# How does aviation radar work?

GiTS
I understand the theory of radar but not aviation radar. It is my understanding they can find an objects position in the x, y, and z axis simultaneously. How does that work?

Homework Helper
Most aviation (air traffic control) radar isn't really radar - a radio signal is sent to a transponder on the plane which broadcasts it's own position from the planes GPS, along with it's ID, route, altitude etc

You can determine height (and range) from primary radar by sweeping a narrow beam vertically and measuring the angle at which you get a strong return. Essentially it's just regular radar turned on it's side.

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GiTS
ok. thank you. So how do radar guidance systems or jetplanes find a target in 3 dimensional space? A vertical and horizontal sweeping radar?

Mentor
ok. thank you. So how do radar guidance systems or jetplanes find a target in 3 dimensional space? A vertical and horizontal sweeping radar?

Yes. Either a gimbaled parabolic antenna, or an electrically-steered phased-array antenna. I'll see if I can find some pics...

Mentor
Oh wicked! Looks to be a combination gimballed phased-array antenna in an F-16.

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Homework Helper
ok. thank you. So how do radar guidance systems or jetplanes find a target in 3 dimensional space?
Civil aircraft don't carry primary radar, the position of other planes and the collision avoidance is managed by the transponders.
Large airliners do carry weather radar which is relatively short range and low resolution to pick up rain clouds.

Do planes still use radar altimeters or do they rely on pressure and GPS?

GiTS
Thank you.
I had an idea, but I am not sure if it would work. What if there was one transmitter but 3 receivers spaced out in a triangle. Each receiver would receive the signal at slightly different times if the object was not in between all 3 receivers. Or would the equipment not be fast enough to detect such minute differences?

Homework Helper
You can measure arrival times to incredible accuracy but atmospheric disturbances would be much larger than the difference in arrival time