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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 (military), director and radar, which is designed to assist a ranged weapon system to target, track, and hit a target. It performs th ...
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 more specialized roles in surface warfare such as naval gunfire support (NGFS) and anti-aircraft warfare (AAW) engagements. T ...
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 ) is the horizontal angle from a cardinal direction, most commonly north, in a local or observer-centric spherical coordinate system.
Mathematically, the relative position vector from an observer ( origin) to a point ...
or 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 naval warfare, maritime military branch, service branch of the United States Department of Defense. It is the world's most powerful navy with the largest Displacement (ship), displacement, at 4.5 millio ...
's s). Warships had plotting rooms for naval fire control for guns from 5-inch to 18-inch calibre
In guns, particularly firearms, but not artillery, where a different definition may apply, caliber (or calibre; sometimes abbreviated as "cal") is the specified nominal internal diameter of the gun barrel bore – regardless of how or wher ...
, including anti-aircraft
Anti-aircraft warfare (AAW) is the counter to aerial warfare and includes "all measures designed to nullify or reduce the effectiveness of hostile air action".AAP-6 It encompasses surface-based, subsurface ( submarine-launched), and air-ba ...
use for the smaller guns. On armoured ships such as battleship
A battleship is a large, heavily naval armour, armored warship with a main battery consisting of large naval gun, guns, designed to serve as a capital ship. From their advent in the late 1880s, battleships were among the largest and most form ...
s and cruiser
A cruiser is a type of warship. Modern cruisers are generally the largest ships in a fleet after aircraft carriers and amphibious assault ships, and can usually perform several operational roles from search-and-destroy to ocean escort to sea ...
s, plotting rooms were located in the armoured citadel, protected by both deck and belt armour. With a few exceptions (mostly in Scandinavia), coastal defence 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 Coast Artillery fire control system, fire control system to track the observed course of a target (typically a moving ship), project its future p ...
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. For antiaircraft applications they were used in conjunction with a director compu ...
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 stations (usually colocated with observation equipment in a two-story structure), taller fire control towers, 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
In the U.S. Army Coast Artillery Corps, the term fire-control system, fire control system was used to refer to the personnel, facilities, technology and procedures that were used to observe designated targets, estimate their positions, calculate ...
* Seacoast defense in the United States
Seacoast defense was a major concern for the United States from its independence through 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 armie ...
References
{{reflistExternal links
Coast Defense Study Group website
Coastal artillery Artillery operation Naval artillery Naval anti-aircraft guns