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China's version of GPS now has more satellites than US original

asia.nikkei.com

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Re: China's version of GPS now has more satellites than US original

#61

Post by lolc »

michaelt wrote: post #22
lolc wrote: post #7

> 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.

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 differ…

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.

Re: China's version of GPS now has more satellites than US original

#62

Post by xbmcuser »

867-5309 wrote: post #56
xbmcuser wrote: post #20

Earlier quoted context omitted.

I don't get something you have satellites of glonass, gps and beidou what's stopping anyone from getting better accuracy using all 3 at the same time.

because they are independent systems; they cannot communicate triangulation data between themselves

Isn't the triangulation being done on the phone/device GPS chip ? The same chip is doing it for all 3 services. The chip gets the data of the satellite positions and then shows its location in relation to them that how I thought gps/other systems worked.

Re: China's version of GPS now has more satellites than US original

#63

Post by dx034 »

raihansaputra wrote: post #48
credit_guy wrote: post #38

So, if North Korea wants to develop an ICBM, the main challenges are 4: take off (which they appear to have mastered), miniaturization of the bomb, navigation and reentry vehicle. All the remaining 3 are quite difficult, and navigation in particular was traditionally done by a mix of inertial (i.e. based on gyroscopes) and celestial (i.e. based on the observation of stars). GPS makes all this unnecessary. If NK uses…

The unencrypted GPS automatically disables themselves when they detect speeds of a missile to prevent exactly this.

You cannot disable single receivers, they could only shut down or encrypt the whole system (at least for part of the world). Which could be standard procedure if they detect an incoming attack. With 3 other systems also available, that probably won't have much of an effect.

Re: China's version of GPS now has more satellites than US original

#64

Post by dx034 »

GaurVimen wrote: post #11

TL;DR at bottom. While impressive, "how many satellites you can see over a major city" is not an accurate way to judge a GPS satellite network. To understand why, you have to understand how GPS works. Basically, each GPS has a super accurate clock on board. These are all synced up. These satellites transmit a signal regularly on predetermined schedules. Your phone or car or whatever else is using GPS listens for thes…

Both in cities and mountains you'll often not have 180° visibility. Having more satellites available increases the chances to always have 4 in sight.

Re: China's version of GPS now has more satellites than US original

#65

Post by jaimex2 »

onethought wrote: post #47
jaimex2 wrote: post #27

Welcome to 1978 China.

This reminds me of the arrogance of the British Empire... Does the US (govt/people/blob) really not see the writing on the wall with this?

Am I the only one not impressed with China copying 40 year old milestones? Surely...

Re: China's version of GPS now has more satellites than US original

#66

Post by not_a_cop75 »

gandalfian wrote: post #26
Maakuth wrote: post #19

Isn't the proliferation of multiple GNSS constellations actually quite positive thing? The smartphone geolocation chips seem to have no problem receiving signals from all constellations. So effectively this competition between the systems allows for denser coverage of location satellites. This in turn should enable more accuracy and faster location acquisition even with limited sky visibility. In security sense, it s…

Everyone sharing one system is excellent. Everyone sharing four increasingly redundant systems starts to look like a waste of money. We need a carpooling equivalent gps system. Still better than more bombs I guess.

If everyone is thinking the same thing, then someone isn't thinking. (This time, I wasn't thinking, but I agree with the sentiment.)

Re: China's version of GPS now has more satellites than US original

#67

Post by vinay427 »

Spare_account wrote: post #46
vinay427 wrote: post #36

Earlier quoted context omitted.

Newer GPS satellites apparently don't support selective availability, so they would have no way of preventing access to only civilian devices. Of course, any of these systems can be jammed or shot down but that would affect anyone using it. > In September 2007, the U.S. government announced its decision to procure the future generation of GPS satellites, known as GPS III, without the SA feature. Doing this will make…

If I wanted my neighbours to trust my GPS system more, I'd tell them I don't have selective availability.

Sure. If you wanted GPS to be more widely used and depended on with no ulterior motives, you would also tell them you don't have selective availability. All of these systems require trusting the operators at the end of the day, and I'm not making the claim that one should depend on any single system.

Re: China's version of GPS now has more satellites than US original

#68

Post by vinay427 »

dragonelite wrote: post #44
vinay427 wrote: post #36

Earlier quoted context omitted.

Newer GPS satellites apparently don't support selective availability, so they would have no way of preventing access to only civilian devices. Of course, any of these systems can be jammed or shot down but that would affect anyone using it. > In September 2007, the U.S. government announced its decision to procure the future generation of GPS satellites, known as GPS III, without the SA feature. Doing this will make…

Why would a reformist country like China and Russia trust such a thing. We were also told that mass surveillance was a conspiracy/nutjob story, but the Snowden leaks has shown us a different world.

They wouldn't, and I can see why. I was just adding some information. As far as anyone in the public has been told, both GPS and Galileo will remain open for anyone to use, but depending on that requires trusting whoever runs it.

Re: China's version of GPS now has more satellites than US original

#69

Post by bgee »

Saw some comments on how countries should collaborate instead of building 4 different GNSS, well China definitely tried:

> The Chinese feel that they were badly used and partly humiliated by Europe. They were brought into the Galileo consortium as partners, and they paid the EU for the privilege, only to see themselves shut out of Galileo’s controlling bodies...China would have had less influence over Galileo than Japan and India have over GPS, and those two nations have not paid the US a single dime for their cooperation in the signal augmentation systems they are now building [0].

[0]: http://www.thespacereview.com/article/1307/1

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