In the '90s I used to fly light aircraft back and forth between Seattle and Alaska. You were frequently out of range of any VOR transmitters, but that LORAN always worked. NDBs? That didn't work so great for Ron Brown.
However, in a modern commercial aircraft, all position sources including VOR-DMEs, GPS, and IRS are cross-compared by the flight management system and turned into a latitude, longitude, and circular error of probability. There is no TO/FROM flag to worry about in a 777, and no reverse sensing on the back side of a localizer approach.
It's really hard to jam oceanic areas though, you need a vessel capable of sustaining human life autonomously at least for days plus dealing with the high seas.
Buoys could theoretically be used for that purpose, yes, but good luck getting them stationary enough. Maybe some of the secret services could pull off such a trick but at least no ordinary civilian.
Not really. Drone ships are very much a thing these days.
Although that approach depends on you being able to see the ground neither of which is guaranteed over a body of water or in poor visibility.
https://en.wikipedia.org/wiki/Transcontinental_Airway_System
and have giant concrete QR codes
As more and more are decommissioned, the percentage that support distance-measuring goes up, as the ones being decommissioned are more likely to be the less-useful ones, which are less likely to have supported DME in the first place. So most remaining ones support both, but it’s not assured without checking.
There's GPS jamming by the military, mostly in war zones. This seldom effects airliners because they steer clear of active war zones.
Then there's GPS jamming by delivery drivers who don't want their boss watching over their shoulder all the time. When the article mentions jammers as small as a cellphone and costing less than $100, those are sold to drivers.
Delivery drivers don't jam LORAN or VOR, though - so it's not jammed by the second type.
Btw, don't smartphones have this built in? I remember some old and cheap Android phones without GPS that came with this.
Sounds like the root cause to me. It should be illegal to use GNSS to track employees, or anyone really.
Jamming is starting to sound a lot like self-defense against surveillance.
The plane reported GPS signal loss 5 minutes after the jamming started by WSMR. Three other planes in the area also reported GPS loss.
https://www.stripes.com/theaters/us/2026-08-05/ntsb-medevac-...
That one’s going to be on the flight crew, not the GPS jamming test.
HN discussion: https://news.ycombinator.com/item?id=49181099
One is to actually jam the signal IOW preventing reception. The other is to overpower the satellites' signals and replace them with your own. That defeats the doppler calculations of GPS needed for triangulation, and instead the receiver believes it's where the jammer wants it to be.
If the latter includes altitude information, then it's a huge problem.
If you can say, "oh we were only jamming" when in fact you were spoofing, well that's certainly a super easy excuse to hide behind.
Received GNSS power is on the order of -130dBm (10e-16 W) - you can jam that with a 1W terrestrial source for hundreds of meters around. Way more if you're willing to scale the power from car USB power levels to bigger grid-connected supplies.
LORAN, from my quick googling, looks to be about 6-7 orders of magnitude higher received power.
GPS signals are just incredibly weak so it takes next to nothing to drown them out, easier still if you are above the receiver.
https://news.ycombinator.com/item?id=49186101
https://news.ycombinator.com/item?id=49184484
GPSJam: Daily maps of possible GPS interference - https://news.ycombinator.com/item?id=37868106 - October 2023 (89 comments)
GPSJam: Daily Maps of GPS Interference - https://news.ycombinator.com/item?id=32245346 - July 2022 (82 comments)
https://en.wikipedia.org/wiki/Transmitter_hunting | https://en.wikipedia.org/wiki/Pseudo-range_multilateration | https://www.arrl.org/direction-finding
GPS was jammed even as early as Iraq war.
"Coalition troops also got a glimpse of GPS’s greatest weakness during the Gulf War. Iraqi forces installed jammers, for example, on top of landmarks such as Saddam Hussein’s palaces to prevent them from being hit, Mastalir says. This helped the military realize early on that it would have to further develop its laser-guided munitions and other weapons that acquire targets when GPS is unavailable"
https://web.archive.org/web/20160208233555/http://www.scient...
What work is done to make GPS more jam resistant?
https://insidegnss.com/onenav-l5-direct-technology-enables-d...
For obvious reasons hard information about all this is tricky to come by, you can read what is available from non-classified sources though and you can glean quite a bit from there.
https://en.wikipedia.org/wiki/GPS_signals#L5
The third edition of 'Kaplan' is still excellent reading on the subject even though it is 10 years old now.
Impressive performance.
Single element antennas, adaptive antennas, beam steering antennas. Basically attempting to pull good RF while avoiding bad RF.
(this has been applied in the Russo-Ukrainian war in modified Starlink equipment)
GPS antenna mods make Starlink terminal immune to jammers - https://news.ycombinator.com/item?id=39616417 - March 2024 (72 comments)
https://olegkutkov.me/2023/11/07/connecting-external-gps-ant...
https://www.gpsworld.com/todd-humphreys-russian-satellites-a...
With a quick calculation 50 ms time offset would mean about 20 meter difference. You can get that accuracy with NTP over residential internet and a better TCXO could hold that for a day. You could sync clocks and download the almanac at each airport. The almanac could be digitally signed and NTP has an option for authentication, too. That's about 10 USD of hardware (plus what you need for image capture and processing).
I'm pretty sure with dedicated hardware and better solutions you could get much better accuracy.
[0] https://www.righto.com/2026/04/B-52-star-tracker-angle-compu...
So GPS-like systems need precise orbital data and coherent clock from each satellites, or otherwise the receiver cannot figure out those radii.
Presumably you can have each sats reflect a clock from the same master ground station but that's not how GPS is implemented currently.
And, there's a contextual difference here between civilian GPS and military GPS. Much of the precision in the existing GPS satellites is to support the military use of GPS, with intentionally error injected into the civilian side.
And, by the nature of the hostile environment the military operates, military craft don't have as strong of a reliance on something that's ephemeral, like a GPS signal on a battlefield.
https://www.ti.com/product-category/clocks-timing/clock-netw...