A stadimeter is an optical device for estimating the range to an object of known height by measuring the angle between the top and bottom of the object as observed at the device. It is similar to a

sextant A sextant is a doubly reflecting navigation instrument that measures the angular distance between two visible objects. The primary use of a sextant is to measure the angle between an astronomical object and the horizon for the purposes of cel ...

, in that the device is using mirrors to measure an angle between two objects but differs in that one ''dials in'' the height of the object. It is one of several types of optical

rangefinder 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, suc ...

s, and does not require a large instrument, and so was ideal for hand-held implementations or installation in a submarine's

periscope A periscope is an instrument for observation over, around or through an object, obstacle or condition that prevents direct line-of-sight observation from an observer's current position. In its simplest form, it consists of an outer case with ...

. A stadimeter is a type of

analog computer An analog computer or analogue computer is a type of computation machine (computer) that uses physical phenomena such as Electrical network, electrical, Mechanics, mechanical, or Hydraulics, hydraulic quantities behaving according to the math ...

Development and use

The hand held stadimeter was developed by Bradley Allen Fiske (1854–1942), an officer in the United States Navy. It was designed for gunnery purposes, but its first sea tests, conducted in 1895, showed that it was equally useful for fleet sailing and for navigation. It was normally kept on the bridge and used from there and on the bridge wings to keep warships at the proper distance from one another when steaming in formation and for use in convoys. The United States Navy Bureau of Ships contracted on several occasions for orders of hand-held stadimeters starting shortly after its development in the late 1890s. By the early 1900s it along with the sextant, spyglass, maneuvering board, parallel motion protractor and other navigation tools were part of the standard gear for the navigation officer aboard US warships. During World War II the Mark 5 version was developed to function more like a sextant, with a single pivot arm replacing the linear screw

worm drive A worm drive is a gear arrangement in which a worm (which is a gear in the form of a screw) meshes with a worm wheel (which is similar in appearance to a spur gear). Its main purpose is to translate the motion of two perpendicular axes or to t ...

which set the height of the object. The primary benefit of this development was that multiple objects of differing heights could be measured much faster since it removed the slow moving worm drive, which would need to be adjusted for each object height before a sight was taken with a much faster adjustable arc arm to set the object's height. Today it is still used aboard US Navy warships at times when using active

radar Radar is a system that uses radio waves to determine the distance ('' ranging''), direction ( azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track ...

is inadvisable.

References

External links

{{commons category, Stadimeters
A hand-held stadimeter; information and photos
Naval weapons of the United States Length, distance, or range measuring devices de:Schnittbildentfernungsmesser

Development and use

See also

References

External links