"dpb" wrote in message
...
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Watching your local Doppler radar feed is the best bet and your best
chance of somehow automating something would be to figure out a way
to tie into that feed and utilize it...which isn't all that bad an
idea, actually, now that you've prompted it.

When we were developing a component of ADS-B the engineers added a
feature to filter out approaching aircraft warnings until they came
within 20(?) miles of the unit's GPS location.
http://en.wikipedia.org/wiki/Automat...ance-broadcast

http://en.wikipedia.org/wiki/Reverse_911

jsw