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Nowadays, There are many surveillance systems other than PSR or SSR, such as ADS-B or MLAT, etc. And ATC system such as ARTS uses various surveillance sensors including ADS-B to indicate track for controller.

But the 'RADAR' means 'Radio detection and ranging'. And I have doubt as to whether this can be included radar category because ADS-B broadcast position of aircraft by using GNSS.

And these are my questions.

  1. Is ADS-B or MLAT RADAR?

  2. When ATC identify aircraft by using ADS-B only, Does controller can say 'Radar contact'?

  3. Can SSR indicate the aircraft position?

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  1. Is ADS-B or MLAT RADAR?

It depends on context, unfortunately. For the purposes of your questions below, the answer is “yes”, as technically wrong as that may be.

  1. When ATC identify aircraft by using ADS-B only, Does controller can say 'Radar contact'?

In the US, yes, because that’s currently the only approved phraseology for controllers to use, even if the contact is not actually from radar.

The ICAO equivalent is “identified”, and the FAA has been gradually coming into compliance with ICAO phraseology, so it’s possible that this will change in the future.

Also, the FAA’s Fusion software takes data feeds from many sources (PSR, SSR, ADS-B, MLAT, etc.) and combines them all into a single display, so the controller may not be aware of which source(s) is(are) providing the target on their screen; all contacts appear to be “radar” contacts.

  1. Can SSR indicate the aircraft position?

Yes. SSR works similarly to primary radar, with a beam sweeping the sky; the two are often combined into a single unit. However, rather than looking for a reflection from the aircraft’s skin, SSR looks for a reply from the aircraft’s transponder. Either way, the azimuth and range of the reply is then translated to a lat/long position.

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  • $\begingroup$ From a terminology standpoint ADS-B is not "radio detection" because it does not search for a target, as PSR/ASR does, but rather waits for the target to announce itself to the receiver. Normal ADS-B is not "radio ranging" either, but you could make an argument that multilateration is. Kind of stretches the definition though, IMO. $\endgroup$
    – randomhead
    Commented May 8, 2022 at 22:08
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  1. Is ADS-B or MLAT RADAR?

No, Automatic Dependant Surveillance Broadcast (ADS-B) and multi-lateration (MLAT) (or the wide-area variety of multi-lateration, WAM) are not radar. They are, like radar, ATC surveillance technologies.

  1. When ATC identify aircraft by using ADS-B only, Does controller can say 'Radar contact'?

That is probably depending on the country. But what is important to understand is that the controller is telling the pilot by 'Radar contact' that they can track where you are based on some kind of surveillance system, and that they can give you instructions based on that position information. To the pilot and air traffic controller, the underlying surveillance technology is of secondary importance.

  1. Can SSR indicate the aircraft position?

Yes, like Primary Surveillance Radar (PSR), Secondary Surveillance Radar (SSR) determines the bearing and range from the radar to the aircraft. In addition it receives, encoded in the reply from the transponder, the altitude (in mode C or Mode S). With this information the position of the aircraft is determined.

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