Air Traffic Radar. A basic view

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Air traffic radar

helps the ground control team direct aircraft, both in the air, like in the worldwide air traffic video above, and while moving about on land.  Air traffic controllers use the radar information to keep aircraft properly separated.

To do this, they use mathematical formulas. And the calculations make aircraft separation possible in 3 dimensions: laterally, longitudinally, and vertically.

Air traffic radar enables split-second computations needed for decision making. The system helps controllers determine which instructions to send. Potentially dangerous air traffic situations can be diverted, hazardous weather systems noted, and relevant information transmitted to pilots and crew.

Today, much of the air to ground information is sent by computer links. This cuts down on the errors that come from miscommunication between the air traffic controller and pilots.

What happens with the air traffic radar data

The information from radar and flights shows up on electronic screens. This also allows the relay of greater amounts of data in less time.

Air traffic control needs primary and secondary air traffic radar displays to keep track of the air planes and watch the weather. The secondary or beacon air traffic radar is usually attached to the same pole as the primary radar and they work in a synchronous fashion.

Radar information provides supporting knowledge necessary to prepare clearance information to relay to aircraft. Controllers then issue advisories and instructions to both instrument and visual flight rules (IFR and VFR) airplanes. The traffic advisories compiled by use of radar information may list altitudes, ranges and the bearings of aircraft located in close proximity to other flight paths.

Knowing and using this data helps avoid collisions by directing aircraft to maintain separation from other craft within their air space.

How the information gets around

Every aircraft returns an echo of the primary signal after the primary radar sends out a high frequency signal burst.  It works much like a weather radar detecting precipitation.  This allows the controller to know where each aircraft is located and then track its path.  Planes with transponders aboard can reply to the beacon as well.  

A special device queries the aircraft and receives vital information.  A stream known as the Mode C signal pulse gets the current altitude of the plane.  Mode A obtains its identity.

The transponder can automatically transmit a coded reply to the Mode C query. The Mode A query must be answered by a specific code with 4 assigned numbers manually entered by the pilot.

Radar helps air traffic controllers calculate ground speed, assess the current air traffic situation, such as monitoring for heavy air traffic and tracking each plane's magnetic headings.

Air traffic radar Display

The radars automatically display electronically mapped and calculated flight plans for every plane. Radio signals can be used to calculate altitudes, speeds, directions, and locations of planes. This same radar technology delivers similar information on ships, cars, and storms. The transmitter for the radar will send out short, high frequency radio pulse waves which bounce off of the target object. This frequency pulse lasts for a fraction of a second and the transmitter then closes while the receiver opens to receive the echo.

When signals get back to the receiver, the radar determines the length of time it took for the return signal. Some radar equipment calculates a Doppler shift in the echoed signals. Analyzing these measurements gives the location and the flying speed of the tracked aircraft.

To recap: the radar antenna sends out pulses of radio waves to the aircraft and it picks up the weaker returned signals. Even with weak radio waves or signals being returned, it is easy to process the information with the use of amplification as radio waves are easy signals to amplify.

Go back from Air Traffic Radar to the Radar Real Time Weather web page.

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