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Panel Presentation 
Topic: Lens Distortion Determination 
Moderator: Dr. H. Ziemann (Canada) 
Panelists: Mr. J. Hakkarainen (Finland) 
Mr. G. Bormann (Switzerland) 
Dr. H.-K. Meier (F.R.G.) 
Dr. P.D. Carman (Canada) 
Mr. H. B. Loving (U.S.A.) 
Mr. R. Ondrejka (U.S.A.) 
Mr. C. C. Slama (U.S.A.) 
Mr. J. S. Strahle (U.S.A.) 
Dr. G. Kupfer (F.R.G.) 
Dr. H. Ziemann (Canada) 
Dr. D. C. Merchant (U.S.A.) 
Dr. Ziemann successively introduced his panelists 
who gave short presentations as follows: 
Mr. Hakkarainen: Helsinki University of Technology 
Goniometer for Calibration of 
Wide-Angle Cameras 
He presented the main features of and some 
measurements with the HUT goniometer, which 
is suitable for calibration of several different aerial 
cameras. The instrument can be used for the de- 
termination of the radial distortion, the main 
component of tangential distortion, the lateral 
color error, the optical resolving power and the 
MTF of cameras. One of the two reseau cameras 
was found very symmetrical, but the radial 
distortion of the other was very asymmetrical 
and the tangential distortion great (PPI/19). 
Mr. Bormann: Wild Heerbrugg Horizontal 
Goniometer 
He explained first the measuring possibilities 
and the structure of Wild goniometer, then gave 
a short description ot the measurement of the 
radial distortion and finally presented the cali- 
bration program performed for the reseau camera 
of Wild. 
Carl Zeiss Oberkochen vertical 
Goniometer 
The structure of the instrument was shortly 
described. The visual calibration method is 
preferred because of its simplicity and accuracy. 
Dr. Meier presented some results of an accuracy 
comparison; RMS of the radial distortion mea- 
surements of four different laboratories was 
1-1,5 um. He went on dealing with the problem 
of the reference point in calibration; only the 
principal point of autocollimation (PPA) can be 
realised in the measurement. The point of best 
symmetry (PBS) is, however, the best reference 
point. 
Dr. Meier considered the so called tangential 
distortion as impossible to measure with a visual 
goniometer. 
Dr. Meier: 
National Research Council 
Camera Calibrator 
He described the structure of the NRC instru- 
ment, which has 43 parabolic mirror collimators 
in the same fan. The measurement also with 
infra-red radiation is possible. The collimators 
have no chromatic error. The photographic plates 
Dr. Carman: 
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used in the calibration are flattened with a 
pneumatic flattener with 25 suction caps and with 
interferometric control, which ensures that the 
largest image position errors due to lack of 
emulsion flatness are less than 1 um. 
U.S. Geological Survey Multi- 
collimator 
U.S.G.S. is the Government Agency for calibration 
of aerial cameras. The instrument has four fans 
of collimators. Both photographic glass plates 
and film diapositives made from film exposed in 
the magazine of the camera in the operational 
position on the calibrator are used. The distortion 
figures used in the analytical works of the U.S.G.S. 
are based on the measurements of the diaposi- 
tives made with the last mentioned method (Wil- 
liam P. Tayman: Analytical Multicollimator Cam- 
era Calibration/U.S.G.S.). 
Mr. Loving: 
Mr. Ondrejka: ITEK Portable Artificial Stellar 
Calibration 
ITEKs equipment represents fully new techni- 
ques in the camera calibration. The method is 
based on the use of diffraction patterns produced 
with coherent light generated by a red laser. 
Mr. Ondrejka gave a short presentation of the 
structure of the equipment. For the calibration 
of the whole wide-angle field several photo- 
graphies are needed because of the limited size 
of the coherent light path. 
Mr. Slama: Multi-Plate Multi-Exposure Stel- 
lar Calibration at the National 
Ocean Survey 
The calibration techniques include combined 
data from several two-and-one-half hour chopped 
and presicely timed exposures. Each exposure 
is made with the camera rigidly mounted and 
oriented to a different direction about zenith. 
The double measurement of up to 2400 catalogued 
star images evenly spaced throughout the format 
of each plate provides sufficient redundancy 
to determine accurately the systematic deviations 
of all rays in the format from a central perspec- 
tive. Special provisions have been included in 
the data reduction processes to minimize the 
influence of measurement errors, atmospheric 
refraction anomalies, thermal variations and 
random variations in plate flatness. 
Mr. Strahle: DBA Stellar Calibration 
The parameters of the inner orientation will be 
determined by using simultaneous adjustment 
of multiple stellar photographic plates. The 
photography is carried out with 3 different ex- 
posure times. For computing the SMAC-program 
of DBA has been used. The calibrated focal 
length, the principal point of autocollimation, 
the radial and decentering distortion are deter- 
mined. Finally, Mr. Strahle showed some results 
of Wild and Zeiss reseau cameras. 
Dr. Kupfer: Rheidt Test Field 
The size of this test field is 2x2 sqkm and 
situated near Bonn. The point net is homogenous 
with 41 groups of 3 points. The signals are white 
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