7 ms·

The race to find GPS alternatives

32 points by Brajeshwar 1y ago

infocollector 1y ago
The problem I see with investing in such technologies: 1. Satellites are too far to fight anything on ground (Power per unit area (i.e., intensity) decreases as the square of the distance) 2. If the Satellites are relaying to things on the ground, they are also relaying their location (easy adversarial targets) 3. In a war (they mention Ukraine in the article), first thing that is toast is these satellites. I don't think this is the right replacement for GPS. Perhaps someone here can correct me if I am wrong?
- dieselerator 1y ago
  > I don't think this is the right replacement for GPS. Perhaps someone here can correct me if I am wrong? Though I do not agree with your reasons, I do think this Xona is not the right replacement for GPS.
- icegreentea2 1y ago
  It's probably worth considering the military and non-military uses separately. The USG military uses is attractive not as a replacement of GPS, but as a supplement/complement. If they could truly manage to use the same receivers, then this provides an extra layer of redundancy. There are 32 GPS satellites in the current constellation. Being in MEO means you need pretty beefy ASAT to take it take them down, but we could assume that China could pull it off. Xona's constellation would add redundancy (splashing 258 is just a lot more targets). For non USG uses, I imagine Xona is making two different pitches. a) You can achieve GPS+RTK level accuracy without needing RTK base stations. b) Increased jamming/spoofing resiliency, intended for short of war (aka hybrid war/grey zone) situations. For example, I imagine Xona will attempt to setup a private encrypted signal which they'll sell to friendly/allied nation airliners and similar industries.
SoftTalker 1y ago
How good are accelerometers these days? With a known starting point, map data, a good clock, and accelerometers you should be able to compute your position using dead reckoning.
- monster_truck 1y ago
  Anything that works well enough to do this usefully & reliably is export controlled for obvious reasons
- userbinator 1y ago
  https://en.wikipedia.org/wiki/Inertial_navigation_system#Drift_rate https://en.wikipedia.org/wiki/Inertial_navigation_system#Dri... not that great although they've been in use for many decades.
- vrighter 1y ago
  They already do this, as a fallback to when gps fails. It's not accurate enough for long distances.
- rcxdude 1y ago
  Only good for a limited time, is the main thing. Your error increases quadratically with time, so even a really good IMU will drift dramatically at some point without some kind of periodic position fix.
asdefghyk 1y ago
How did ships navigate 200 years ago? Not sure how accurate it was ? How about using the stars? ... only at night ? Use triangulation to known RF transmissions ( ie like direction finding of RF signals ) Geography recognition , rivers mountain's . towns etc ( Lidar ? ) Broadcast this info on some other secret frequency - drones only need to listen to the info Use radar to track drone and broadcast its position to the item ...
- mshook 1y ago
  The B-52 and SR-71 had star tracking systems for that exact reason. Not sure about the B-52 version but the SR-71 worked in daylight. https://www.glennsmuseum.com/items/b52_astro/ https://www.glennsmuseum.com/items/b52_astro/ https://theaviationgeekclub-com.cdn.ampproject.org/v/s/theaviationgeekclub.com/the-sr-71-astroinertial-navigation-system-aka-r2-d2-was-crucial-in-blackbird-mission-heres-why https://theaviationgeekclub-com.cdn.ampproject.org/v/s/theav...
  - sroussey 1y ago
    I wonder how satellites affect that now. So many more by an orders of magnitude
    - nullc 1y ago
      They don't. Cloud cover, OTOH, is a real killer-- but not a problem for high altitude aircraft.
- mycall 1y ago
  I wonder if weather balloons could be cheaply outfitted with star tracking and relay its position back down as a temporary GPS-like backup system.
politelemon 1y ago
Question please, it says that jamming these is more difficult. But doesn't that mean it's not impossible, so at some point in the future it could happen?
- icegreentea2 1y ago
  Yeah, these are jammable on day 1 - they're just more difficult to jam, so you need make your jammers either more powerful or closer to the target. The cost and scale of disruption matters.
- Frieren 1y ago
  > it's not impossible That is true for almost all security. It is not impossible to break cryptography, but it is costly enough as to not be viable in most cases. Most of security is about to make it costly enough to break as to not be worth it.
  - thesnide 1y ago
    as the saying goes, one doesnt need to outrun the hungry bear. one just need to outrun the other fellow that serve as bait...
  - cykros 1y ago
    One time pad cryptography generated with truly random pads with no reuse of keys and no leaks in key transmission being the big exception. But yea, calling it inconvenient for most uses is quite an understatement. It did serve many spies well though during the Cold War using numbers stations, even if the Soviets were known to take short cuts by just having a room full of people randomly hitting keyboards rather than using true randomness.
- solsane 1y ago
  Yes. Jamming is just introducing noise that drowns out our signal. E.g. reduces the signal to noise ratio.
AlotOfReading 1y ago
I really don't understand the founding motivation for this company. For one, autonomous vehicles (e.g. Waymo) don't use GNSS as the primary means of localization. You can also achieve centimeter (and higher) precision with RTK. The main source of errors is usually reflections, which are still a problem here. A higher SNR helps, but I'm not sure it helps enough to justify the endeavor.
nimish 1y ago
https://en.wikipedia.org/wiki/Pulsar-based_navigation https://en.wikipedia.org/wiki/Pulsar-based_navigation is a fun one, if not that practical
bob1029 1y ago
I think broadcast positioning system could be an interesting path. https://www.jeffgeerling.com/blog/2025/bps-gps-alternative-nobodys-heard https://www.jeffgeerling.com/blog/2025/bps-gps-alternative-n... Discussed 2 months ago: https://news.ycombinator.com/item?id=43669308 https://news.ycombinator.com/item?id=43669308
eqvinox 1y ago
"… approximately a hundred times stronger than the GPS signal … That means the reach of jammers will be much smaller against our system …" This assumes the jammer stays at the same power output, no? Why wouldn't adversaries just build stronger jammers?

32 points by Brajeshwar 1y ago

The problem I see with investing in such technologies: 1. Satellites are too far to fight anything on ground (Power per unit area (i.e., intensity) decreases as the square of the distance) 2. If the Satellites are relaying to things on the ground, they are also relaying their location (easy adversarial targets) 3. In a war (they mention Ukraine in the article), first thing that is toast is these satellites. I don't think this is the right replacement for GPS. Perhaps someone here can correct me if I am wrong?

dieselerator 1y ago
> I don't think this is the right replacement for GPS. Perhaps someone here can correct me if I am wrong? Though I do not agree with your reasons, I do think this Xona is not the right replacement for GPS.
icegreentea2 1y ago
It's probably worth considering the military and non-military uses separately. The USG military uses is attractive not as a replacement of GPS, but as a supplement/complement. If they could truly manage to use the same receivers, then this provides an extra layer of redundancy. There are 32 GPS satellites in the current constellation. Being in MEO means you need pretty beefy ASAT to take it take them down, but we could assume that China could pull it off. Xona's constellation would add redundancy (splashing 258 is just a lot more targets). For non USG uses, I imagine Xona is making two different pitches. a) You can achieve GPS+RTK level accuracy without needing RTK base stations. b) Increased jamming/spoofing resiliency, intended for short of war (aka hybrid war/grey zone) situations. For example, I imagine Xona will attempt to setup a private encrypted signal which they'll sell to friendly/allied nation airliners and similar industries.

SoftTalker 1y ago

How good are accelerometers these days? With a known starting point, map data, a good clock, and accelerometers you should be able to compute your position using dead reckoning.

monster_truck 1y ago
Anything that works well enough to do this usefully & reliably is export controlled for obvious reasons
userbinator 1y ago
https://en.wikipedia.org/wiki/Inertial_navigation_system#Drift_rate https://en.wikipedia.org/wiki/Inertial_navigation_system#Dri... not that great although they've been in use for many decades.
vrighter 1y ago
They already do this, as a fallback to when gps fails. It's not accurate enough for long distances.
rcxdude 1y ago
Only good for a limited time, is the main thing. Your error increases quadratically with time, so even a really good IMU will drift dramatically at some point without some kind of periodic position fix.

asdefghyk 1y ago

How did ships navigate 200 years ago? Not sure how accurate it was ? How about using the stars? ... only at night ? Use triangulation to known RF transmissions ( ie like direction finding of RF signals ) Geography recognition , rivers mountain's . towns etc ( Lidar ? ) Broadcast this info on some other secret frequency - drones only need to listen to the info Use radar to track drone and broadcast its position to the item ...

mshook 1y ago
The B-52 and SR-71 had star tracking systems for that exact reason. Not sure about the B-52 version but the SR-71 worked in daylight. https://www.glennsmuseum.com/items/b52_astro/ https://www.glennsmuseum.com/items/b52_astro/ https://theaviationgeekclub-com.cdn.ampproject.org/v/s/theaviationgeekclub.com/the-sr-71-astroinertial-navigation-system-aka-r2-d2-was-crucial-in-blackbird-mission-heres-why https://theaviationgeekclub-com.cdn.ampproject.org/v/s/theav...
- sroussey 1y ago
  I wonder how satellites affect that now. So many more by an orders of magnitude
  - nullc 1y ago
    They don't. Cloud cover, OTOH, is a real killer-- but not a problem for high altitude aircraft.
mycall 1y ago
I wonder if weather balloons could be cheaply outfitted with star tracking and relay its position back down as a temporary GPS-like backup system.

politelemon 1y ago

Question please, it says that jamming these is more difficult. But doesn't that mean it's not impossible, so at some point in the future it could happen?

icegreentea2 1y ago
Yeah, these are jammable on day 1 - they're just more difficult to jam, so you need make your jammers either more powerful or closer to the target. The cost and scale of disruption matters.
Frieren 1y ago
> it's not impossible That is true for almost all security. It is not impossible to break cryptography, but it is costly enough as to not be viable in most cases. Most of security is about to make it costly enough to break as to not be worth it.
- thesnide 1y ago
  as the saying goes, one doesnt need to outrun the hungry bear. one just need to outrun the other fellow that serve as bait...
- cykros 1y ago
  One time pad cryptography generated with truly random pads with no reuse of keys and no leaks in key transmission being the big exception. But yea, calling it inconvenient for most uses is quite an understatement. It did serve many spies well though during the Cold War using numbers stations, even if the Soviets were known to take short cuts by just having a room full of people randomly hitting keyboards rather than using true randomness.
solsane 1y ago
Yes. Jamming is just introducing noise that drowns out our signal. E.g. reduces the signal to noise ratio.

AlotOfReading 1y ago

I really don't understand the founding motivation for this company. For one, autonomous vehicles (e.g. Waymo) don't use GNSS as the primary means of localization. You can also achieve centimeter (and higher) precision with RTK. The main source of errors is usually reflections, which are still a problem here. A higher SNR helps, but I'm not sure it helps enough to justify the endeavor.

nimish 1y ago

https://en.wikipedia.org/wiki/Pulsar-based_navigation https://en.wikipedia.org/wiki/Pulsar-based_navigation is a fun one, if not that practical

bob1029 1y ago

I think broadcast positioning system could be an interesting path. https://www.jeffgeerling.com/blog/2025/bps-gps-alternative-nobodys-heard https://www.jeffgeerling.com/blog/2025/bps-gps-alternative-n... Discussed 2 months ago: https://news.ycombinator.com/item?id=43669308 https://news.ycombinator.com/item?id=43669308

eqvinox 1y ago

"… approximately a hundred times stronger than the GPS signal … That means the reach of jammers will be much smaller against our system …" This assumes the jammer stays at the same power output, no? Why wouldn't adversaries just build stronger jammers?