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posal), contrast rendition, and tangential distortion. All these terms are simply
omitted in the proposal.
Some of these omissions will probably be acceptable to American photo-
grammetrists if they recognize the fact that the determination of the equivalent
focal length and of the “American” principal point is not necessarily of uni
versal technical importance and interest.
Some omissions can probably be easily rectified by permitting the use of
the alternate term (contrast rendition, for example).
Some omissions, however, will require more profound discussion of the
supporting argumentation. Thus the argumentation for restricting the term
“distortion” to its theoretical content should be critically evaluated, because
it is contrary to the prevailing American and European practice. If such a
rather artificial argumentation is accepted, then, for example, a new term
should be invented also for the measured spherical aberration, because imper
fections of manufacture may destroy its perfect symmetry about the optical
axis.
Terminology frequently proves to be a serious stumbling block in stand
ardization undertakings. Let us hope that problems of terminonlogy will be
easily resolved by Commission I, and that its proposal will be evaluated with
the spirit of compromise and international goodwill, which are the basic con
ditions for the success of our undertaking.
Mr. F. L. Corten:
Mr. Chairman, ladies and gentlemen. At the International Congress of
Photogrammetry in 1948, Captain Reading stated that we were badly in need
of international standardization of calibrating and measuring the performance
of photogrammetric cameras. The result of his initiative and of the work done
by many of those present is now lying before us.
I shall confine my remarks on these proposals to a few points.
With section 1, dealing with the measurement of resolution and photo
graphic performance, I can agree for the time being.
Section 2 deals with the calibration which should preferably be done
photographically, whereas a visual goniometer is also permissible. The philo
sophy underlying the photographic method is a very sound one and it is gene
rally agreed that in principle the photographic method is to be preferred. One
point remains to be established in the near future: what accuracy can be
reached, in other words; what is the statistical and chronological spread in the
results of the photographic method, if a larger number of identical calibrations
is carried out? In view of the recent developments in optics and in mechanics,
both in cameras and in plotting apparatus, we should be able to arrive at a
reliability of ± 1 micron, that is less than one ten thousandth of an inch! This
is a very rigid demand, but it is clear that the claims to be set for the calibra
tion should be at least as exacting as the claims set for modern precision survey
cameras. It is true that Item 2.14.10 requires a statement of the accuracies of
all information provided, but what the photographic method is capable of in
this respect has not yet been investigated systematically. Therefore, it would
be a valuable contribution if such an investigation could be made as a coping
stone for the calibration of survey cameras. There is an additional remark on
section 2 in general: The establishment of a complete set of fundamental pho-