Stadiametric rangefinding

Stadiametric rangefinding

Stadiametric rangefinding, or the stadia method is a technique of measuring distances with a telescopic instrument. The term stadia comes from a Greek unit of length. Stadiametric rangefinding is used for surveying and in the telescopic sights of firearms, artillery pieces, or tank guns, as well as some binoculars and other optics. It is still used in some light equipment, but in many professional applications it has been replaced with microwave, infrared, or laser rangefinding methods.


The stadia method is based upon the principle that in similar triangles homologous sides are proportional. This means that, for a right triangle with a given angle, the ratio of adjacent side length to opposite side length (see sine) is constant. By using a reticle with marks of a known angular spacing, the principle of similar triangles can be used to find either the distance to objects of known size or the size of objects at a known distance. In either case, the known parameter is used, in conjunction with the angular measurement, to derive the length of the other side.

Since a radian is defined as the angle formed when the length of a circular arc equals the radius of the circle, a milliradian (sometimes called a mil), is the angle formed when the length of a circular arc equals 1/1000 of the radius of the circle. An object 5 meters high, for example, will cover 1 mrad at 5000 meters, or 5 mrad at 1000 meters, or 25 mrad at 200 meters. Since the radian expresses a ratio, it is independent of the units used; an object 6 feet high covering 1 mrad will be 6000 feet distant.


Stadia readings used in surveying can be taken with modern instruments such as transits, theodolites, plane-table alidades and levels. When using the stadia measuring method, a "stadia rod" is held so that it appears between two "stadia marks" visible on the instrument's reticle. The stadia rod has measurements written on it that can be read through the telescope of the instrument, providing a known length for the distance calculations.

An instrument equipped for stadia work has two horizontal stadia marks spaced equidistant from the center crosshair of the reticle. The interval between stadia marks in most stadia instruments gives a "stadia interval factor" of 100. The distance between the instrument and a stadia rod can be determined simply by multiplying the measurement between the stadia hairs (known as the stadia interval) by 100.

The instrument must be level for this method to work directly. If the instrument line of sight is inclined, the horizontal and vertical distance components must be determined. Some instruments have additional graduations on a vertical circle to assist with these inclined measurements. These graduated circles, known as "stadia circles", provide the value of the horizontal and the vertical measurements as a percentage of the direct stadia measurement.

This system is sufficiently precise for locating topographic details such as rivers, bridges, buildings, and roads when an accuracy of 1/400 is acceptable.

The stadia method of distance measurement is primarily historical for surveying purposes, as distance nowadays is invariably measured by electronic or taping methods. Total station instruments do not have stadia lines marked on the reticle. Traditional methods are still used in areas where modern instruments are not common or by practitioners whose primary task is not surveying with sophisticated instruments.

ee also



#Raymond Davis, Francis Foote, Joe Kelly, "Surveying, Theory and Practice", McGraw-Hill Book Company, 1966 LC 64-66263

External links

* [ The Stadia]
* [ "Technique of Fire"] , Ch. 5 of "US Army FM 23-11: 90mm Recoilless Rifle, M67" — demonstrates stadiametric rangefinding in an anti-tank weapon sight
* [ MILS and MOA - A Comprehensive Manual to Understanding: types of "Mils", types of Minute of Angle (moa), the Derivation of The Range Estimation Equations by Robert J. Simeone]

Wikimedia Foundation. 2010.

Игры ⚽ Поможем написать курсовую

Look at other dictionaries:

  • Telescopic sight — Scope redirects here. For other uses, see Scope (disambiguation). View through a 4x rifle scope. A telescopic sight, commonly called a scope, is a sighting device that is based on an optical refracting telescope. They are equipped with some form… …   Wikipedia

  • Stadium (disambiguation) — Stadium (Latin) or stadion (Greek) has the plural stadia in both Latin and Greek. Stadia (Anglicized in translation in many sources) refers to a unit of length, the Stadion of ancient greece. 2Stadium may refer to:* Stadium, a building type (the… …   Wikipedia

  • Angular mil — An angular mil, also mil, is a unit of angle. All versions of the angular mil are approximately the same size as a trigonometric milliradian. Contents 1 History 2 Mathematical principle 3 Use …   Wikipedia

  • Stadia mark — Stadia marks, also called stadia lines or stadia hairs, are crosshairs on the reticle of a theodolite or other surveying instrument that allow stadiametric rangefinding.EtymologyThe term stadia mark derives from the obsolete unit of distance, the …   Wikipedia

  • Reticle — Crosshairs redirects here. For the fictional characters in Transformers, see Crosshairs (Transformers). A comparison of different reticles used in telescopic sights. The lower right represents a reticle found in the scope of a Russian SVD sniper… …   Wikipedia

  • Coincidence rangefinder — American soldiers using a coincidence rangefinder with its distinctive single eyepiece during army maneuvers in the 1940s …   Wikipedia

  • Radian — For other uses, see Radian (disambiguation). mrad redirects here. For millirads, see Rad (unit). An angle of 1 rad …   Wikipedia

  • Sako TRG — Infobox Weapon name= Sako TRG caption=Finnish Defence Forces Sako TRG 42 rifle (8.6 TKIV 2000) origin=flag|Finland type= Sniper rifle is ranged=yes service= 2000 present used by= See operators and civil users wars= Afghanistan War, Iraq War… …   Wikipedia

  • Brügger & Thomet APR308 — Infobox Weapon name=APR caption= origin=flag|Switzerland type=Sniper rifle is ranged=yes service= used by=See Users wars= designer=Brügger Thomet design date=2003 (APR308) 2007 (APR338) manufacturer=Brügger Thomet production date=2005 (APR308)… …   Wikipedia

  • ARMA 2 — ArmA II European cover Developer(s) Bohemia Interactive Studio Publisher(s) …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”