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Whats really sad for aviation is there was already an extensive network of ground based navaids. As GPS has proliferated, they've slowly been decommissioned as

Whats really sad for aviation is there was already an extensive network of ground based navaids. As GPS has proliferated, they've slowly been decommissioned as they age out to save on cost. I'm specifically referring to VORs which provide azimuth and range to station. GPS is fantastic and as a primary source everyone loves the benefits it brings. However, in a century of aviation, everyone has kinda sorted out that you can't have too many backups to critical items... unless you let the accountants and bureaucrats run the show.

buildsjets 16d ago
VOR is extremely short range and requires an extraordinary number of transmitters to provide any volume of coverage. Additionally it cannot provide coverage over oceanic areas. We USED TO have a nearly global long-range land based navigation system called LORAN, which only required one master station and a few remote stations to provide continent-scale coverage. But it was decommissioned in a cost savings move after it was determined that it could be replaced by GPS. It worked perfectly fine until it was decommissioned in 2010, not that long ago. 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. https://en.wikipedia.org/wiki/Loran-C https://en.wikipedia.org/wiki/Loran-C
- verelo 16d ago
  On VOR: It's also a PITA to use, and for inexperienced people, or someone who rarely uses it, they can confuse flying towards and away from the station.
  - buildsjets 16d ago
    If you are a general aviation goober like me, flying a 1960's propeller airplane, sure, that is true. 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.
    - verelo 16d ago
      Yeah that makes sense. My experience is mostly in 70s to early 90's prop planes, I have had the opportunity to use a glass cockpit a few times and it was much easier. I guess i did the typical thing and contextualized this on my experiences and ignored that 99.9% of flights are not GA haha.
  - _moof 16d ago
    Time was, if you didn't understand how to use VORs, you couldn't really fly. We used them as primary en route nav, as well as for approaches, for many decades. As a CFI I think most of the confusion around VORs these days comes down to poor or inadequate training.
    - ExoticPearTree 15d ago
      > As a CFI I think most of the confusion around VORs these days comes down to poor or inadequate training. I would say it is partially true. The reason I have trouble with VORs is that the equipment inside the plane is very awkward to use. The fact that the plane is in the center of the VOR display is super confusing as it shows everything in reverse: if the line is on the left it means the plane is on the right. And having to learn Morse Code to validate you tuned in the right frequency. And so on. I get it that when they invented that we did not have technology, but now we do and nothing is stopping us from using a digital display that can translate VORs/DMEs/NDBs fixes into GPS like routes. And knowing where every VOR is can make the map accurate too. That would make it very easy for a lot of people to use and not have to learn the arcane ways of how people used to fly 50 years ago. I don't need to know that I'm flying TO or FROM the station.
    - verelo 16d ago
      That's fair. I replied to someone else with a similar remark, but essentially doing most of my flying in 70s to 90s prop planes, I imagine the tools I'm most used to are just dated. Your point around training is likely very accurate, I had some great teachers but I also had a few instances of being given inaccurate information and having to teach the teacher so to speak.
      - Charon77 16d ago
        I don't fly and I wouldn't call my self someone that plays a lot of flight simulator. But I do enjoy navigation methods and I did learn the basics and practices of VOR navigation. I got an Android app that simulates flying courses, holding patterns etc, but only the navigation part. I would say I learned some intuition to it.
      - 15d ago
- mschuster91 16d ago
  > Additionally it cannot provide coverage over oceanic areas. 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.
  - _moof 16d ago
    > sustaining human life Not really. Drone ships are very much a thing these days.
    - vanviegen 16d ago
      How can a drone ship hold its designated position while it's blocking gps?
      - Intermernet 16d ago
        Astral navigation is probably accurate enough
        K0balt 15d ago
        Dead reckoning with a minute or two to get a gps fix with the jammer off once a day.
        Peanuts99 15d ago
        What's to stop someone spoofing a GPS signal during that fix?
        K0balt 15d ago
        Nothing, and if it were subtle enough it could be effective at making it drift around. Lots of ways to get a rough fix though, and you don’t need very good absolute accuracy offshore, using a compass and log to DR your way around. Even better if you have a wind vane and anemometer. The majority of your drift will be wind driven.
- amelius 15d ago
  Was LORAN also resistant against jamming/hacking?
  - Thorondor 15d ago
    Nothing is completely foolproof, but LORAN is much, much more resistant to jamming than GPS. GPS satellites orbit over 20,000 km from Earth and transmit at very limited power (less than 50 W). That makes it easy to overpower their faint signals. On top of that, GPS operates at a frequency over 1 GHz which means you can broadcast a jamming signal with a small antenna. LORAN is the opposite. It uses low frequency, extremely high power signals transmitted from stations relatively closer to the receiver. Those design choices make it less precise but vastly more robust.
jacquesm 16d ago
And LORAN. But it may make a come-back. GPS signals are just incredibly weak so it takes next to nothing to drown them out, easier still if you are above the receiver.
- toomuchtodo 16d ago
  I would be curious on and interested in guidance from a GNSS expert on what the risk profile is when you're using jam resistant frequencies with a multi GNSS constellation chipset (GPS, Galileo, BeiDou), WAAS (GNSS corrections received via satellite), and when close enough to airports that support it, LAAS (GNSS corrections broadcast from airports). Follow up questions would be what countermeasures are available to bolster GNSS reliability during critical phases of flight (takeoff and landing), as well as how cellular tower networks could be used as distributed sensor fabrics for constantly monitoring for and triangulate GNSS jamming using SDR (or perhaps start with a handful of GNSS reference monitoring stations at major airports for this monitoring). https://news.ycombinator.com/item?id=49186101 https://news.ycombinator.com/item?id=49186101 https://news.ycombinator.com/item?id=49184484 https://news.ycombinator.com/item?id=49184484 GPSJam: Daily maps of possible GPS interference - https://news.ycombinator.com/item?id=37868106 https://news.ycombinator.com/item?id=37868106 - October 2023 (89 comments) GPSJam: Daily Maps of GPS Interference - https://news.ycombinator.com/item?id=32245346 https://news.ycombinator.com/item?id=32245346 - July 2022 (82 comments) https://en.wikipedia.org/wiki/Transmitter_hunting https://en.wikipedia.org/wiki/Transmitter_hunting | https://en.wikipedia.org/wiki/Pseudo-range_multilateration https://en.wikipedia.org/wiki/Pseudo-range_multilateration | https://www.arrl.org/direction-finding https://www.arrl.org/direction-finding https://geodesy.noaa.gov/CORS/ https://geodesy.noaa.gov/CORS/ | https://arcg.is/18fWq8 https://arcg.is/18fWq8
  - leonidasrup 16d ago
    Because GPS and other GNSS have only a very weak signal strength there are no jam resistant frequencies, you can jam them all very efficiently, or you can jam them very efficiently in selective way (jam BeiDou, but not GPS). 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.scientificamerican.com/article/gps-and-the-world-s-first-space-war/ https://web.archive.org/web/20160208233555/http://www.scient...
jshier 16d ago
Seems like we'd need a modern version that's less susceptible to jamming, otherwise aren't we just replacing one jammable service with another?
- michaelt 16d ago
  There are two types of GPS jamming. 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.
  - bb88 16d ago
    GPS jamming was being investigated by the NTSB as a possible reason for this air crash that killed 4 people near White Sands Missile Range. 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-crash-gps-jamming-22466131.html https://www.stripes.com/theaters/us/2026-08-05/ntsb-medevac-...
    - sokoloff 16d ago
      I’d bet a lot of money that the NTSB will determine that the pilots’ failure to maintain clearance from terrain during a visual approach will be the primary cause with contributing factors of dark, moonless night and GPS jamming. That one’s going to be on the flight crew, not the GPS jamming test. HN discussion: https://news.ycombinator.com/item?id=49181099 https://news.ycombinator.com/item?id=49181099
      - bb88 16d ago
        I'm not going to argue that as it's always easy to blame dead people, but there's two different types of jamming. 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.
sokoloff 16d ago
All VORs provide a radial that you’re on. Not all provide a distance to the station. VOR/DME or VORTACs provide both. Plain VORs do not. 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.
- flewbee 16d ago
  By taking a bearing from TWO VORs simultaneously, the distance to each can be computed. That's why planes have two VOR receivers and instruments.
  - sokoloff 15d ago
    Two VOR stations will give you a fix, but since GPS took over from legacy RNAV, that’s now rarely used operationally in the US. More common is to use Nav2 tuned to a VOR to find an intersection on the arrival and Nav 1 to fly the final (ILS/LOC/VOR).
himata4113 16d ago
We have starlink I am sure they can figure something out.
- mschuster91 16d ago
  Starlink lacks the high precision atomic clocks on board of the satellites, that is also why Starlink needs a GPS fix to bootstrap itself.
  - nomel 16d ago
    Maybe the starlink clocks could continuously calibrate from gps? Clock drift is usually a slow thing (like thermals). Their inter-satellite data links have all sorts of relative clocking info.
    - numpad0 16d ago
      IIUC, GPS picks one satellite and 3 more to establish time differences between the first one and the other 3. There's only one point in universe where the set of differences would match what was observed, given the broadcast orbital data of satellites, and that gives the location of the receiver. It's like you are provided radii and center coordinates of 3 circles on a paper that intersect at 1 point and you are to math that point. 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.
      - nomel 16d ago
        Coherency is a state. My question is if that state can be achieved by just tuning the individual clocks/locations based on GPS as a master. And, there's other tricks, with all the inter-satellite communication [1]. 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. [1] https://arxiv.org/pdf/2501.05302 https://arxiv.org/pdf/2501.05302
deleted 16d ago
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cjbgkagh 16d ago
Probably be easier and more reliable to use star navigation with modern cameras, computers and atomic clocks. Especially for commercial aircraft flying above the weather.
- mike_d 16d ago
  Celestial navigation requires an accurate clock and an almanac that needs to be updated. It is completely impractical for non-military applications.
  - malfist 16d ago
    Does the almanac need updating? I regularly use plate solving with my telescope and I've never had to update it's stars database
  - raron 16d ago
    Is that really that impractical? 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.
    - 3eb7988a1663 16d ago
      They did it in the 60s for the B2 bomber[0]. I think computers are slightly faster and more reliable today, so it at least seems plausible. [0] https://www.righto.com/2026/04/B-52-star-tracker-angle-computer.html https://www.righto.com/2026/04/B-52-star-tracker-angle-compu...
m463 16d ago
maybe we need to update those giant concrete arrows on the ground... https://en.wikipedia.org/wiki/Transcontinental_Airway_System https://en.wikipedia.org/wiki/Transcontinental_Airway_System and have giant concrete QR codes
- dotancohen 15d ago
  You're not far off with the QR codes. Some military hardware actually match camera input to known maps to navigate. Mostly unmanned, one-way hardware.
numpad0 16d ago
Most pre-GPS navigation systems have shorter baselines than GPS and therefore accuracy is much worse, on top of generally being more complicated
civvv 16d ago
Guess its back to the good ol' map, compass and stopwatch.
torginus 16d ago
What about terrain following? I would guess decent topographical maps of the world aren't that hard to come by today, to get a good idea of where you are. 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.
- KeplerBoy 16d ago
  Entirely possible and poor visibility is not an issue if you have radar.
- atoav 16d ago
  My guess would be that the best solution is multi sensorial anyways. So you have GPS, but then you would have an Inertial Measurement Unit, based purely on acceleration and inertia, radar and barometric systems and maybe optical systems for terrain identification and celestial navigation. I have recently heard an episode of Amp Hour podcast¹ where they talked about using Bluetooth from satellites as a GPS replacement for asset tags. So maybe alternatives to GPS on different bands are on the verge. Another interesting idea would be to have an antenna array on the plane that captures different radio sources and the angles from which they seem to come from and create a always updating radio activity map that maps a certain "radio landscape" to a position on the planet. AFAIK this is currently being worked on as well under the name "radio-SLAM" (with SLAM standing for Simultaneous Localization and Mapping). This means, jammers could maybe even be used as potential beacons themselves. ¹: The episode in question: https://theamphour.com/728-space-age-bluetooth-with-alex-haro/ https://theamphour.com/728-space-age-bluetooth-with-alex-har...
mzi 15d ago
A bunch of us old salty sailing nerds were actually discussing Decca Navigator System¹ the other day that was still very present in the 90s on the ships we were sailing. Now all replaced and removed. https://en.wikipedia.org/wiki/Decca_Navigator_System https://en.wikipedia.org/wiki/Decca_Navigator_System
- myself248 15d ago
  Oh, wow! That seems to fill a gap below LORAN's range, and far exceeding its accuracy. I never heard of it before!
KaiserPro 15d ago
Sorry but this sounds like nostalgia. loran-c was prone to error. Yes, we can stop that with modern tech, but the problem with loran-c is you had location ambiguities. Decca was worse, unless you had a good initial fix, you were all sorts of fucked. There are of course modern alternatives, but they are not block proof, or turned on. There is a very good reason why GPS was opened up, because the alternatives were not anywhere near as good. Now, what are the alternatives? well hyperbolic navigation is still a thing, and with modern electronics you can get a pretty good fix without any of the nasty ambiguaty that loran-c had. If you are flying over land, then visual odometry is now at a point where you can locate pretty accurately autonomously (assuming cloud cover is your firend) Small low power ceasium clocks are $4k now, and only really need a few hundred millitwatts to run, which opens up a whole load of other ways to navigate. then there are IMUs, they are dirt cheap and way more accurate than 20 years ago. A calibrated array should be able to sustain reasonable accuracy after 30 minutes now
andix 15d ago
Are there modern positioning systems that can automatically join all those data sources into one position? Traditionally navaids are treated as completely separate sources and are shown on different kind of instruments. But they could also be used as a replacement source for GNSS data on a modern map screen. Depending on their kind they might not return a specific position, but in combination with other sources they often do via triangulation. PS: INS (Inertial Navigation) also still exits. It often works for quite a long time really precisely. Also precision can be calculated. So it can start as a dot on a map which becomes a bigger circle as the precision decreases. It could be automatically recalibrated whenever high confidence positioning is available.
- bronco21016 15d ago
  Yes, modern flight management computers in commercial airliners do exactly this. I can't speak to smaller aircraft. Essentially a position is calculated from VOR/DME, GPS, and INS. When there is disagreement it is flagged and procedures are in place to fall back. The issue is VOR/DME is slowly being decommissioned eliminating one of those sanity checks. It hasn't been degraded to the point of creating massive gaps in coverage over land but it will slowly happen if the rate of decommissioning continues. Ultimately, INS is sufficient for enroute navigation but if you're degraded to just that state, the impacts to traffic separation, particularly in congested airspace, are significant. Required Navigation Performance (RNP) levels dictate all of this.

buildsjets 16d ago

VOR is extremely short range and requires an extraordinary number of transmitters to provide any volume of coverage. Additionally it cannot provide coverage over oceanic areas. We USED TO have a nearly global long-range land based navigation system called LORAN, which only required one master station and a few remote stations to provide continent-scale coverage. But it was decommissioned in a cost savings move after it was determined that it could be replaced by GPS. It worked perfectly fine until it was decommissioned in 2010, not that long ago. 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. https://en.wikipedia.org/wiki/Loran-C https://en.wikipedia.org/wiki/Loran-C

verelo 16d ago
On VOR: It's also a PITA to use, and for inexperienced people, or someone who rarely uses it, they can confuse flying towards and away from the station.
- buildsjets 16d ago
  If you are a general aviation goober like me, flying a 1960's propeller airplane, sure, that is true. 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.
  - verelo 16d ago
    Yeah that makes sense. My experience is mostly in 70s to early 90's prop planes, I have had the opportunity to use a glass cockpit a few times and it was much easier. I guess i did the typical thing and contextualized this on my experiences and ignored that 99.9% of flights are not GA haha.
- _moof 16d ago
  Time was, if you didn't understand how to use VORs, you couldn't really fly. We used them as primary en route nav, as well as for approaches, for many decades. As a CFI I think most of the confusion around VORs these days comes down to poor or inadequate training.
  - ExoticPearTree 15d ago
    > As a CFI I think most of the confusion around VORs these days comes down to poor or inadequate training. I would say it is partially true. The reason I have trouble with VORs is that the equipment inside the plane is very awkward to use. The fact that the plane is in the center of the VOR display is super confusing as it shows everything in reverse: if the line is on the left it means the plane is on the right. And having to learn Morse Code to validate you tuned in the right frequency. And so on. I get it that when they invented that we did not have technology, but now we do and nothing is stopping us from using a digital display that can translate VORs/DMEs/NDBs fixes into GPS like routes. And knowing where every VOR is can make the map accurate too. That would make it very easy for a lot of people to use and not have to learn the arcane ways of how people used to fly 50 years ago. I don't need to know that I'm flying TO or FROM the station.
  - verelo 16d ago
    That's fair. I replied to someone else with a similar remark, but essentially doing most of my flying in 70s to 90s prop planes, I imagine the tools I'm most used to are just dated. Your point around training is likely very accurate, I had some great teachers but I also had a few instances of being given inaccurate information and having to teach the teacher so to speak.
    - Charon77 16d ago
      I don't fly and I wouldn't call my self someone that plays a lot of flight simulator. But I do enjoy navigation methods and I did learn the basics and practices of VOR navigation. I got an Android app that simulates flying courses, holding patterns etc, but only the navigation part. I would say I learned some intuition to it.
    - 15d ago
mschuster91 16d ago
> Additionally it cannot provide coverage over oceanic areas. 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.
- _moof 16d ago
  > sustaining human life Not really. Drone ships are very much a thing these days.
  - vanviegen 16d ago
    How can a drone ship hold its designated position while it's blocking gps?
    - Intermernet 16d ago
      Astral navigation is probably accurate enough
      - K0balt 15d ago
        Dead reckoning with a minute or two to get a gps fix with the jammer off once a day.
        Peanuts99 15d ago
        What's to stop someone spoofing a GPS signal during that fix?
        K0balt 15d ago
        Nothing, and if it were subtle enough it could be effective at making it drift around. Lots of ways to get a rough fix though, and you don’t need very good absolute accuracy offshore, using a compass and log to DR your way around. Even better if you have a wind vane and anemometer. The majority of your drift will be wind driven.
amelius 15d ago
Was LORAN also resistant against jamming/hacking?
- Thorondor 15d ago
  Nothing is completely foolproof, but LORAN is much, much more resistant to jamming than GPS. GPS satellites orbit over 20,000 km from Earth and transmit at very limited power (less than 50 W). That makes it easy to overpower their faint signals. On top of that, GPS operates at a frequency over 1 GHz which means you can broadcast a jamming signal with a small antenna. LORAN is the opposite. It uses low frequency, extremely high power signals transmitted from stations relatively closer to the receiver. Those design choices make it less precise but vastly more robust.

jacquesm 16d ago

And LORAN. But it may make a come-back. GPS signals are just incredibly weak so it takes next to nothing to drown them out, easier still if you are above the receiver.

toomuchtodo 16d ago
I would be curious on and interested in guidance from a GNSS expert on what the risk profile is when you're using jam resistant frequencies with a multi GNSS constellation chipset (GPS, Galileo, BeiDou), WAAS (GNSS corrections received via satellite), and when close enough to airports that support it, LAAS (GNSS corrections broadcast from airports). Follow up questions would be what countermeasures are available to bolster GNSS reliability during critical phases of flight (takeoff and landing), as well as how cellular tower networks could be used as distributed sensor fabrics for constantly monitoring for and triangulate GNSS jamming using SDR (or perhaps start with a handful of GNSS reference monitoring stations at major airports for this monitoring). https://news.ycombinator.com/item?id=49186101 https://news.ycombinator.com/item?id=49186101 https://news.ycombinator.com/item?id=49184484 https://news.ycombinator.com/item?id=49184484 GPSJam: Daily maps of possible GPS interference - https://news.ycombinator.com/item?id=37868106 https://news.ycombinator.com/item?id=37868106 - October 2023 (89 comments) GPSJam: Daily Maps of GPS Interference - https://news.ycombinator.com/item?id=32245346 https://news.ycombinator.com/item?id=32245346 - July 2022 (82 comments) https://en.wikipedia.org/wiki/Transmitter_hunting https://en.wikipedia.org/wiki/Transmitter_hunting | https://en.wikipedia.org/wiki/Pseudo-range_multilateration https://en.wikipedia.org/wiki/Pseudo-range_multilateration | https://www.arrl.org/direction-finding https://www.arrl.org/direction-finding https://geodesy.noaa.gov/CORS/ https://geodesy.noaa.gov/CORS/ | https://arcg.is/18fWq8 https://arcg.is/18fWq8
- leonidasrup 16d ago
  Because GPS and other GNSS have only a very weak signal strength there are no jam resistant frequencies, you can jam them all very efficiently, or you can jam them very efficiently in selective way (jam BeiDou, but not GPS). 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.scientificamerican.com/article/gps-and-the-world-s-first-space-war/ https://web.archive.org/web/20160208233555/http://www.scient...

jshier 16d ago

Seems like we'd need a modern version that's less susceptible to jamming, otherwise aren't we just replacing one jammable service with another?

michaelt 16d ago
There are two types of GPS jamming. 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.
- bb88 16d ago
  GPS jamming was being investigated by the NTSB as a possible reason for this air crash that killed 4 people near White Sands Missile Range. 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-crash-gps-jamming-22466131.html https://www.stripes.com/theaters/us/2026-08-05/ntsb-medevac-...
  - sokoloff 16d ago
    I’d bet a lot of money that the NTSB will determine that the pilots’ failure to maintain clearance from terrain during a visual approach will be the primary cause with contributing factors of dark, moonless night and GPS jamming. That one’s going to be on the flight crew, not the GPS jamming test. HN discussion: https://news.ycombinator.com/item?id=49181099 https://news.ycombinator.com/item?id=49181099
    - bb88 16d ago
      I'm not going to argue that as it's always easy to blame dead people, but there's two different types of jamming. 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.

sokoloff 16d ago

All VORs provide a radial that you’re on. Not all provide a distance to the station. VOR/DME or VORTACs provide both. Plain VORs do not. 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.

flewbee 16d ago
By taking a bearing from TWO VORs simultaneously, the distance to each can be computed. That's why planes have two VOR receivers and instruments.
- sokoloff 15d ago
  Two VOR stations will give you a fix, but since GPS took over from legacy RNAV, that’s now rarely used operationally in the US. More common is to use Nav2 tuned to a VOR to find an intersection on the arrival and Nav 1 to fly the final (ILS/LOC/VOR).

himata4113 16d ago

We have starlink I am sure they can figure something out.

mschuster91 16d ago
Starlink lacks the high precision atomic clocks on board of the satellites, that is also why Starlink needs a GPS fix to bootstrap itself.
- nomel 16d ago
  Maybe the starlink clocks could continuously calibrate from gps? Clock drift is usually a slow thing (like thermals). Their inter-satellite data links have all sorts of relative clocking info.
  - numpad0 16d ago
    IIUC, GPS picks one satellite and 3 more to establish time differences between the first one and the other 3. There's only one point in universe where the set of differences would match what was observed, given the broadcast orbital data of satellites, and that gives the location of the receiver. It's like you are provided radii and center coordinates of 3 circles on a paper that intersect at 1 point and you are to math that point. 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.
    - nomel 16d ago
      Coherency is a state. My question is if that state can be achieved by just tuning the individual clocks/locations based on GPS as a master. And, there's other tricks, with all the inter-satellite communication [1]. 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. [1] https://arxiv.org/pdf/2501.05302 https://arxiv.org/pdf/2501.05302

deleted 16d ago

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cjbgkagh 16d ago

Probably be easier and more reliable to use star navigation with modern cameras, computers and atomic clocks. Especially for commercial aircraft flying above the weather.

mike_d 16d ago
Celestial navigation requires an accurate clock and an almanac that needs to be updated. It is completely impractical for non-military applications.
- malfist 16d ago
  Does the almanac need updating? I regularly use plate solving with my telescope and I've never had to update it's stars database
- raron 16d ago
  Is that really that impractical? 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.
  - 3eb7988a1663 16d ago
    They did it in the 60s for the B2 bomber[0]. I think computers are slightly faster and more reliable today, so it at least seems plausible. [0] https://www.righto.com/2026/04/B-52-star-tracker-angle-computer.html https://www.righto.com/2026/04/B-52-star-tracker-angle-compu...

m463 16d ago

maybe we need to update those giant concrete arrows on the ground... https://en.wikipedia.org/wiki/Transcontinental_Airway_System https://en.wikipedia.org/wiki/Transcontinental_Airway_System and have giant concrete QR codes

dotancohen 15d ago
You're not far off with the QR codes. Some military hardware actually match camera input to known maps to navigate. Mostly unmanned, one-way hardware.

numpad0 16d ago

Most pre-GPS navigation systems have shorter baselines than GPS and therefore accuracy is much worse, on top of generally being more complicated

civvv 16d ago

Guess its back to the good ol' map, compass and stopwatch.

torginus 16d ago

What about terrain following? I would guess decent topographical maps of the world aren't that hard to come by today, to get a good idea of where you are. 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.

KeplerBoy 16d ago
Entirely possible and poor visibility is not an issue if you have radar.
atoav 16d ago
My guess would be that the best solution is multi sensorial anyways. So you have GPS, but then you would have an Inertial Measurement Unit, based purely on acceleration and inertia, radar and barometric systems and maybe optical systems for terrain identification and celestial navigation. I have recently heard an episode of Amp Hour podcast¹ where they talked about using Bluetooth from satellites as a GPS replacement for asset tags. So maybe alternatives to GPS on different bands are on the verge. Another interesting idea would be to have an antenna array on the plane that captures different radio sources and the angles from which they seem to come from and create a always updating radio activity map that maps a certain "radio landscape" to a position on the planet. AFAIK this is currently being worked on as well under the name "radio-SLAM" (with SLAM standing for Simultaneous Localization and Mapping). This means, jammers could maybe even be used as potential beacons themselves. ¹: The episode in question: https://theamphour.com/728-space-age-bluetooth-with-alex-haro/ https://theamphour.com/728-space-age-bluetooth-with-alex-har...

mzi 15d ago

A bunch of us old salty sailing nerds were actually discussing Decca Navigator System¹ the other day that was still very present in the 90s on the ships we were sailing. Now all replaced and removed. https://en.wikipedia.org/wiki/Decca_Navigator_System https://en.wikipedia.org/wiki/Decca_Navigator_System

myself248 15d ago
Oh, wow! That seems to fill a gap below LORAN's range, and far exceeding its accuracy. I never heard of it before!

KaiserPro 15d ago

Sorry but this sounds like nostalgia. loran-c was prone to error. Yes, we can stop that with modern tech, but the problem with loran-c is you had location ambiguities. Decca was worse, unless you had a good initial fix, you were all sorts of fucked. There are of course modern alternatives, but they are not block proof, or turned on. There is a very good reason why GPS was opened up, because the alternatives were not anywhere near as good. Now, what are the alternatives? well hyperbolic navigation is still a thing, and with modern electronics you can get a pretty good fix without any of the nasty ambiguaty that loran-c had. If you are flying over land, then visual odometry is now at a point where you can locate pretty accurately autonomously (assuming cloud cover is your firend) Small low power ceasium clocks are $4k now, and only really need a few hundred millitwatts to run, which opens up a whole load of other ways to navigate. then there are IMUs, they are dirt cheap and way more accurate than 20 years ago. A calibrated array should be able to sustain reasonable accuracy after 30 minutes now

andix 15d ago

Are there modern positioning systems that can automatically join all those data sources into one position? Traditionally navaids are treated as completely separate sources and are shown on different kind of instruments. But they could also be used as a replacement source for GNSS data on a modern map screen. Depending on their kind they might not return a specific position, but in combination with other sources they often do via triangulation. PS: INS (Inertial Navigation) also still exits. It often works for quite a long time really precisely. Also precision can be calculated. So it can start as a dot on a map which becomes a bigger circle as the precision decreases. It could be automatically recalibrated whenever high confidence positioning is available.

bronco21016 15d ago
Yes, modern flight management computers in commercial airliners do exactly this. I can't speak to smaller aircraft. Essentially a position is calculated from VOR/DME, GPS, and INS. When there is disagreement it is flagged and procedures are in place to fall back. The issue is VOR/DME is slowly being decommissioned eliminating one of those sanity checks. It hasn't been degraded to the point of creating massive gaps in coverage over land but it will slowly happen if the rate of decommissioning continues. Ultimately, INS is sufficient for enroute navigation but if you're degraded to just that state, the impacts to traffic separation, particularly in congested airspace, are significant. Required Navigation Performance (RNP) levels dictate all of this.