20 
Summary. 
The results of the partial calibrations of aerial photo 
graphs under operational conditions have shown: 
1. There have been found considerable differences be 
tween the radial distortion of the photographs and of the 
lens according to laboratory calibration. 
2. It is therefore of obvious importance to calibrate, at 
least partially, aerial photographs under operational con 
ditions in order to be able to apply corrections in connec 
tion with the reconstruction of the bundles of rays. The 
corrections may be different for analogue and analytical 
work, depending upon the nature of the systematic errors. 
3. There exists in practically all tested aerial photographs 
a considerable weight variation between different parts of 
the photographs. The weights can be expressed at least 
approximately as functions of the radii from the principal 
point. This is of importance, primarily for analytical resti 
tution. 
4. Considerable improvement of the basic accuracy has 
been found in photographs on polyester base in compari 
son with acetate base. The root mean square values of the 
standard errors of unit weight have been found in the 
relation approximately 5 : 8. This is equivalent to a linear 
difference of approximately 7 micrometers. The conse 
quences of this fact particularly for the selection of plott 
ing instruments and methods are evident. 
5. It is possible to correct certain systematic errors of 
the image coordinates from the discrepancies in fiducial 
marks. It would be of value to use at least 8 fiducial marks, 
the accuracy of which must be high. Still more valuable 
would be at least one more given point if it can be located 
in the neighbourhood of the principal point. 
6. One reseau camera has been used for partial calibra 
tion described here. No significant improvement of the 
accuracy of the final image coordinates has been found. 
More similar tests of such cameras of different makes are 
desirable. 
7. The comparison between the standard errors of unit 
weight of image coordinates and the standard errors of 
unit weight of corresponding y-parallaxes showed a con 
siderable correlation effect, the correlation coefficient 
amounting to about 0.60, and the rectangular weight 
coefficient to about 0.70. Taking this fact into account it 
should be possible to estimate the basic accuracy of image 
coordinates from the determination of the standard error 
of unit weight of y-parallaxes which can be done in any 
arbitrary pair of overlapping photographs. The standard 
error of unit weight of image coordinates has been found 
to be about 1.4 times the standard error of unit weight of 
the j-parallaxes. The errors of the measuring instrument 
(stereocomparator Wild StK 824) can be neglected in this 
case. 
8. It is highly desirable that the geometrical quality of 
aerial photographs be checked at suitable intervals and 
under operational conditions. Tolerances can be established 
according to ordinary principles. 
3.12 Results of Partial Calibrations of Terrestrial 
Photographs 
With the test fields, briefly described above, and mea 
surements of image coordinates in the stereocomparator 
Wild StK 824 a great number of partial calibrations of 
photographs from various cameras such as phototheod 
olites, stereocameras, ordinary amateur cameras, X-ray 
instruments etc. have been performed. Because of the limited 
space here, only a few examples of all results will be shown. 
See Figs. 3.12: 1—16. In the summary some general points 
of view, gained from the experiences had in this work, 
will be extracted. In particular, cameras tested for use 
in medical applications of photogrammetry have given 
interesting results proving the necessity of careful in 
vestigations of such cameras for purposes where the 
quality of the results can be of particular importance.