Communication, navigation and surveillance (CNS) are the main functions that form the infrastructure for

air traffic management file:ATMANS.png, 334x334px, Air traffic management (ATM) aims at ensuring the safe and efficient flow of air traffic. It encompasses three types of services: * air traffic services (ATS) including air traffic control (ATC), air traffic advisory s ...

, and ensure that air traffic is safe and efficient.

Functions

The CNS has the following three main functions.

Communication

Communication, i.e. aviation communication, refers to communication between two or more aircraft, the exchange of data or verbal information between aircraft and

air traffic control Air traffic control (ATC) is a service provided by ground-based air traffic controllers who direct aircraft on the ground and through a given section of controlled airspace, and can provide advisory services to aircraft in non-controlled air ...

and the ground based communication infrastructure of the ATM network (like the aeronautical fixed service). For continental airspace, VHF (civil) and

UHF Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter ...

(military) systems are used whereas for oceanic areas,

high frequency High frequency (HF) is the ITU designation for the band of radio waves with frequency between 3 and 30 megahertz (MHz). It is also known as the decameter band or decameter wave as its wavelengths range from one to ten decameters (ten to one ...

systems and SATCOMs are used.

Navigation

Navigation, i.e.

air navigation The basic principles of air navigation are identical to general navigation, which includes the process of planning, recording, and controlling the movement of a craft from one place to another. Successful air navigation involves piloting an airc ...

, refers to the process of planning, recording, and controlling the movement of an aircraft from one place to another by providing accurate, reliable and seamless position determination capability.

Surveillance

Surveillance systems are used by air traffic control to determine the position of aircraft. There are two types of surveillance systems:

Cooperative systems

Cooperative systems: Under this form of surveillance, systems on the ground (such as SSR) communicate with equipment (such as

transponder In telecommunications, a transponder is a device that, upon receiving a signal, emits a different signal in response. The term is a blend of ''transmitter'' and ''responder''. In air navigation or radio frequency identification, a flight trans ...

s) on board the aircraft to determine the position and other details of the aircraft. Aircraft information, which may include position from

GNSS A satellite navigation or satnav system is a system that uses satellites to provide autonomous geopositioning. A satellite navigation system with global coverage is termed global navigation satellite system (GNSS). , four global systems are op ...

or other means is determined on board and then transmitted to ATC in response to interrogation. Other cooperative systems such as ADS-B rely on aircraft transmitting their position and other information without interrogation from the ground.

Non-cooperative systems

Non-cooperative systems: Under this form of surveillance, systems on the ground (such as PSR) are able to locate the aircraft and measure its position from the ground by transmitting pulses of radio waves which reflect off the aircraft's hull.

References

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