{{Short description|Device used to measure distances to remote objects}} {{for|the photographic camera|Rangefinder camera}} [[File:Bundesarchiv_Bild_183-J08361,_Entfernungsmesser_einer_Vierlings-Flak.jpg|thumb|Portable stereoscopic rangefinder from WWII]] [[File:Polish destroyer's range-finder.JPG|thumb|The [[coincidence rangefinder]] of the Polish destroyer [[ORP Wicher (1928)|ORP ''Wicher'']]]] [[File:Lightweight Laser Designator Rangefinder, laserowy dalmierz.jpg|thumb|Laser rangefinder]] [[File:La_Corbière_range_finder.jpg|thumb|Second World War German range finding tower at [[La Corbière]], [[Jersey]]]]
A '''rangefinder''' (also '''rangefinding telemeter''', depending on the context) is a device used to [[Length measurement|measure distances]] to remote objects. Originally optical devices used in [[surveying]], they soon found applications in other fields, such as photography, the military, and space travel. They were especially useful for finding the range of a target, such as in [[naval gun]]nery and [[anti-aircraft artillery]]. The word ''telemeter'' is derived {{etymology|grc|''{{wikt-lang|grc|τῆλε}}'' ({{grc-transl|τῆλε}})|distant, far away||''{{wikt-lang|grc|μέτρον}}'' ({{grc-transl|μέτρον}})|something used to measure}}.
==Designs== [[File:Graf Spee telémetro 01.jpg|thumb|Rangefinder salvaged from the [[German cruiser Admiral Graf Spee|German cruiser ''Admiral Graf Spee'']] on display in [[Montevideo]]]]
The first rangefinder telemeter was invented by [[James Watt]] in 1769 and put to use in 1771 in surveying canals. Watt called his instrument a micrometer, a term now used with a different meaning in engineering (the [[micrometer screw gauge]]). It consisted of two parallel [[reticle|hairs]] in the focal plane of a telescope [[eyepiece]] crossing an upright hair. At the point to be measured, two sliding targets on a surveyor's rod were adjusted to align with the hairs in the telescope. The distance to the rod could then be determined from the distance between the targets on the rod by trigonometry.{{sfn|Dickinson|2010|pages=56, 75-76}}
Several others have been credited with the invention of the rangefinder telemeter at one time or another. The [[Royal Society of Arts]] gave an award to W. Green for its invention in 1778, even though they were made aware of Watt's priority.{{sfn|Dickinson|2010|pages=76-77}}
In 1778, [[Georg Friedrich Brander]] invented the [[coincidence rangefinder]]. Two mirrors set a distance apart horizontally in a long slim box, similar to a [[subtense bar]] but located at the measuring station, and forming two images. This rangefinder does not require a measuring rod at the target and could perhaps be considered the first true telemeter. In 1790 [[Jesse Ramsden]] invented a half-image range finder. Though [[Alexander Selligue]] is often mistakenly credited with the invention, he did invent an improved rangefinder with fixed lenses in 1821 and is responsible for coining the term.<ref>Johann Gottfried Dingler, [https://books.google.com/books?id=UlzzAAAAMAAJ&dq=Selligue+telemeter&pg=PA121 ''Polytechnisches Journal''], vol. 8, page 121, Stuttgart: Cotta 1822 {{OCLC|183328327}} (in German)</ref><ref>A. Rittig von Flammenstern, [https://books.google.com/books?id=cywOAAAAYAAJ&dq=Selligue+telemeter&pg=PA561 ''Archiv für Geographie, Historie, Staats- und Kriegskunst''], vol. 13, Franz Härter: Wien, page 561 (in German)</ref>
In 1881, the British [[Royal Artillery]] adopted the [[depression range finder]], which had been developed by Captain H.S.S. Watkin for use by [[coastal artillery]]. It used the measurement of the angle of depression from the observer, sited on a high vantage point, to the waterline of the target vessel.<ref>{{cite book |last=Sambrook |first=Stephen C |title=The Optical Munitions Industry in Great Britain, 1888–1923 |url=https://books.google.com/books?id=gJBECgAAQBAJ&pg=PT27 |year=2015 |publisher=Taylor & Francis |isbn=978-1-317-32103-3 |page=27 }}</ref>
In 1899, [[Carl Pulfrich]] at [[Carl Zeiss AG]] fabricated a practical [[stereoscopic rangefinder]],<ref>Fritz Deumlich, ''Surveying Instruments'', Walter de Gruyter, 1982 {{ISBN|3110077655}}(p.15)</ref> based on a patent of Hector Alexander de Grousilliers.<ref>{{cite patent| country= GB| number= 189317048| status= patent| title= Improved Stereoscopic Telemeter.| gdate= 1894-07-14| fdate= 1893-09-11 | pridate= 1893-09-11| inventor= Hector Alexander de Grousilliers| url= https://worldwide.espacenet.com/publicationDetails/description?CC=GB&NR=189317048A&KC=A&FT=D&ND=3&date=18940714&DB=&locale=#}}</ref>
[[World War II]]-era rangefinders worked optically with two telescopes focused on the same target but a distance apart along a baseline. The range to the target is found by measuring the difference in bearing of the two telescopes and solving the [[skinny triangle]]. Solutions can be obtained automatically, using tables or, rarely, manual calculation. The greater the distance to the target, the longer the baseline needs to be for accurate measurement. Modern rangefinders use an electronic technology such as [[laser]]s or [[radar]].
==Laser rangefinder== {{excerpt|Laser rangefinder}}
==Applications== Applications include [[surveying]], [[navigation]], to assist focusing in [[photography]], choosing a [[golf club]] according to distance, and correcting aim of a projectile [[weapon]] for distance.
===Golf=== Laser rangefinders are used in golf to measure the yardage of a particular shot but also to gauge slope and wind as well. There has been debate over whether they should be allowed in tournaments. While their use is banned on the professional level, they are becoming widely used on the amateur level.<ref>"Golf Rangefinder Comparison Chart at Golfsmith." Golf Rangefinder Comparison Chart at Golfsmith. N.p., n.d. Web. 06 Nov. 2014.</ref><ref>"While We're Young, USGA." Golf.com. N.p., n.d. Web. 06 Nov. 2014.</ref>
===Ballistics=== Rangefinders may be used by users of [[firearm]]s over long distances, to measure the distance to a target to allow for projectile drop.<ref>Farey, Pat and Spicer, Mark (2009) ''Sniping: An Illustrated History'' Zenith Press, Grand Rapids, Michigan, [https://books.google.com/books?id=l1a-kB-1MMAC&pg=PA7 page 7], {{ISBN|978-0-7603-3717-2}}</ref> Until the development of electronic means of measuring range during the [[World War II|Second World War]], warships used very large optical rangefinders—with a baseline of many meters—to measure range for naval gunnery.
=== Archery === In recent decades, laser rangefinders have become popular in [[archery]], especially among [[Bowhunting|bowhunters]].<ref>{{cite web |url=https://www.bowhunter.com/editorial/ulmer-rangefinders-part-1/473277 |title=All You Need to Know About Rangefinders |first=Randy |last=Ulmer |work=Bowhunter Magazine |date=May 11, 2023 |access-date=March 12, 2025}}</ref> Rangefinders marketed for archery use will have angle-compensation features, with an internal computer calculating the horizontal distance to the target. Bowhunters will often shoot from [[Tree stand|treestands]] or in steep terrain, and for relatively short shots (40 yards and under), an archer will need to aim using the horizontal distance instead of the line-of-sight distance.<ref>{{cite web |url=https://www.bowhunter.com/editorial/angle-compensating-rangefinders/477641 |title=Understanding Angle-Compensating Rangefinders |first=Randy |last=Ulmer |work=Bowhunter Magazine |date=June 30, 2023 |access-date=March 12, 2025}}</ref>
===Forestry=== Rangefinders are used for surveying in forestry. Special devices with anti-leaf filters are used.
===Virtual reality=== Since the 1990s, rangefinders have been used in [[virtual reality]] systems to detect operator movements and locate objects.<ref>{{cite book | last1=Kidd | first1=Cory D. | last2=Orr | first2=Robert | last3=Abowd | first3=Gregory D. | last4=Atkeson | first4=Christopher G. | last5=Essa | first5=Irfan A. | last6=MacIntyre | first6=Blair | last7=Mynatt | first7=Elizabeth | last8=Starner | first8=Thad E. | last9=Newstetter | first9=Wendy | chapter=The Aware Home: A Living Laboratory for Ubiquitous Computing Research |editor1-last=Streitz, N.A. |editor2-last=Siegel, J. |editor3-last=Hartkopf, V. |editor4-last=Konomi, S.| title=Cooperative Buildings. Integrating Information, Organizations, and Architecture | series=Lecture Notes in Computer Science | date=1999 | volume=1670 | pages=191–198 |publisher=Springer |location=Berlin, Heidelberg| doi=10.1007/10705432_17 | isbn=978-3-540-66596-0 }}</ref>
==See also== * [[Telemeter chronograph]] * [[Bombsight]] * [[Spotting scope]] * [[Head-up display]]
==References== {{reflist|30em}}
;Sources *{{cite book|last=Dickinson |first=H. W. |date= 2010 |title=James Watt: Craftsman and Engineer |publisher= Cambridge University Press |isbn=978-1108012232}}
==Further reading== * "Range Finder (instrument)." Encyclopædia Britannica Online. Encyclopædia Britannica, * Army Test and Evaluation Command, Aberdeen Proving Ground Maryland (1969) ''Laser Rangefinders'' Ft. Belvoir [[Defense Technical Information Center]], U.S. Army, Ft. Belvoir, Virginia, {{OCLC|227620848}} (early history of the use of lasers in rangefinders) * Photographic and Imaging Manufacturers Association (1999) ''American national standard for photography (optics) : rangefinders and other focusing aids – performance specifications'' (revision and redesignation of "ANSI PH3.619-1988" as "ANSI/PIMA IT3.619-1998") American National Standards Institute, New York, {{OCLC|41501265}} * Hicks, Roger and Schultz, Frances (2003) ''Rangefinder: Equipment, History, Techniques'' Guild of Master Craftsman, Lewes, UK, {{ISBN|1-86108-330-0}} *{{cite book |date=1905 |url=http://www.cgsc.edu/carl/download/lectures/Rangefinders.pdf |title=Notes on rangefinders, compasses and on contouring with the Scale of Horizontal Equivalents |series= Infantry and Cavalry School Lectures 1902-1910 | publisher=Staff College Press, U.S. Army, Fort Leavenworth, Kansas |oclc=278057724 |archive-url=https://web.archive.org/web/20160303193600/http://www.cgsc.edu/carl/download/lectures/Rangefinders.pdf |archive-date=2016-03-03 |via=archive.org}} * {{cite journal |last=Whitehouse |first=J. C. |year=2005 |title=Further considerations of defocus rangefinders |journal=Transactions of the Institute of Measurement and Control |volume=27 |issue=4 |pages=297–316 |doi=10.1191/0142331205tm150oa |bibcode=2005TIMC...27..297W }} * {{cite journal |last=Peterson |first=George M. |url=https://books.google.com/books?id=7igDAAAAMBAJ&pg=PT35 |title=Range-Finding in the Army |journal=[[Popular Science]] |date=February 1919 |volume=94 |issue=2 |pages=18–120 |via=Google Books}} *{{cite web |title=Electro Optic Application Test Equipment |url=http://bnc.helpserve.com/index.php?_m=downloads&_a=downloadfile&downloaditemid=96 |publisher=Berkeley Nucleonics Corporation|archive-url = https://web.archive.org/web/20110711162313/http://bnc.helpserve.com/index.php?_m=downloads&_a=downloadfile&downloaditemid=96|archive-date = 2011-07-11}}
==External links== {{Commons category|Rangefinders}} * [http://www.fs.fed.us/eng/pubs/html/98241307/98241307.html#Intro Rangefinder Comparison - A National Forest Service document]
{{Authority control}}
[[Category:Length, distance, or range measuring devices]] [[Category:Golf equipment]]