Double circle
The double circle is an innovation in geodetic instrument making , which was introduced around 1935 at the Swiss company Kern Aarau by the inventor and designer Heinrich Wild .
The partial circles of the new theodolite series DK (for double circles) were given a second graduation concentrically attached to the edge of the glass circles (scored, later etched, now manufactured using computer-aided manufacturing ). Their purpose is twofold:
- A quick, but more accurate reading of the circle through optical coincidence , in that two opposite points of the pitch circle are mapped onto one another and reflected in the reading microscope
- less influence of inevitable, small eccentricities of the circles.
The new design was realized for the first time in the miniature theodolite DKM1 (for double-circle micrometers ) and in the second theodolite DKM2 ; Since the 1960s , based on this principle, the series of DKM2-A as well as DKM3 and DKM3-A, which is still unsurpassed in terms of accuracy, has been developed (the attached A means the astrogeodetic applicability through a special telescope construction).
Other manufacturers ( Wild-Heerbrugg , Zeiss, Topcon etc.) have developed similar circular divisions, but automated the readout a little earlier than Kern. Today, both Kern and Wild are part of the Leica Group.
See also
- Reading , circular division machine
- Horizontal angle measurement, simultaneous measurement
- Universal instrument
literature
- Franz Ackerl : Geodesy and photogrammetry , 1st part: instruments and methods of measurement , instruments for angle measurement (p.119, 120, 236). Georg Fromme & Co., Vienna 1950