From what I understand, air traffic controllers can monitor planes with radar, often called primary radar, or with ADS-B. I've seen ADS-B called "secondary radar," although it isn't really radar, but I've also seen the phrase "secondary radar" used referring to something that ADS-B replaced. I've also seen references to "SSR" (secondary surveillance radar? just a guess), which also appears to have been replaced by ADS-B.

My understanding:

  1. Primary radar: "normal" radar, similar to what ships have; has been used for a long time and is still used
  2. Secondary radar: originally "SSR"(?); SSR replaced by ADS-B

Is this correct?



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