5 ms·

> When using BeiDou for car navigation, the receiver could theoretically transmit the car's location to a satellite in orbit, said Dean Cheng, a senior research

by lolc 7y ago

> When using BeiDou for car navigation, the receiver could theoretically transmit the car's location to a satellite in orbit, said Dean Cheng, a senior research fellow at the Heritage Foundation in Washington. Details on this? What does "theoretically" mean? Are there known protocols for this? Implementations? A lot of things could "theoretically" be done but aren't in practice.

willis936 7y ago
This seems rather counter to what I know about GPS. It is a one way link.
mytailorisrich 7y ago
Seems that the experimental Beidou-1 worked that way, and that Galileo is also able to work that way [1]. However, this does not seem to be how the deployed version of Beidou works, and this does not seem required with Galileo either. I also note that Qualcomm produces Beidou receiver chips so these are under American control. Overall I have the feeling that the article is trying hard to whip up fears over Beidou... [1] https://space.stackexchange.com/questions/30839/is-two-way-communication-really-required-to-use-beidou-gnss https://space.stackexchange.com/questions/30839/is-two-way-c...
- lolc 7y ago
  I do wonder where this "scare" comes from. I remember a Bloomberg article that also posited Beidou as a danger. Sure these systems have military applications, but why not talk about those dangers directly instead of trying to portray civilian use as problematic?
y04nn 7y ago
I doubt this can be done with a standard "GPS" omnidirectional antenna. This would require a lot of power.
Gupie 7y ago
Might be referring to their proposed Search and Rescue features, SAR.
- tialaramex 7y ago
  COSPAS SARSAT rides along on new GNSS (GPS-like) birds from several nations because it's a good place to put it. They move in the sky (which means a beacon without its own ability to determine location can be triangulated using the doppler effect, not possible from a Geostationary communications satellite), there are lots of them, and they cover the whole Earth (the weather sats used for COSPAS SARSAT today are focused on areas where people care most about the weather, rather than aiming for global coverage...) The COSPAS SARSAT beacons run at a different frequency to GNSS, they emit bursts of digital data at 406 MHz when active, containing a unique ID for the beacon, optionally (if fitted) its own estimate of its location, and some other data. A global database maps unique IDs to owner/ operators and the nearest rescue agency will try to figure out if this is a genuine alert (e.g. phoning your emergency contact "Hi, is Gupie out on their yacht today? I see, and how many are with them?") and then deploy appropriate resources. Beacons are entirely passive until you activate them, and then you really want absolutely anybody to know where you are because you want rescuing. "Privacy" feels like a distant problem if you are currently in a leaking raft a hundred miles out to sea or just broke your leg half way up a mountain.
michaelt 7y ago
I suspect this is a misunderstanding on the part of Dean Cheng. Beidou-1 used a two-way link, because it used two satellites in the same orbit. This means the satellite can track all users. But Beidou-2 supports a one-way link - the same operating principle as GPS, GLONASS and Galileo - where the satellites can't track users. The downside to this design is it needs a lot more satellites, and they have to be in different orbits. Beidou-2 retains some backwards-compatibility with the two-way link, but if your cell phone's GPS chip supports Beidou, it'll be the one-way link. You'd notice the 20cm antenna and poor battery life if you had the two-way link!
- throw0101a 7y ago
  It should be noted that BeiDou-1 and -2 are/were regional systems. The BeiDou-3 currently being deployed is global.
- lolc 7y ago
  Interesting, thanks! I was wondering how two-way communication would work at scale. I often talk to people who are worried about being tracked and a recurring topic is the one-way property of GPS.

by lolc 7y ago

willis936 7y ago

This seems rather counter to what I know about GPS. It is a one way link.

mytailorisrich 7y ago

Seems that the experimental Beidou-1 worked that way, and that Galileo is also able to work that way [1]. However, this does not seem to be how the deployed version of Beidou works, and this does not seem required with Galileo either. I also note that Qualcomm produces Beidou receiver chips so these are under American control. Overall I have the feeling that the article is trying hard to whip up fears over Beidou... [1] https://space.stackexchange.com/questions/30839/is-two-way-communication-really-required-to-use-beidou-gnss https://space.stackexchange.com/questions/30839/is-two-way-c...

lolc 7y ago
I do wonder where this "scare" comes from. I remember a Bloomberg article that also posited Beidou as a danger. Sure these systems have military applications, but why not talk about those dangers directly instead of trying to portray civilian use as problematic?

y04nn 7y ago

I doubt this can be done with a standard "GPS" omnidirectional antenna. This would require a lot of power.

Gupie 7y ago

Might be referring to their proposed Search and Rescue features, SAR.

tialaramex 7y ago
COSPAS SARSAT rides along on new GNSS (GPS-like) birds from several nations because it's a good place to put it. They move in the sky (which means a beacon without its own ability to determine location can be triangulated using the doppler effect, not possible from a Geostationary communications satellite), there are lots of them, and they cover the whole Earth (the weather sats used for COSPAS SARSAT today are focused on areas where people care most about the weather, rather than aiming for global coverage...) The COSPAS SARSAT beacons run at a different frequency to GNSS, they emit bursts of digital data at 406 MHz when active, containing a unique ID for the beacon, optionally (if fitted) its own estimate of its location, and some other data. A global database maps unique IDs to owner/ operators and the nearest rescue agency will try to figure out if this is a genuine alert (e.g. phoning your emergency contact "Hi, is Gupie out on their yacht today? I see, and how many are with them?") and then deploy appropriate resources. Beacons are entirely passive until you activate them, and then you really want absolutely anybody to know where you are because you want rescuing. "Privacy" feels like a distant problem if you are currently in a leaking raft a hundred miles out to sea or just broke your leg half way up a mountain.

michaelt 7y ago

I suspect this is a misunderstanding on the part of Dean Cheng. Beidou-1 used a two-way link, because it used two satellites in the same orbit. This means the satellite can track all users. But Beidou-2 supports a one-way link - the same operating principle as GPS, GLONASS and Galileo - where the satellites can't track users. The downside to this design is it needs a lot more satellites, and they have to be in different orbits. Beidou-2 retains some backwards-compatibility with the two-way link, but if your cell phone's GPS chip supports Beidou, it'll be the one-way link. You'd notice the 20cm antenna and poor battery life if you had the two-way link!

throw0101a 7y ago
It should be noted that BeiDou-1 and -2 are/were regional systems. The BeiDou-3 currently being deployed is global.
lolc 7y ago
Interesting, thanks! I was wondering how two-way communication would work at scale. I often talk to people who are worried about being tracked and a recurring topic is the one-way property of GPS.