[realcertify]

For the past 10 years I've been travelling to Russia occasionally. Normally during a flight I like opening up my GPS app to check the location, altitude and speed of the aicraft.

About a year ago I noticed that shortly after crossing Russias border the GPS stopped working. Initially I thought it was a glitch, but after a few flights it became obvious that something was going on, probably the signal was baing jammed.

Interesting that close to landing when the altitude is lower than 200m, the signal is restored.

It's unclear to me how the plane is navigating though if the GPS is jammed. Very weird...

[jandrewrogers]

Planes have used inertial navigation for a long time. Adding GPS to that mix is relatively recent. GPS was never really intended to be used for navigation even though it can be and often is. There was no need for it to be particularly reliable when it was designed since the Soviets could easily kill it if they wanted to. It had a different purpose.

[AlotOfReading]

Can you elaborate on what you mean by "not intended for navigation"? GPS was intended as a replacement for TRANSIT and LORAN, which have navigation literally in their names. It's also the textbook example on Wikipedia's satellite navigation page, and I can't imagine how precise geolocation somehow wouldn't be useful for navigation.

Also, the general analysis after KAL007 was that GPS should be made publicly available specifically to aid civilian navigation. They even identify what we call RAIM today to make it suitable for eventual usage as a primary navigation system.

[jandrewrogers]

GPS was trivially attackable from inception, that was not a design requirement given its purpose. The purpose of GPS was to precisely measure the planet in peacetime. A unique core capability of the US military is extremely precise INS technology, the capabilities and precision of which are closely guarded secrets and under continuous R&D. The precision of INS is dependent on the precision of your world model. GPS allowed extremely precise world models to be built globally, which provided the data model INS needs to be maximally effective. In wartime the GPS system can be killed by any near-peer adversary, but the damage has already been done to the extent inertial targeting systems have a precise model of the world.

No US military system relies on GPS for navigation. Military navigation systems use GPS as an untrusted source for fine-tuning inertial navigation within tight error bounds. Against US military systems, successfully spoofing GPS might buy you several meters of deviation. This only affects the cheapest US guidance systems, since most weapons have active terminal guidance. It is worth noting that GPS corrections are being phased out in US weapon systems, purportedly due to improvements in INS tech that moot the value of GPS corrections.

The tl;dr: GPS was developed to build a precise model of the world in peacetime that could be fed to inertial targeting and navigation systems in the complete absence of GPS. In that, it has been a massive success. US military systems have never relied on GPS for anything important. Contrary to popular media, the US has never produced GPS-guided weapons, even the cheapest systems are INS at their core.

Civilian systems use GPS for navigation, against its design, because they can mostly ignore its trivial susceptibility to hostile actors.

[AlotOfReading]

Most of the basic attacks against GPS also worked against TRANSIT, LORAN, OMEGA, and others, which were clearly used for military navigation. I'm not seeing the design differentiation with the systems that were guiding ships and missiles.

[jandrewrogers]

All US military navigation systems use INS pervasively for primary navigation. You can attack GPS, LORAN, etc and it won't affect their operations. This has been axiomatic in the design of those systems for many decades. US military ships are no different, also using INS for primary navigation. As with every other US military system, they can conditionally accept fine-tuning inputs from GPS and other untrusted sources of navigation data because why not. They use a lot of open source data sources, but they don't need them or trust them.

[burnerthrow008]

> It's unclear to me how the plane is navigating though if the GPS is jammed. Very weird...

RNAV (or aRea Navigation) based on VOR-DME has been a thing since (at least) the 1970's. You put in a waypoint based on a radial and distance from a navaid, and then the box in the cockpit would Do Math so you could follow a track to/from that virtual navaid.

Bendix even made a cute little box for small airplanes in the 1980's that allowed you to pre-store up to 4 (or 10) such waypoint-frequency tuples and cycle through them to approximate a straight path from your origin to destination, using navaids near (but not on) your route. Given the service volume of a typical VORs, the 10 waypoints could enable a flight segment of over 2,000 km before you needed to enter more waypoints.

Around the same time, the flight management systems in airliners began to have navaid databases, allowing you derive lat/lng from the angle and distance. They could even auto-select the best local navaid to use. That enabled DME-DME area navigation, which has ~10x better precision than VOR-DME.

The flight management systems in modern airlines of course still have these databases and support navigation by ground-based navaid.

Russia still operates their version of LORAN (Chayka), too, so that's another option. By the 1980's, LORAN receivers were pretty well automated and directly produced lat/lng outputs. LORAN has worse accuracy than GPS, about ~400 meters, but is still good enough to get you to the airport.

And, as several other people have mentioned, virtually all airliners continue to carry an INS.

[coredog64]

GPS isn’t the only navigation tool. INS is pretty accurate if you zero it correctly, and VOR is good enough to keep to a specific airway.

[glitchc]

All INSes require periodic GPS updates to limit the growth of positional error. Usually it's once per second or once every 10th of a second.

[numpad0]

That sounds way too frequent, isn't typical holdover like 12 hours?

[dataflow]

This? https://www.defenseone.com/defense-systems/2023/12/russia-ja...

As for planes, can they do GLONASS?

[realcertify]

My phone is supposed to support GPS, Glonass, Beidou and Galileo, so apparently all of them were jammed.

[dataflow]

I guess it would make sense if they were all jammed, though I'm not sure the fact that your phone didn't pick those up really proves this was the case? I have no idea how these work but I could totally imagine phones interpreting jammed signals differently from weak/nonexistent ones. Plus, I've had at least one that nominally supported all of those but in practice didn't really feel that way. You're probably right, just not sure you can deduce it from your phone in particular.

[upbeat_general]

I would imagine any military “GPS Jammer” would also block similar systems…

[jccooper]

If you know GPS is unreliable in specific areas, it's not hard to get around with rough accuracy. There's still a compass, after all.