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 celes ...
, 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 measure distances to remote objects. Originally optical devices used in surveying, they soon found applications in other fields, such as photography an ...
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 computer that uses the continuous variation aspect of physical phenomena such as electrical, mechanical, or hydraulic quantities (''analog signals'') to model the problem being solved. In c ...
.
Development and use
The hand held stadimeter was developed by
Bradley Allen Fiske
Rear Admiral Bradley Allen Fiske (June 13, 1854 – April 6, 1942) was an officer in the United States Navy who was noted as a technical innovator. During his long career, Fiske invented more than a hundred and thirty electrical and mechanic ...
(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
A maneuvering board is an aid to navigation. It is typically a writing surface with a pre-printed compass rose of polar coordinates about a central point, often including adjacent linear scales, and sometimes a time/speed/distance nomogram. With th ...
, 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). The two elements are also called the worm screw and worm gear. The terminolo ...
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 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 ...
is inadvisable.
See also
*
Rangefinder
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, they soon found applications in other fields, such as photography an ...
*
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 '' Stadion'' (equal to 600 Greek feet, ''pous'') which was the typical length ...
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