Geodetic Theodolite
notes: label: Description
content: This theodolite was designed in 1924 by Douglas L. Parkhurst, chief of the Instrument Division of the U. S. Coast and Geodetic Survey. It was made by August Heim, an instrument maker who worked with Parkhurst and contributed several ideas to its development. It was completed in July 1927. The horizontal circle is silvered, graduated to 5 minutes, and read by two micrometer microscopes to single seconds..The signature reads "U. S. C. & G. S. No. 308."
label: Description
content: Aiming to produce an instrument suitable for first-order geodetic work, Parkhurst was concerned that there be "no appreciable change in the fit of the vertical axis bearing due to changes in temperature," and no frictional drag between the telescope alidade and the graduated circle. Moreover, he wrote, "The entire design must be made with a view to ruggedness and speed of manipulation and to provide for simple and easy adjustment under field conditions." By 1928 Parkhurst could boast that "field tests" had proven his theodolite "to be one of the most accurate, rapid and durable instruments" that the Survey had ever used.
label: Description
content: Ref: Douglas L. Parkhurst, "A New First Order Theodolite," <i>Journal of the Franklin Institute</i> (1928): 624–629.
label: Description
content: Douglas L. Parkhurst, "Unusual Design in New Theodolite," <i>Engineering News–Record</i> 101 (1928): 806–808.
label: Location
content: Currently not on view
setName: label: See more items in
content: Medicine and Science: Physical Sciences
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content: Surveying and Geodesy
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content: Measuring & Mapping
publisher: label: Related Publication
content: Engineering News-Record
label: Related Publication
content: Journal of the Franklin Institute
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: PH.314801
label: accession number
content: 206598
label: catalog number
content: 314801
objectType: label: Object Name
content: geodetic theodolite, Parkhurst
physicalDescription: label: Measurements
content: overall: 20 in; 50.8 cm
label: Measurements
content: horizontal circle: 9 in; 22.86 cm
label: Measurements
content: vertical circle: 6 in; 15.24 cm
label: Measurements
content: telescope: 12 in; 30.48 cm
label: Measurements
content: striding level vial: 4 in; 10.16 cm