175
from different countries, mostly in written form, are known at this
moment. Usually they consist of a marking sign, rotating around
the theodolite's vertical axis at a constant speed, which actuates
a pulse counter when passing the direction of reference, and puts
it out of circuit when passing the direction to be measured. One of
the few companies using this principle for the construction of an
instrument is Del Electronics Corp. in Mount Vernon, NY, USA,
but as far as I know it has not been applied to survey work up to
now.
Recently, the Hannover Technological University has developed
an instrument which permits the measurement of angles by mea
suring the speed of a rotating focal plane shutter. Details of this
are given in [34], [35] and [36].
At Bonn University trials were made on angular measurements
by electro-optical means (see for this [37]). The results of these
trials have led to the construction of the digital theodolite "Digi-
gon" by Breithaupt Sohn, Kassei, in cooperation with Leitz,
Wetzlar and Bonn University. The aim is a measuring accuracy of
2 dmgr. Recording of the measured direction is in punched tape,
whilst the value can be read from an illuminated number display.
By these means the objections raised in [31] are met. This permits
the pre-setting of certain angular values.
To increase accuracy and speed of measurement, people in several
countries are working on solutions for photo-electric pointing (ob-
jektive Zielerfassung) along with automatic registration of measure
ments. The results obtained have been modest until now. Publi
cations on this subject are [38], [39] and [40].
Regarding the automation of distance measurement, I only
want to draw your attention to an instrument, newly developed
by Carl Zeiss, the electro-optical distance meter SM 11. Undoubtedly
there is room for some improvements to this instrument. Without
a horizontal and vertical circle, and with its 500 metre range, it
can only be considered as an extremely expensive tape, whose
range of application does not seem to be very great. The instrument
as so far developed, has a number of good points, such as the parti
cularly simple operation, high measuring accuracy, the very handy
illuminated display, and last but not least, the direct recording on
punched tape.
Section 3automation of geodetic (survey) calculations
Though Professor Linkwitz deals with automation of geodetic
(survey) calculations in a separate report, I would like to
devote a paragraph to this subject since it is a logical link between
measuring and plotting.
Automation of calculation in geodesy has progressed much farther
than the other technical activities. In the first place many leading,
and also a number of smaller geodetic (survey) organizations have
purchased a computer. Organizations that cannot afford such
