DKM1
DKM1 is the name of a theodolite made by the Swiss company Kern Aarau and stands for double-circle micrometer theodolite . It was developed in the 1930s by the precision mechanic Heinrich Wild and for a long time was the smallest geodetic measuring instrument designed as a travel theodolite .
Despite its height of only about 13 cm, it was more precise than the considerably larger building theodolites of other instrument manufacturers, which was mainly due to Wild's invention of the double circle principle for the pitch circles for direction and height measurement. She improved the circle reading noticeably. Instead of a circular division, the DKM1 received two on each of the two glass circles, which were scored concentrically (later photo-mechanically etched).
As a further innovation, instead of the usual vertical foot screws in the substructure of the theodolite , Kern-Aarau designed three adjusting screws with a horizontal axis and hospital groove, which reduced the overall height by a few centimeters.
The further development to the more precise, only slightly larger second theodolite was named DKM2 . However, since the small size of an instrument is not always an advantage in rough everyday surveying, the follow-up model DKM2-A , which was launched on the market in the 1960s, was designed again with almost the industry-standard height of around 20 cm.