![La_Corbière_range_finder](https://upload.wikimedia.org/wikipedia/commons/8/81/La_Corbi%C3%A8re_range_finder.jpg)
A rangefinder (also rangefinding telemeter, depending on the context) is a device used to
measure distances to remote objects. Originally optical devices used in
surveying
Surveying or land surveying is the technique, profession, art, and science of determining the terrestrial two-dimensional or three-dimensional positions of points and the distances and angles between them. A land surveying professional is ca ...
, they soon found applications in other fields, such as photography and in the military. They were specially useful for finding the range of a target, such as in
naval gun
Naval artillery is artillery mounted on a warship, originally used only for naval warfare and then subsequently used for naval gunfire support, shore bombardment and anti-aircraft roles. The term generally refers to tube-launched projectile-firi ...
nery and
anti-aircraft artillery
Anti-aircraft warfare, counter-air or air defence forces is the battlespace response to aerial warfare, defined by NATO as "all measures designed to nullify or reduce the effectiveness of hostile air action".AAP-6 It includes surface based, ...
. The word ''telemeter'' is derived .
Designs
![Graf Spee telémetro 01](https://upload.wikimedia.org/wikipedia/commons/8/83/Graf_Spee_tel%C3%A9metro_01.jpg)
The first rangefinder telemeter was invented by
James Watt
James Watt (; 30 January 1736 (19 January 1736 OS) – 25 August 1819) was a Scottish inventor, mechanical engineer, and chemist who improved on Thomas Newcomen's 1712 Newcomen steam engine with his Watt steam engine in 1776, which was fun ...
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
hairs
Hair is a protein filament that grows from follicles found in the dermis. Hair is one of the defining characteristics of mammals.
The human body, apart from areas of glabrous skin, is covered in follicles which produce thick terminal and f ...
in the focal plane of a telescope
eyepiece
An eyepiece, or ocular lens, is a type of lens that is attached to a variety of optical devices such as telescopes and microscopes. It is named because it is usually the lens that is closest to the eye when someone looks through the device. The ...
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.
Several others have been credited with the invention of the rangefinder telemeter at one time or another. The
Royal Society of Arts
The Royal Society for the Encouragement of Arts, Manufactures and Commerce (RSA), also known as the Royal Society of Arts, is a London-based organisation committed to finding practical solutions to social challenges. The RSA acronym is used m ...
gave an award to W. Green for its invention in 1778, even though they were made aware of Watt's priority.
In 1778,
Georg Friedrich Brander
Georg Friedrich Brander (* 28. November 1713 in Regensburg; † 1. April 1783 in Augsburg) was an important maker of scientific instruments.
Early years
Brander was born 1713 to Georg Brandner, an apothecary with roots in Nuremberg, and Sibylla ...
invented the
coincidence rangefinder
A coincidence rangefinder or coincidence telemeter is a type of rangefinder that uses mechanical and optical principles to allow an operator to determine the distance to a visible object. There are subtypes split-image telemeter, inverted image, ...
. 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
Jesse Ramsden FRS FRSE (6 October 1735 – 5 November 1800) was a British mathematician, astronomical and scientific instrument maker. His reputation was built on the engraving and design of dividing engines which allowed high accuracy measure ...
invented a half-image range finder. Though
Alexander Selligue is often mistakenly credited with the invention, he did invent an improved telemeter with fixed lenses in 1821 and is responsible for coining the term.
In 1899,
Carl Pulfrich
Carl P. Pulfrich (September 24, 1858 in Burscheid, Rhine Province – August 12, 1927 in Baltic Sea, drowned when his canoe capsized) was a German physicist, noted for advancements in optics made as a researcher for the Carl Zeiss company in ...
at
Carl Zeiss AG
Carl Zeiss AG (), branded as ZEISS, is a German manufacturer of optical systems and optoelectronics, founded in Jena, Germany in 1846 by optician Carl Zeiss. Together with Ernst Abbe (joined 1866) and Otto Schott (joined 1884) he laid the f ...
fabricated a practical
stereoscopic rangefinder
A stereoscopic rangefinder or stereoscopic telemeter is an optical device that measures distance from the observer to a target, using the observer's capability of binocular vision. It looks similar to a coincidence rangefinder, which uses differen ...
, based on a patent of Hector Alexander de Grousilliers.
World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
era telemeters 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
In trigonometry, a skinny triangle is a triangle whose height is much greater than its base. The solution of triangles, solution of such triangles can be greatly simplified by using the approximation that the sine of a small angle is equal to that ...
. 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. The baseline required for the telemeters for battleship guns is very large. More modern telemeters use an electronic technology such as
laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The fir ...
s or
radar
Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...
.
Applications
Applications include
surveying
Surveying or land surveying is the technique, profession, art, and science of determining the terrestrial two-dimensional or three-dimensional positions of points and the distances and angles between them. A land surveying professional is ca ...
,
navigation
Navigation is a field of study that focuses on the process of monitoring and controlling the movement of a craft or vehicle from one place to another.Bowditch, 2003:799. The field of navigation includes four general categories: land navigation, ...
, to assist focusing in
photography
Photography is the art, application, and practice of creating durable images by recording light, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film. It is employed ...
, choosing a
golf club
A golf club is a club used to hit a golf ball in a game of golf. Each club is composed of a shaft with a grip and a club head. Woods are mainly used for long-distance fairway or tee shots; irons, the most versatile class, are used for a variety ...
according to distance, and correcting aim of a projectile
weapon
A weapon, arm or armament is any implement or device that can be used to deter, threaten, inflict physical damage, harm, or kill. Weapons are used to increase the efficacy and efficiency of activities such as hunting, crime, law enforcement, s ...
for distance.
Golf
Laser rangefinder
A laser rangefinder, also known as a laser telemeter, is a rangefinder that uses a laser beam to determine the distance to an object. The most common form of laser rangefinder operates on the time of flight principle by sending a laser pulse in ...
s 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.
Ballistics
Rangefinders may be used by users of
firearm
A firearm is any type of gun designed to be readily carried and used by an individual. The term is legally defined further in different countries (see Legal definitions).
The first firearms originated in 10th-century China, when bamboo tubes ...
s over long distances, to measure the distance to a target to allow for projectile drop. Until the development of electronic means of measuring range during the
Second World War
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
, warships used very large optical rangefinders—with a baseline of many meters—to measure range for naval gunnery.
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
Virtual reality (VR) is a simulated experience that employs pose tracking and 3D near-eye displays to give the user an immersive feel of a virtual world. Applications of virtual reality include entertainment (particularly video games), educ ...
systems to detect operator movements and locate objects.
[Kidd, Cory D. ''et al.'' (1999) "The aware home: A living laboratory for ubiquitous computing research" ''Lecture Notes in Computer Science'' 1670: pp. 191–198, ]
See also
*
GfK-Telemeter, a device to determine the viewing rate
*
Telemeter chronograph
A chronograph is a specific type of watch that is used as a stopwatch combined with a display watch. A basic chronograph has an independent sweep second hand and a minute sub-dial; it can be started, stopped, and returned to zero by successive ...
References
*
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
The Defense Technical Information Center (DTIC, pronounced "Dee-tick") is the repository for research and engineering information for the United States Department of Defense (DoD). DTIC's services are available to DoD personnel, federal governm ...
, U.S. Army, Ft. Belvoir, Virginia, (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,
* Hicks, Roger and Schultz, Frances (2003) ''Rangefinder: Equipment, History, Techniques'' Guild of Master Craftsman, Lewes, UK,
*
* Whitehouse, J. C. (2005)
Further considerations of defocus rangefinders ''Transactions of the Institute of Measurement and Control'' 27(4): pp. 297–316
''Range-Finding in the Army. How to use range-finders to get results: the erect and inverted types,''Popular Science
''Popular Science'' (also known as ''PopSci'') is an American digital magazine carrying popular science content, which refers to articles for the general reader on science and technology subjects. ''Popular Science'' has won over 58 awards, incl ...
monthly, February 1919, page 118–120, Scanned by Google Books
*
External links
{{Commonscat, Rangefinders
Rangefinder Comparison - A National Forest Service document
Length, distance, or range measuring devices