25
Zeiss SMK 40,120, TMK. Topogon 60 mm
Radial Distortion (averages of 10 lenses )
dr'jjm
Standard Errors of Unit Weight of Image
Còordinates (RMSV).
s^m
Fig. 3.12: 16. Results of partial calibrations of photographs from
Zeiss SMK and TMK cameras with Topogon lenses f: 11, c =
60 mm. (1 SMK 120, 2 SMK 40, 4 TMK.) Cameras from the
Divisions of Photogrammetry at the Institutes of Technology in
Stockholm and Helsinki.
Summary
The partial calibrations of photographs from different
imaging devices in terrestrial photogrammetry can be
summarized as follows.
1. It is most important to partially calibrate photo
graphs from every camera or other imaging device to be
used for measuring purposes. Unexpected weaknesses have
proved to be present also in photographs from cameras,
calibrated with usual methods in the manufacturer’s
laboratory.
2. The most common geometrical disturbances in pho
tographs are
a. lacking flatness of the negative material and
b. radial distortion effects, which can be caused by the
lens or by lack of flatness of the negative.
3. A pronounced weight variation in the image coor
dinates has in general been found in terrestrial photographs,
probably mainly caused by lacking flatness of the negative.
4. Cameras, equipped with glass plates in the negative
plane against which the glass plate or film negatives are
mechanically pressed at the moment of exposure have
proved to give significantly better geometrical quality
than comparable cameras without such devices.
5. Therefore it would be most desirable that all ter
restrial cameras for measuring purposes be equipped with
such glass plates, in which, also, fiducial marks can be
engraved. Also, there is reason to use film negatives, pref
erably on polyester base, instead of glass plates only, in
particular for the use of colour and infrared film.
3.2 Complete Calibrations of Photographs
The photography must be made under such conditions
that all elements of the interior orientation can be com
puted, including possible systematic disturbances, and the
basic standard error of unit weight of the image coordinates.
For aerial cameras and other cameras which are focused at
infinity, there are laboratory and field devices available,
well known from literature. In the report Ref. 3: 2 some
results of laboratory calibrations of pictures from aerial
cameras have been described. The method of least squares
has been used for the statistical determination of the
elements of the interior orientation, the basic accuracy of
the image coordinates and the accuracy of the elements.
Through statistical tests it is then possible to judge the
significance of the corrections to the preliminary values of
the elements before the calibration as well as of possible
differences between the obtained elements and the cor
responding previously determined data.
Through the courtesy of the U.S. Geological Survey and
the Wild-Heerbrugg Co. some more experiments have been
performed with photographs from aerial cameras, taken in
the multicollimators of these organizations.
Results of these experiments will next be briefly presented
and discussed.
3.21 Complete Laboratory Calibrations of Photo
graphs from Aerial Cameras
In the report Ref. 3:2 a rather comprehensive analysis
was made of the results of complete calibrations of photo
graphs from the U.S. G.S. Multicollimator. In particular
the standard errors of unit weight of image coordinates
were found as follows:
For glass plate negatives: 2.8 /;m
For diapositives, contact prints: 3.2 /./m
For diapositives, projection prints: 4.8 ¡um
It is evident that the printing of the negative causes some
decrease of the accuracy. In particular, the projection
printing causes significant decrease in the geometrical
quality, probably because of the inevitable lack of flatness
of the diapositives, and possibly also because of the thick
ness of the emulsion. The weight variation with the radius
was also most pronounced in the projection diapositive
prints, see Fig. 1.61: 5 in Ref. 3: 2.
