Bridge (nautical)
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The bridge of a ship is an area or room from which the ship can be commanded. When a ship is underway, the ship's captain or a senior officer is on the bridge at all times to maintain command and control.
[edit] Evolution
Traditionally, in sailing ships, the ship would be commanded from the poop deck, right aft. With the arrival of paddle steamers, engineers required a platform from which they could inspect the paddle wheels and the captain required a position where his view would not be obstructed by the paddle houses. A raised walkway, literally a bridge, connecting the paddle houses was therefore provided. When the screw propeller superseded the paddle wheel, the bridge was retained.
Traditionally, commands would be passed from the senior officer on the bridge to stations dispersed throughout the ship, where physical control of the ship was exercised, as technology did not exist for the remote control of e.g. steering or machinery. Helm orders would be passed to an enclosed wheel house, where the coxswain or helmsman operated the ship's wheel. Engine commands would be relayed to the engineer in the engine room by an engine order telegraph, which displayed the captain's orders on a dial. The engineer would ensure that the correct combination of steam pressure and engine revolutions were applied to enact his orders. The bridge was often open to the elements, therefore a weatherproof pilot house could be provided, from where a pilot (traditionally, the pilot was the ship's navigating officer) could issue commands from shelter.
Iron, and later steel, ships also required a compass platform. This was usually a tower, where a magnetic compass could be sited as far away from the ferrous interference from the hulk the ship. Depending upon the design and layout of a ship, all of these terms can be variously interchangeable. Many ships still have a flying bridge, a platform atop the pilot house, open to weather, containing a binnacle and voice tubes to allow the conning officer to direct the ship from a higher position during fair weather conditions.
Larger ships, particularly warships, often had a number of different bridges. A navigation bridge would be used for the actual conning of the ship. A separate Admiral's bridge could be provided in flagships, where the Admiral could exercise strategic control over his fleet without interfering with the Captain's tactical command of the vessel. In older warships, a heavily-armoured conning tower was often provided, where the vital command staff could be located under protection to ensure that the ship could be commanded and fought under fire.
Modern advances in remote control equipment has seen progressive transfer of the actual control of the ship to the bridge. The wheel and throttles can be operated directly from the bridge, directly controlling often-unmanned machinery spaces.