AGA EDM (Geodimeter Model 4B)
name: label: maker
content: AGA
notes: label: Description
content: The Geodimeter Model 4, introduced in the spring of 1959, measured 12 inches square, weighed about 35 lbs (plus the 12-volt battery and inverter), cost less than $5,000, and had a range of 50 feet to 3 miles. Because of its small size and low cost, it was attractive to independent surveyors, especially when advertisements promised that the initial outlay was "easily returned by the savings gained in just a few projects use." Model 4B was similar to the Model 4, but had a slightly different housing. Model 4D used a high-pressure mercury vapor lamp. Advertisements in 1963 boasted: "Now up to 3 miles in brightest sunshine" and "only one instrument, only one operator."
label: Description
content: In 1965, having found that the Model 4 offered the same accuracy as the Model 2, the U. S. Coast and Geodetic Survey, began phasing out the heavier instrument. The Survey also realized that by equipping a Model 4D with a laser they could increase its range and productivity. George "Bud" Lesley, who had used the Model 2 at Cape Canaveral and several Model 4Ds on the transcontinental traverse, had read up on lasers, and was given the task of designing this modification. Within a year Lesley had replaced the mercury vapor lamp with a 2-mw Perkins-Elmer helium neon laser, replaced the Kerr cell with a KDP cell (an electronic shutter), and replaced the original 1P21 phototube with a 56TVP phototube.
label: Description
content: The Coast and Geodetic Survey then put out a call for someone to put lasers in a number of 4Ds. As the low bidder, AGA got Lesley and his prototype for 60 days, and was soon producing the Model 4L. This instrument required an ac generator, but had a range of 42 km at night, and about 21 km in daylight. On one test in Nebraska, the laser Geodimeter measured a 30-km line, "nearly twice the length of previous measurements, with accuracy exceeding one part in a million."
label: Description
content: A July 14, 1968, press release stated that "A major breakthrough in surveying has been achieved with lasers," and quoted Lesley to the effect that "lasers have enabled survey teams to expand by 20 to 50 percent the amount of terrain covered and to increase their accuracy." For this work Lesley received the Colbert Medal of the Society of American Military Engineers.
label: Description
content: This example is a Model 4B that belonged to the Coast and Geodetic Survey. It is marked "AGA STOCKHOLM SWEDEN X590315 nr 284 NASM-4B." It was made in the period 1960-1964, and was still in use in 1976. The original lamp was replaced with a 2 milliwatt laser in 1969, and a 6 milliwatt laser in 1971.
label: Description
content: Ref: AGA, <i>Geodimeter System Bergstrand Model 4D</i> (March 15, 1964).
label: Description
content: George B. Lesley, "Laser Geodimeter," <i>Surveying and Mapping</i> 27 (1967): 625-631.
label: Location
content: Currently not on view
place: label: place made
content: Sweden: Stockholm, Stockholm
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: AGA. Geodimeter System Bergstrand Model 4D
label: Related Publication
content: American Congress on Surveying and Mapping. Surveying and Mapping
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: 1986.0395.03
label: accession number
content: 1986.0395
label: catalog number
content: 1986.0395.03
objectType: label: Object Name
content: EDM
physicalDescription: label: Measurements
content: overall: 13 in x 12 3/4 in x 19 in; 33.02 cm x 32.385 cm x 48.26 cm