Würdemann Six-inch Theodolite

This six-inch theodolite was used by the Coast and Geodetic Survey in the mid to late 19th century. With its 11-inch telescope, this instrument was tiny next to earlier theodolites.

Würdemann Six-inch Theodolite

Image courtesy of the Smithsonian National Museum of American History.

Made by William Würdemann sometime between 1849 and 1881 and designated "No. 163," this theodolite is tiny compared to Ferdinand Hassler's Great Theodolite. A thing of beauty, made of brass with silvered circles, the telescope is 11 inches long, the horizontal circle six inches in diameter, (making it a six-inch theodolite).

The vertical circle is read, with the help of a magnifier, by a single vernier. A vernier is the auxiliary scale that allows for precise reading of fractional parts of the main circle scale on a theodolite. A pair of opposite verniers read the horizontal circle, which is graduated in single minutes, to single seconds.

Historic Reference

In a March, 1836, letter to the Secretary of the Treasury, first Survey of the Coast Superintendent Ferdinand Hassler pointed out that he needed a "chief mechanician," without which instruments would have to be shipped to Europe for maintenance and repair. He requested that William Würdemann, "a very able man in his line," be appointed to the job full time. Twenty-five years old at the time, the Bremen-born German shared Hassler's standards for quality work, and he crafted numerous instruments for the Survey both during his time of employment and after he left the Coast Survey to begin his own instrument business in 1849.

  • Instrument Shown: Würdemann six-inch theodolite
  • Location: Probably Smithsonian National Museum of American History
  • Manufacture Date: Between 1849 and 1881
  • Dates of Use: Mid to late 19th century
  • Photo Date: Unknown

Works Consulted

Davis, R.E., Foote, F.S., Kelly, J.W. (1966). Surveying: Theory and Practice. New York: McGraw-Hill.

Hassler, F.R. (1820). Principle Documents Relating to the Survey of the Coast of the United States and the Construction of Uniform Standards of Weights and Measures for the Custom Houses and States. Vol. III (pp. 31 and 63).

Smithsonian Virtual Surveying Instrument Collection. Theodolite. Retrieved July 13, 2006, from: http://americanhistory.si.edu/collections/surveying/object.cfm?recordnumber=747933.

Related Web Sites:

Smithsonian Virtual Surveying Instrument Collection

National Geodetic Survey