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SUB-COMMISSION IV-4 
FUNDAMENTAL QUESTIONS IN RELATION TO 
CONTROLLED EXPERIMENTS 
President: Prof B. Hallert Associates: Mr L. O. Hosen; Mr C. O. Ternryd 
Presentation of the General Report of Sub-Commission IV-4 
in the Meeting held on Friday, 9th September, 1960 
by the President, Prof B. Hallert 
In a few words I shall introduce the work 
and results of sub-Commission IV-4 during the 
period 1956—1960. Since all details can be ob- 
tained from the printed report I will make a 
very brief summary here, and mainly to avoid 
misunderstandings will especially point out 
some limitations of the methods and procedures 
which have been applied in our sub-Commis- 
sion. 
We have concentrated upon the investigations 
of the fundamental operations of photogram- 
metry, and I have tried to determine some im- 
portant regular errors and to estimate the 
magnitude of the residual irregular errors of the 
central projection of photographs. This is en- 
tirely in accordance with the usual procedure 
in, for instance, geodesy. In particular, the in- 
struments and models have been tested by our 
Commission since we have not heard of a possi- 
bility for testing the photographs themselves. 
We have investigated the propagation of the 
irregular errors through the entire photogram- 
metric procedure, and have estimated errors of 
the final results expressed as mean values of the 
standard errors of the co-ordinates in planimetry 
and elevation. This data we have estimated 
could then be directly checked by a comparison 
with the mean square values of the discrepancy 
between the photogrammetric and the geodetic 
co-ordinates according to sub-Commissions 
IV-1 to IV-3. 
Since no exact agreement can be expected in 
such a case, the significance of the differences 
between theoretical and practical values have 
been judged with the aid of statistical tests, in 
particular confidence limits according to well- 
known principles and according to a certain 
confidence level which is chosen as 595. In all 
cases, an astonishingly good agreement has been 
found between theoretical and practical results, 
and it seems important that some theoretical 
relations of significance for photogrammetric 
practice have been applied. 
It seems possible to construct certain speci- 
fications for photogrammetric work concerning 
Archives 5 
the fundamental operations, in particular from 
the x and y parallaxes in oriented models, but 
it must be emphasised that the fundamental 
operations (1) and (2) — the plotting of the 
photographs in the plotting instruments, in other 
Words — have to be especially checked first. 
There have been some very regrettable mis- 
understandings in this respect since the Stock- 
holm Congress when these principles were 
published, in spite of the clear reservations 
which were made there. I will here repeat my 
own words in the paper on the grid method and 
Y-parallax method for the determination of 
systematic disturbances in aerial and terrestrial 
photographs, which was published at the Stock- 
holm Congress in 1956. I quote again: 
"Finally, it has to be emphasised that the 
grid method gives more accurate and correct 
information on systematic disturbances than 
the y-parallax method. The latter method is 
particularly limited by the considerable cor- 
relation between the two pictures. There may 
be distortion effects in the two pictures which 
cannot be distinguished in this way. Neither 
of the two methods can give the absolute 
determination of the orientation under as- 
sumed conditions." 
The expression "correlation" may perhaps 
need some extra work. Since a parallax is al- 
ways defined as a difference between two image 
co-ordinates which may be enlarged, it is quite 
evident that any source of error which has a 
similar effect or an equal effect upon the two 
co-ordinates will not show up as a parallax. This 
means, for instance, that the influence of the 
earth's curvature, symmetrical refraction, some 
kind of film supporting glass plates in the 
camera — as in the English cameras, for instance 
— certain curvature of the locating bag or nega- 
tive glass plates, certain shrinkage of the nega- 
tive material, in particular a fine shrinkage, 
cannot be determined from parallax methods. 
The image co-ordinates in such a case become 
correlated and they also become correlated via 
the element of their relative orientation, in