Rangefinder



A rangefinder is a device that measures distance from the observer to a target.

Techniques
Some devices use active methods to measure (such as sonar, laser, or radar); others measure distance using trigonometry (stadiametric rangefinders and parallax, or coincidence, rangefinders). Older methodologies that use a set of known information, usually distances or target sizes, to make the measurement, have been in regular use since the 18th century.

Applications
Applications includes surveying, navigation, determining focus in photography, choosing a golf club, or accurately aiming a weapon.

Ballistics
Rangefinders may be used by military or law enforcement snipers as a means of finding the distance to the target in order to set up a "perfect shot". If range is not known before the first shot, it may be necessary to walk the rounds in on the target, such as using tracer ammunition or observing splashes. The laser rangefinder is not always the best option though, as it sends out a light source that may give away the rangefinder's position.

Photography
A rangefinder camera is a camera fitted with a rangefinder which allows the photographer to measure the distance to the subject and thus take photographs that are in sharp focus. Most modern cameras have automatic-focus capabilities.

Forestry
Rangefinders are also 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.

Ballistics

 * Army Test and Evaluation Command, Aberdeen Proving Ground Maryland (1969) Laser Rangefinders Ft. Belvoir Defense Technical Information Center, U.S. Army, Ft. Belvoir, Virginia,  20 pages (early history of the use of lasers in rangefinders)
 * Gething, Michael J. (1993) Airborne Weapons: A Defence Handbook: A compilation of articles from Defence magazine over the last five years, charting the development of Airborne Weapons since 1987 Cardiff Publishing Company, Englewood, Colorado, ISBN 1-881289-11-7, 44 pages
 * Infantry and Cavalry School (1905) Notes on rangefinders, compasses and on contouring with the Scale of Horizontal Equivalents (series: Infantry and Cavalry School Lectures 1902-1910) Staff College Press, U.S. Army, Fort Leavenworth, Kansas,, 35 pages

Photography

 * 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,, 14 pages
 * Hicks, Roger and Schultz, Frances (2003) Rangefinder: Equipment, History, Techniques Guild of Master Craftsman, Lewes, United Kingdom, ISBN 1-86108-330-0

Surveying

 * Ehlert, Detlef; Adamek, Rolf and Horn, Hans-Juergen (2009) "Laser rangefinder-based measuring of crop biomass under field conditions" Precision Agriculture 10(5): pp. 395–408
 * Infantry and Cavalry School (1905) Notes on rangefinders, compasses and on contouring with the Scale of Horizontal Equivalents (series: Infantry and Cavalry School Lectures 1902-1910) Staff College Press, U.S. Army, Fort Leavenworth, Kansas,, 35 pages
 * Whitehouse, J. C. (2005) "Further considerations of defocus rangefinders" Transactions of the Institute of Measurement and Control 27(4): pp. 297–316

Virtual space

 * Ward, A.; Jones, A and Hopper, A. (1997) "A New Location Technique for the Active Office" IEEE Personal Communications 4(5): pp. 42–47
 * Werb, J. and Lanzi, C. (1998) "Designing a positioning system for finding things arid people indoors" IEEE Spectrum 35(9): pp. 71–78