 
of a series of cameras of the same model, rather than the theoretical 
distortion of the ideal camera;