Hi. I have been sharing data with popular websites for three years. I have noticed a strange situation for several weeks. Various planes appear periodically at a distance of 328 nm:
My receiving radius is 220-230NM and I think this is an error. But what can it be caused by if I haven’t changed anything in the settings or the installation itself recently? My antenna is suspended about 13 m above the ground. Its model is: Vinnant CC1090/9-P. I also use the Uputronics 1090 amplifier. The gain in the Skyaware tab is set to 25,4 dB.
My config:
This can occur due to atmospheric conditions from time to time.
This effect is known as “ducting”, the signals can bounce further due to cloudlayers or other atmospheric changes.
I would remove your FR24 configuration screenshot, your sharing key is yours only, you shouldn’t share that key
Ducting usually needs a body of water nearby the antenna.
GDS spoofing sounds more likely. Nasty business.
The “aircraft” (as in what is displayed to the pilots) very likely knows the correct position due to GPS disagreeing with the INS and INS probably superseding the wildly wrong GPS (one would hope).
Still surprised ADS-B standards require the GPS position to go directly to the transponder, seems like a weird design choice.
Would be interesting to check the tracks for the aircraft in question on the aggregators.
So … screenshot with a time and the aircraft selected so the hex number shows?
I agree on the GPS spoofing as an option as well.
There have been multiple reports on that matter coming from the Baltic region and the surrounding countries
You are in the general vicinity of a lot of military activity so GPS jamming/spoofing will unfortunately be the norm. I’ve seen the same over the Baltic states for quite a while now. One thing that has gotten “better” is FA and FR24 seem more adept at falling back to MLAT to produce more realistic tracks than the nonsense noted in your examples. Quite common for me to pick up an aircraft as MLAT over Estonia/Latvia then have it transition to ADS-B once it leaves the impacted area.
FR24 just released a a GPS jamming map on their site. And there is also gpsjam.org. Not to keep plugging a FA competitor, but this recent podcast on FR24 dealt with the spoofing problem (approximately last 30 minutes of podcast). These resources may help you understand more on what is going on. Always something new to learn with this hobby!
Always look for ‘something else’ that is NQR as a plausibility check.
As above, when you can catch one in the act, check it on other receivers / sites to see if you have a consensus on location.
AIS transponders are the same. They are required to have their own dedicated GPS receiver, you can’t feed position data to them via NMEA. I think the purpose is to avoid the introduction unintentionally incorrect data.
The thing with ads-b is it at least transmits quality of fix data so ground stations can determine whether they are getting an accurate position. They can then decide at what level of accuracy degradation they disregard the data.
If you allow other systems to feed or modify the position data being transmitted, you can get questionable data without knowing that it’s questionable. For example, an aircraft broadcasting a fix from an INS that hasn’t had an update for several hours could have drifted significantly, or a fix derived from VOR beacons only could be of questionable accuracy depending on range and geometry of the beacons used.
Well it would still be a better position than a spoofed position.
And the accuracy metric should of course still be at the lowest possible level when the source isn’t direct from GPS.
