Full text: Commissions III and IV (Part 5)

  
  
  
  
198 PRESENTATION OF THE GENERAL REPORT OF SUB COMM IV-4 
particular the phi element. This limitation had to 
be emphasised and never forgotten when apply- 
ing methods where we measure differences or 
parallaxes. We should not regard the parallax 
method as a major means which solves all 
problems, but we should take it for what it is: a 
convenient and inexpensive aid for checking the 
fundamental óperation (3) of photogrammetry, 
the relative orientation. 
Under normal circumstances, in particular 
with respect to the first two operations, we can 
get very valuable information about some 
systematic or regular error of the combined 
operation (1) and (2), and primarily about the 
irregular errors. The control experiments have 
to give important qualities satisfactorily. We can 
doubtless find certain specifications upon such 
measurements, but of course we shall always be 
grateful for checks from extra control points in 
the models. 
Evidently, no detailed analysis of the individ- 
ual co-ordinate errors can be performed from 
such measurements. It is more in the statistical 
sense that we use such measurements here. 
Finally, I should like to emphasise that the 
work and results of Sub-Commission IV-4 are 
nothing but a check of the method of least 
squares, law of error propagation and the cen- 
tral limit theorem from statistics. It may also be 
mentioned in this connection that the principles 
which have been applied to the work of Sub- 
Commission IV-4 are by no means a recent in- 
vention. The first test, according to this method, 
was made in 1937—1938 in connection with the 
introduction of the Multiplex instrument to 
Sweden. In April 1938 a proposal for tests of 
this type was written up and forwarded to the 
Geographical Survey Office of Sweden. In 1944 
the basic principles were published. 
After these introductory remarks Prof Hallert 
showed a number of slides representing the 
following tables and diagrams of his report: 
1. Table 1, p 6 gives some information about 
the accuracy obtained with Wild Autograph A7 
and Zeiss Aereoplanigraph C8. 
2. Table 1 of the "additional remarks" to the 
General Report IV-4 shows a detailed compa- 
rison between the theoretical determination of 
the accuracy from y-parallaxes which we have 
here, and the corresponding determination from 
errors on the ground between geodetic and 
photogrammetric co-ordinates. He stresses the 
agreement between both values. 
3. Table 2 of the same document gives the 
same comparison for the results of the Renfrew 
test of Commission IV-3. 
4 and 5. Histograms p 14 of the General 
Report IV-4. 
6. Fig 7a and 7b p 18 of the General Report 
IV-4. This summary of the distortion deter- 
mined by Hallert from observations of a number 
of participants proves that the standard error of 
the average is in accordance with what we can 
expect theoretically. 
Then Mr Hallert continues as follows: 
Anyhow, I think we can state that these ex- 
periments have given us astonishingly good 
results which may be of use for future develop- 
ments in photogrammetry. 
Dr H. HArry: Thank you very much. Yo 
will have an opportunity to discuss this com- 
munication on Monday at 15.40 in room 381. 
  
E o es
	        
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