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A plotting room was the co-ordination centre of a
/ref>Major Watkin's Position Finder at victorianforts.co.uk
/ref>Watkin depression position finders at victorianforts.co.uk
/ref>
Coast Defense Study Group website
Coastal artillery Artillery operation Naval artillery Naval anti-aircraft guns
A plotting room was the co-ordination centre of a fire control system
A fire-control system (FCS) is a number of components working together, usually a gun data computer, a director, and radar, which is designed to assist a ranged weapon system to target, track, and hit a target. It performs the same task as a h ...
for guns used against enemy ships or aircraft, whether naval gun
Naval artillery is artillery mounted on a warship, originally used only for naval warfare and then subsequently used for shore bombardment and anti-aircraft roles. The term generally refers to tube-launched projectile-firing weapons and excludes ...
s or coastal artillery
Coastal artillery is the branch of the armed forces concerned with operating anti-ship artillery or fixed gun batteries in coastal fortifications.
From the Middle Ages until World War II, coastal artillery and naval artillery in the form of ...
. The plotting room received data on ship or aircraft position and motion from fire control instruments or their operators and determined and transmitted the range and bearing (a.k.a. azimuth
An azimuth (; from ar, اَلسُّمُوت, as-sumūt, the directions) is an angular measurement in a spherical coordinate system. More specifically, it is the horizontal angle from a cardinal direction, most commonly north.
Mathematical ...
or deflection
Deflection or deflexion may refer to:
Board games
* Deflection (chess), a tactic that forces an opposing chess piece to leave a square
* Khet (game), formerly ''Deflexion'', an Egyptian-themed chess-like game using lasers
Mechanics
* Deflection ...
) the guns would fire on. Plotting rooms came into use in the early 1900s for coastal artillery and during World War I for warships as gun ranges increased, and were in general use through the 1970s on World War II-era ships (and into the 1990s on the US Navy
The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...
's s). Warships had plotting rooms for naval fire control for guns from 5-inch to 18-inch calibre
In guns, particularly firearms, caliber (or calibre; sometimes abbreviated as "cal") is the specified nominal internal diameter of the gun barrel bore – regardless of how or where the bore is measured and whether the finished bore match ...
, including anti-aircraft use for the smaller guns. On armoured ships such as battleships and cruisers, plotting rooms were located in the armoured citadel, protected by both deck and belt armour. With a few exceptions (mostly in Scandinavia), coastal defence
Coastal management is defence against flooding and erosion, and techniques that stop erosion to claim lands. Protection against rising sea levels in the 21st century is crucial, as sea level rise accelerates due to climate change. Changes in s ...
gun installations were inactivated shortly after World War II (US) through the middle 1950s (UK). Equipment in plotting rooms included specialised plotting board
A plotting board was a mechanical device used by the U.S. Army Coast Artillery Corps as part of their fire control system to track the observed course of a target (typically a moving ship), project its future position, and derive the uncorrected ...
s and other analogue devices; by World War II these were supplemented or replaced by electro-mechanical gun data computer
The gun data computer was a series of artillery computers used by the U.S. Army for coastal artillery, field artillery and anti-aircraft artillery applications. In antiaircraft applications they were used in conjunction with a director.
Variati ...
s. Data could be received and transmitted by telephone, or directly via dedicated electrical systems. Locations of plotting rooms in coastal defence installations varied greatly; they could be in low-rise structures such as base end station
Base end stations were used by the United States Army Coast Artillery Corps as part of fire control systems for locating the positions of attacking ships and controlling the firing of seacoast guns, mortars, or mines to defend against them. A Brit ...
s (usually colocated with observation equipment in a two-story structure), taller fire control tower
A fire control tower is a structure located near the coastline, used to detect and locate enemy vessels offshore, direct fire upon them from coastal batteries, or adjust the aim of guns by spotting shell splashes. Fire control towers came into g ...
s, in gun battery structures, or in bunkers separate from gun batteries.
The British Watkin position finder system for coastal artillery, which entered service in the 1890s, did not require a plotting room due to mounting a depression position finder (DPF) on a "range dial", similar to a plotting board. An electrical system moved bearing and range dials near the guns as the DPF was manipulated by an operator.Coast defence range finding at victorianforts.co.uk/ref>Major Watkin's Position Finder at victorianforts.co.uk
/ref>Watkin depression position finders at victorianforts.co.uk
/ref>
See also
* Coast Artillery fire control system *Seacoast defense in the United States
Seacoast defense was a major concern for the United States from its independence until World War II. Before airplanes, many of America's enemies could only reach it from the sea, making coastal forts an economical alternative to standing armies o ...
References
{{reflistExternal links
Coast Defense Study Group website
Coastal artillery Artillery operation Naval artillery Naval anti-aircraft guns