Originally Posted by
jimjim1
I have no idea where they get the data. I notice that Dave mentions Radar, however other discussion groups mention a different adsb radio frequency than used by "airline" grade (let me call it:-) adsb. There is certainly accurate looking height data. I think you can get that from a radar transponder.
Someone said:- "The C152 was pinging on 978mhz.
978 MHz is a reference to UAT (
Universal Access Tranceiver) - an alternative (in the USA) to the more common 1090 MHz Extended Squitter. For either to be used for ADS-B (i.e. tracking) requires the aircraft to be equipped (usually) with a GPS source. Whether or not fitted with GPS, the aircraft will still send altitude data via Mode C or Mode S.
A number of the services we commonly use like FlightAware can't see 978 signals unless the plane is closer to 1800' in the Watsonville area"
Don't confuse what's available to crowd-sourced tracking sites like FlightAware or FR24 with what ATC (and hence the NTSB) has access to.