"Dave Butler" wrote in message
news:1119360496.186398@sj-nntpcache-3...

Isn't the source of the traffic information the same for both TIS (mode-S)
and TIS-B (the traffic part of ADS-B)?

Yes and no.

TIS is entirely Mode S based. It uses Mode S as a source to identify the
traffic near you and Mode S datalink service to uplink the data to your
aircraft.

TIS-B uses both Mode S and UAT. Source data may be either ADS-B data or
Mode S surveillance data. The Mode S data is converted to ADS-B format
(lat, lon, alt, ID) by the ground system. Since very few people are ADS-B
equipped, most of the TIS-B data being broadcast is converted Mode S
surveillance.

What is it that's being decommissioned? Is it the mode-S (which TIS-B
doesn't use) transmitters? ...or is the data being cut off at the source?


I'm assuming that the 'decommissioning' of TIS is being driven by bean
counters with the maintenance budget. Either that or it's a case of a 'this
program is just too cheap, it can't be any good' mentality at the FAA.
After all, it cost less than $2.5M to put in the system nationwide. It's
not much more than a $10K workstation with a pretty much autonomous
software application plugged into the Mode S ground station.

Gerry