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The Geodimeter (acronym of geodetic distance meter) was the first optical

electronic distance meter Length measurement, distance measurement, or range measurement (ranging) refers to the many ways in which length, distance, or range can be measured. The most commonly used approaches are the rulers, followed by transit-time methods and the int ...

surveying instrument Instruments used in surveying include: * Alidade * Alidade table * Cosmolabe * Dioptra * Dumpy level * Engineer's chain * Geodimeter * Graphometer * Groma (surveying) * Laser scanning * Level * Level staff * Measuring tape * Plane table * Pole ( ...

. It was originally developed for measuring the speed of light. It was invented in 1947 by and commercialized in 1953 by the

AGA Aga or AGA may refer to: Business * Architectural Glass and Aluminum (AGA), a glazing contractor, established in 1970 * AGA (automobile), ''Autogen Gasaccumulator AG'', 1920s German car company *AGA AB, ''Aktiebolaget Svenska Gasaccumulator'', a ...

(''Aktiebolaget Gasaccumulator'') company of Sweden. It was used in the

Transcontinental Traverse The Transcontinental Traverse (TCT) was a geodetic survey traverse conducted in the Continental United States by the U.S. Coast and Geodetic Survey between 1961 and 1976. It was the most accurate large-area survey ever done prior to Global Positi ...

. The Geodimeter business was acquired by SpectraPrecision which was acquired by

Trimble Inc Trimble Inc. is an American software, hardware, and services technology company. Trimble supports global industries in building & construction, agriculture, geospatial, natural resources and utilities, governments, transportation and others. Trim ...

Electronic mechanism

The mechanism uses a Kerr cell in an optical train that chops a

collimated beam A collimated beam of light or other electromagnetic radiation has parallel rays, and therefore will spread minimally as it propagates. A perfectly collimated light beam, with no divergence, would not disperse with distance. However, diffractio ...

of light under the control of a precision

electronic oscillator An electronic oscillator is an electronic circuit that produces a periodic, oscillating electronic signal, often a sine wave or a square wave or a triangle wave. Oscillators convert direct current (DC) from a power supply to an alternating curre ...

in the megahertz range. It is similar in principle to earlier mechanical choppers in Fizeau–Foucault apparatus that used a toothed wheel or a rotating mirror.

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AGA Geodimeter Model 6
(''Going the Distance: A Photo Collection Illustrating the History of Distance Measurement Tools at the

National Geodetic Survey The National Geodetic Survey (NGS) is a United States federal agency that defines and manages a national coordinate system, providing the foundation for transportation and communication; mapping and charting; and a large number of applications ...

'') 20th-century inventions Surveying instruments Swedish inventions {{Geodesy-stub

Electronic mechanism

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