Aircraft locations all weird

Can someone help me understand this –

Some days the PIAware aircraft locations are spot on. They land on the proper runway, they go where they are supposed to go.

Then sometimes…they are all over the place. It shows planes landing in a shopping center 1 mile from the airport, or the ocean (yipes!) or flying in the wrong direction. It can be common for the aircraft track to constantly readjust and shift several miles.

Is there a reason for this?


some planes have their ADSB linked to inertial location systems, the gyros are set at takeeoff - but by the time they land they’re just not quite correct.

Wow. I certainly hope that gets fixed before ADSB replaces radar :slight_smile:

The position messages do include some info about the accuracy of the position - generally if an aircraft loses GPS for whatever reason, it does indicate that it’s reporting an INS position or a degraded GPS position by dropping the accuracy reported, and that position data isn’t going to be trusted when it matters.

Here’s what bothers me -
I fly all over this state and my plane’s GPS/internal nav system is never off by more than a foot or two. There are days when my home ADBS can show 50 planes (as in major airlines) off by miles with the icon suddenly shifting to play catch up. That indicates to me a signal or processing problem.

If my auto pilot took me as far off course as some I’ve seen it would be in the shop immediately.


Show me some raw messages that show the problem?

Sure, as soon as I figure how how :slight_smile:
I just run the thing and feed FlightAware.

Lemme see what I can do. I’d like to solve this mystery.

You can connect to port 30002 for raw messages, one line per message.
If you capture that output while you see the problem and search for only lines containing the ICAO address of the aircraft that has the problem (DF17 messages, the position messages, include the address directly, so this is a handy shortcut to narrow it down without requiring full decoding), then those should be enough to work out what’s going on.

It should look something like this (here, I filtered for 4CA61B). The longer messages will be the DF17s.