Maritime patrol

Maritime patrol is the task of monitoring areas of water. Generally conducted by military and law enforcement agencies, maritime patrol is usually aimed at identifying human activities.

Maritime patrol refers to active patrol of an area, as opposed to passive monitoring systems such as sound-detection fixtures or land-based spotters. A patrol consists of a ship, submarine, aircraft or satellite examining the patrolled area and seeking out activities to be identified and reported. Maritime patrol is critical in wartime situations for navies to locate enemy forces to engage or defend against. Peacetime patrols are important for interdiction of criminal activities and for ensuring legal use of waters.

Maritime patrols can be conducted by surface ships and submarines, by aircraft and other aerial vehicles, and even by satellites. Human spotting remains an important part of detecting activity, but increasingly electronic systems are used.

Several types of maritime patrol missions exist:

• Military: Navies and air forces employ patrols to locate and identify enemy or potential enemy ships and submarines. The patrols report these findings to combat vessels which can then take appropriate action. Characteristics to identify are the numbers and types of vessels, as well as bearing and speed information to assist tracking the units. Anti-submarine patrols often deploy sonobuoys or other devices to assist with tracking. During peacetime, patrols are maintained by military forces for practice and to prevent surprise deployments by enemies.

• Law enforcement: Countries with extensive coastlines are vulnerable to those entering or exiting the country undetected. In particular smuggling is often carried out over water. Law enforcement agencies often employ maritime patrols to assist interception of such activities.

• Economic: Water areas, in particular those close to the coast, are areas of economic activity. Not only shipping but also fishing and even tourism are important economic activities to coastal countries. Patrolling these waters falls to maritime patrols. Such patrols may seek fishing vessels which are outside of prescribed fishing grounds (often from neighboring countries' fleets) or which are not adhering to regulations. Additionally, patrols may assist customs agencies by monitoring commercial shipping traffic in controlled waters.

• Coast defence: Coast defence identifies and intercepts threats to coastal areas. This may include preventing infiltrations or discouraging enemy surveillance of coastal installations. Law enforcement patrols aim at preventing criminals from reaching the shoreline.

• Rescue: Although not necessarily a primary mission of maritime patrol assets, they are often used to assist in maritime rescue operations, both for searching and often to extract survivors too.

Maritime patrols are conducted by all manner of ships, aircraft, and other assets:

• Surface ship: The most traditional form of maritime patrol is to send out ships to sail the seas and report their findings. Generally smaller vessels with limited combat ability are employed, so that larger numbers can be acquired and thus larger expanses can be covered. Sophisticated electronics are installed to increase these units' efficiency. Despite limited armament, such vessels are usually capable of engaging enemy patrols and defending to some degree from air attack. Patrol vessels are often specialized for a certain type of mission, such as anti-submarine patrol. Surface ships are also heavily used for law enforcement.

• Submarine: Surface vessels are vulnerable to enemy naval forces, as well as to air attack. To offset this, submarines came into use as patrol vessels for missions farther from home waters. Submarines also carry torpedoes which allowed them to exploit opportunity targets better than most other patrols. Unfortunately, their limited sensors above the surface cut down on the amount of surface they can cover at any given time. Submarines are generally only used for military patrol missions.

• Aircraft: Patrol was one of the first roles for aircraft at sea, with larger ships equipped with small planes for use as scouts. Generally aircraft carried by ships are used for patrol of the waters around the ship to prevent enemy ships and submarines from getting near. Carriers use such patrols to identify targets for air strikes. Larger land-based aircraft are capable of patrolling for long distances and maintaining their patrols for many hours. However, aircraft are limited in the amount of armaments they carry, instead relying on airstrikes by other planes to attack targets. Due to their high point of view and fast speed, aircraft can cover large expanses of water quickly. Anti-submarine patrol is a common task for maritime patrol aircraft.

• Helicopter: Helicopters have an ability to hover which allows them to scan the surface and to drop sensors into the water to search underwater. Their small size and lack of need for landing space also makes them ideal for employment on ships. However, helicopters have limited range, and cannot maintain long endurance patrols like land-based aircraft. Helicopters are heavily employed in law enforcement patrols.

• Satellite: The value of satellites for maritime patrol was quickly grasped as a satellite has the ability to monitor any patch of water immune to enemy attack. Sensors can identify activities on the surface and underwater. Limitations exist: satellites may not be in proper position when needed, or a country may simply lack enough to cover the desired areas. They are very expensive and only a few nations can afford sufficient coverage. Additionally they are subject to interference both by weather patterns and by human countermeasures.