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GP: Fachverband Geschichte der Physik

GP 4: Instruments and Measurement

GP 4.2: Vortrag

Dienstag, 17. März 2026, 17:15–17:45, KH 02.019

Stereoscopic Rangefinders: in the Borderlands Between Physics and Physiology — •Andreas Junk — Europa-Universität Flensburg

The development of the stereoscopic rangefinder is the strange story of an improvement of precision in range determination by introducing a notoriously unprecise element: an observer. After the identification and introduction of the personal equation in astronomy in the first half of the 19th century it was clear, that the human factor cannot possibly be removed from any measurement made by a human operator. The resolution in that particular case was to find methods to remove the human error by mathematical means. The subsequent idea of precision measurement, which were intiated based on the findings of Bessel in astronomy, was to an extent to not let an operator have an influence in any precise measurement, i.e. to remove the operator from the measurement.

In the last decade of the 19th century the newly developed rangefinders were pushing the limits of precision engineering but they were facing very basal problems regarding the uncertainty of the measurement. The geometrical principles of physics and engineering indicated, that the error to be expected in distance measurement couldn't be ruled out by precise manufacturing or an improved design of the instrument. The development of the stereoscopic telemeter was not only an attempt to overcome this particular problem, it added insult to injury by re-introducing the human operator, whose daily experiences gave the grounds to improve the measurements at large distances.

Keywords: history of science; precision measurements; parallactic shift; distance measurement; stereoscopy