Sources of track data (TA, TZ) in the US

FlightAware AeroAPI
1

When I fetch a track from GetHistoricalTrack, each point has a field updateType. I know from http://discussions.flightaware.com/post143420.html that a value of TA in this field means ‘sourced from ADS-B packets’, and TZ means ‘sourced from radar’

I have two questions about TA & TZ …

  1. How do you decide which to use ? Would I be right in thinking that you use ADS-B data when you have it, and fall back to Radar when you don’t ?

  2. Where does ‘radar’ data come from, in the USA ? Do you source it from the FAA ? Is it realtime ? (I’ve heard that the FAA has realtime radar data, 5m-delayed data, and that they also publish an overnight dump of ‘cleaned up’ radar data, but I might be wrong on all of this)

Thanks !

2

  1. Correct. If we have recent ADS-B data then it will be preferred over Radar because the data is more timely and the position accuracy is much better. Radar positions are increasingly less accurate the further the plane is from the radar antenna.

  2. In the U.S., the radar data comes from the FAA ASDI feed, which is delivered to us 5 minutes delayed. There has historically been an option to qualify for a “class 2” ASDI feed which is not delayed, but that requires us to undergo additional infrastructure security auditing and we probably would not be able to publicly disclose that realtime data to the general public.