FlightAware Discussions

GPS, ADS-B May Be Out In Southeast US During 'Interference Tests' Feb 2019


Testing started yesterday 6 Feb 2019. Article below and link to FAA Advisory is in the article.


Thinking about how I might see impacts in the ADS-B data. Anything large/obvious may be easy to see, but more subtle things I’m not so sure how they would show up. I wonder if the ADS-B accuracy/uncertainty/integrity fields would change when GPS interference is active.



Aren’t they exactly for that? Displaying ANP (actual navigation performance)?

As for ADS-B interference, if the interference transmitter is not airborne you have a good chance of not having it in view just like an aircraft on the ground.
Then your station should not be affected.


Yeah, we do see the accuracy metrics drop off when there’s GPS jamming around. Different transponders / avionics setups behave in different ways when they lose GPS entirely so you might see some drop back to dead-reckoning data while others just stop transmitting positions entirely.


Hopefully Galileo will come online next year. It will provide an alternative to the US GPS system.

Not sure how many avionics receivers can use it. Most recent mobile phones support it(https://galileognss.eu/is-your-phone-using-galileo/). Avionics take much longer to update, test and certify.



When I first read about these fields I guessed they were for nominal conditions. I guessed that they reflected a combination of how good the hardware set was, and/or how many satellites it was receiving. But just guessing.

I’m going to go back in ICAO 9871 (2012 edition) to see how they define these fields and if they touch on the impact of ‘interference’. On a quick look, I don’t see this, but I need to go back and take a slower more careful look.

Thanks for the discussion.



Results from Android App GPSTest on my phone:



No Galileo or SBAS satellites received.
Your device may not support them.

I use a GPS receiver for NTP on an RPI. Pretty good accuracy, but needs a better ethernet port.


Examples of GPS jammingruv1el4dtx3nxvan4e3xeyfuvxa



How do you know it was GPS jamming? Just curious


At least in one case, Northrop Grumman RQ-4 Global Hawk flew not far from here.