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  Surveying Instrument Collection 


Tamaya & Co. (Japan)



Serial Number



Circle diameter = 240mm, Length of arms = 400mm (extending from centre of circle)


Micrometer Station Pointer


This instrument is commonly known as a station pointer or a three-arm protractor. It is used in ordinary hydrographic survey work to fix a point from three or more trigonometric stations by resection. Once the necessary angles have been measured with a sextant, the position of a station (eg. a boat), can be located on a chart using this special form of protractor. It consists of a circle, graduated to 30 minutes from 0 to 180 degrees. A divided circle with a diameter of 160mm is equipped with three radial arms extending well beyond its circumference, and the edge of the middle arm is fixed at zero. The other two arms located on either side of the zero arm, are pivoted centrally and feature clamping screws. Also attached to each of these two arms are micrometers to allow for more accurate settings of the measured angles. In order to use the station pointer, the instrument is first placed on the plan, the arms are opened to the two measured angles, and with the bevelled edges of the arms positioned on the three targets (three known points are needed for any resection calculation), the centre of the circle located the position of the station. 

History & comments

The invention of this instrument is generally attributed to the British hydrographer Murdoch McKenzie (died in 1797).


In Aluminium case (L 540mm, H 280mm, W 45mm)


Good condition

  • Each arm can be fitted with extension legs (280 mm long), and there are exactly three of these legs included with the instrument
  • All extension legs are intact
  • This Micrometer Station Pointer is one of two in the collection (see also 0123)
  • Catalogued by T. Ko
  • Updated by F. Pall


Manufactured in 1966. Catalogued in 1997

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