Stadimeter
Hand-held optical rangefinder using known object height.
A stadimeter estimates the distance to an object whose height is already known. It does this by measuring the angle formed between the object’s top and bottom as seen through the device. Like a sextant, it uses mirrors to measure an angle between two points, but unlike a sextant, the user first dials in the object’s height. Because it is compact, it works well as a hand-held tool or inside a submarine periscope. It qualifies as an analog computer and belongs to the broader family of optical rangefinders.
The hand-held version was invented by United States Navy officer Bradley Allen Fiske. Though intended for gunnery, its first sea trials in 1895 proved equally valuable for formation sailing and navigation. It was typically stored on the bridge and used there or on the bridge wings to maintain proper spacing between warships steaming in formation or in convoys. The Navy Bureau of Ships placed multiple orders for hand-held stadimeters starting shortly after their development in the late 1890s. By the early 1900s, the device—along with the sextant, spyglass, maneuvering board, parallel motion protractor, and other navigation tools—was standard equipment for a US warship’s navigation officer.
During World War II, the Mark 5 version was redesigned to operate more like a sextant. It replaced the linear screw worm drive, which set the object’s height, with a single pivot arm. This change allowed faster measurements of multiple objects with different heights, since the slow worm drive no longer needed adjustment for each new height; instead, a quicker adjustable arc arm set the object’s height before taking a sight. Today, the stadimeter remains in use aboard US Navy warships when active radar is not advisable.
- type
- Optical rangefinder
- inventor
- Bradley Allen Fiske
- inventor_nationality
- United States Navy officer
- first_sea_tests
- 1895
- primary_use
- Gunnery, fleet sailing, navigation
- later_version
- Mark 5 (World War II)
Lore & Background
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.
Reader's Guide
The stadimeter represents a significant development in naval navigation and gunnery, providing a portable means of range estimation without active emissions. Its hand-held design and use of a known object height made it ideal for submarines and bridge use. The United States Navy Bureau of Ships contracted for orders starting shortly after its development in the late 1890s, and by the early 1900s it was standard gear for navigation officers. During World War II, the Mark 5 version replaced the linear screw worm drive with a single pivot arm, allowing faster measurement of multiple objects of differing heights. Today it is still used aboard US Navy warships at times when using active radar is inadvisable, underscoring its enduring utility as a passive ranging tool.
Did You Know?
- The stadimeter is similar to a sextant but differs in that one dials in the height of the object.
- It was developed by United States Navy officer Bradley Allen Fiske.
- Its first sea tests in 1895 showed it was useful for both gunnery and fleet sailing.
- The Mark 5 version during World War II replaced the linear screw worm drive with a single pivot arm.
Frequently Asked Questions
What is a stadimeter?
A stadimeter is a compact optical rangefinder that calculates how far away an object is by measuring the angular span between its top and bottom, provided the object's actual height is already known. It functions as a type of analog computer and sits within the broader family of optical ranging devices.
Who invented the hand-held stadimeter?
The hand-held version was created by Bradley Allen Fiske, an officer in the United States Navy. His design first went through sea trials in 1895.
How does a stadimeter differ from a sextant?
Both instruments use mirrors to capture the angle between two points, but a stadimeter requires the operator to first dial in the known height of the target object. This extra input lets the device convert that angle directly into a distance reading rather than just reporting the angle itself.
What was the stadimeter primarily used for?
Its main applications were in naval gunnery, fleet navigation, and general sailing. Because of its small size, it also fit neatly inside submarine periscopes, making it a versatile hand-held ranging tool.
What later version of the stadimeter saw military service?
The Mark 5 variant was the model deployed during World War II. It carried forward the original principle of using a known object height and mirror-based angle measurement to produce quick distance estimates in combat and navigation settings.
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