Old 3rd Feb 2019, 08:35
  #983 (permalink)  
Join Date: Jan 2008
Location: Reading, UK
Posts: 10,565
Originally Posted by ATC Watcher View Post
With a mode S return you can very accurately calculate the ground speed and the final rate of decent
I'm still struggling to understand how that can be so. Can you explain further ?

You said previously that you were talking about Mode S and not ADS-B, but basic Mode S only gives you surveillance ID (squawk) and altitude (DF5 and DF4, respectively).

So, yes, you can calculate RoD, but the download data contains no velocity information so I don't see how it's possible to derive GS.

Originally Posted by ATC Watcher View Post
I noticed the BEA said it will be concentrating the research within 4 square miles, so here you go.
No doubt that's true, but the estimate of final position could well have come from primary radar (possibly military?), rather than SSR.
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