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of Mr. Schwidefsky to cite a trial of electronic computing applied to aerial 
triangulation executed in Great Britain. For this trial made on 40 stereoscopic 
models measured in the stereocomparator, the time of calculation averaged 45 
seconds per model. 
At 5.21 M. Cruset (France) intervened in the discussion. “The only test”, 
said he, “which makes sense, is a complete solution of a given cartographic 
problem, from the taking of the photographs to the making of the map. All 
the world knows that Zatopek has won three races in the Olympic Games but 
no one knows his measurements. That is to say, that it will be interesting to 
make complete tests not only on the plotting instruments themselves, but also 
on the speed of production, the cost in time and money. To cite another 
example, competition has been the source of the progress realized in automobile 
construction. Only competition is truly the generator of progress”. 
At 5.24 Captain Reading (U.S.A.) President of the International Society of 
Photogrammetry, took the floor in his turn on the subject of the Pennington 
Standard Tests. 
«All photogrammetrists are greatly indebted both to Mr. Pennington and 
to Mr. Schermerhorn for the thoughts they have expressed here. Each user or 
purchaser of a stereoscopic plotting machine ought to seriously consider and 
make sure he perfectly understands their remarks. 
According to my experience, each criticism, each remark made by Pro- 
fessor Schermerhorn is correct and valuable. However, if he fears that one may 
be misled by too simple ideas about the tests proposed by Mr. Pennington, I 
fear, in turn after his remarks, that one may think that the tests are not neces- 
sary. But if one listened closely I am sure that this was not what he wished to 
say. He himself requested a set of test plates for his laboratory at the end of 
his remarks. 
I regret that we do not have the plates ready for him. Several months ago 
we requested Mr. Wheeler, first assistant to Mr. Mann, manufacturer of com- 
parators, to make us a set of plates by working at night to use a finished com- 
parator before it was shipped, as we did not have money enough to pay for 
regular work. He had many difficulties but finally obtained targets resolving 
114 lines per millimeter just a week before the Congress. We have made stere- 
oscopic pairs, but to all appearances we have obtained copies precise only to 5 
or 4 microns instead of the 1 micron as Mr. Pennington requested. The posi- 
tions of the targets seem also to be out of perpendicular by 20 microns or more. 
We have thought of several means of improving these first results, but shall 
have to wait for another order of plates to continue our efforts. We have learn- 
ed in the course of these trials several things which should be of much value 
for improving the precision of photogrammetry. 
There is great value in standardized tests. If we discuss and publish such a 
test fully and freely, all photogrammetrists will listen and understand the 
advantages and utilize the tests. If not, many will undoubtedly leave the test 
plates in their boxes, thinking chat such tests are the business of the manufac- 
turers and the mechanics who erect the machines. 
Another great advantage of such tests and of an open discussion of their 
limits of precision, is that, each time a more precise test is found and made 
known, the manufacturers find means of perfecting their products so as to 
obtain the higher tolerances the tests show to be necessary.