error
accu-
annot
se in.
ps of
nor-
n had
igure
-ound
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nd 16
Radial distortion according to the grid
me thod
manu facturer
Fig. 2. Radial distortion of the Stereoplanigraph for base in 120 mm (above) and
base out 120 mm, at a projection distance of 200 mm. c — 100 mm. The right
projector.
The fact that the same kind of lenses are used in the camera as well
as in the projectors does not guarantee that the radial distortion will be
compensated. It is well-known that different specimens of the same
kind of lenses show quite different distortion curves. Not even if the
camera and the projector lenses show similar distortion amounts, therc
IS à guarantee of freedom from distortion effects. Investigations [4]
have shown that to all appearances there 1s some difference between the
distortion, determined in the laboratory, and the one obtained in aerial
pictures. The curve used as comparison in the figures is based on labo-
ratory determinations. Besides the radial distortion the lenses can be
afflicted by other systematic errors. The tangential distortion may for
instance be mentioned.