be always on the same level.
But there is the problem of the instrumental equi-
pment and suitable aids. Among the common facilitiers of
the laboratories we usually find the magnifying glasses,
stereoscopes with paralax bar, and different kinds of
sketchmasters. As to the magnifying glasses, a special
Mautner magnifying glass should be mentioned, which has
illumination and double magnifying and which has been
produced in the german Democratic Republic. As the ste-
reaoscopes are regarded, for practical education pur -
poses, the double Old Delft Scanning Stereoscope is ve-
ry useful, as well a stereoscope WILD ST 10. Another ne-
cessary equipment, that is not too expensive, are the
light tables, normal and colour composite viewers, pro-
jectors such as Reflecting projektor Keuffel and Esser
Company, Itek Corp. or stereoprojection viewers, for
example DOT Products Inc. Projekting equipment is for
the purpose of instruction very suitable, because it
enables the interpretation to be presented for a large
number of students.
The only special instrument for interpretation, rat-
her more expensive than the mentioned equipments is at
present Interpretoscope Carl Zeiss Jena, which has found
favour within rather a short time. The observing system
of the instrument, with two eyepieces, is equipped with
a transfocator enabling the 2,5 up to 15 magnifying.
There is the possibility for two workers, to observe
at the same time and the stereoscopic viewing of roll
film strips.
A well equipped laboratory of today should have al-
so a densitometr with registration, electro-mechanical
device as TGZ 3 Carl Zeiss Oberkochen, for counting the
quantity of different objects for analyzing visible
facts in the aerial photograph, and others. The equip-
ment like that is of course more expensive.
Not less expensive are the special apparatuses pro-
cessing the sattelite images. There is a number of in-
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