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China's version of GPS now has more satellites than US original
- aritmo 7y agoIs there any information about the accuracy of Beidu compared to Galileo?
- Gustomaximus 7y agoIn the article the say accuracy is coming down to 1m vs 3-5 for other GPS
- wolfgke 7y ago> In the article the say accuracy is coming down to 1m vs 3-5 for other GPS In which areas?
- stunt 7y ago> As of June 28, Chinese satellites were observed more frequently than GPS satellites in 130 of 195 countries (U.N. member states plus the Vatican and Palestine). More than 20 BeiDou satellites were observed over mainland China.
- xbmcuser 7y agoI 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.
- 867-5309 7y agobecause they are independent systems; they cannot communicate triangulation data between themselves
- xbmcuser 7y agoIsn'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.
- willis936 7y agoWith military receivers (or codeless phase tracking) the current constellation is good down to centimeters.
- londons_explore 7y agoThis isn't possible without third party data. Things like the refractive index of the atmosphere (which depends on weather patterns), and the fact orbits are slightly warped due to varying gravitational fields and radiation pressure from the sun, all add up to location innacuracies unless you can correct for these effects. That correction requires data, which needs to come from a third party because the satellites don't transmit it.
- willis936 7y agoCorrect, if only L1 is used. However as GPS exists today receivers can track phase variations between L1 and L2 without the codes necessary to decode the signal on L2.
- dragonelite 7y agoGroundbased gps transmitters might help to increase accuracy.
- PaulAJ 7y agoActually its a bit more sophisticated. Galileo ground stations measure their reported position against the actual, and then transmit correction data to the satellites which then retransmit it with the rest of the position data.
- flywithdolp 7y agoThe space race Seems like that's the next goal of the big nations. How can they have more control over the space
- 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 agoThis seems rather counter to what I know about GPS. It is a one way link.
- mytailorisrich 7y agoSeems 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 agoI 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 agoI doubt this can be done with a standard "GPS" omnidirectional antenna. This would require a lot of power.
- Gupie 7y agoMight be referring to their proposed Search and Rescue features, SAR.
- nullc 7y agoIt doesn't help that the GPS modernization project was delayed by a decade re-prioritization after 9/11. Though this result is also because BeiDou has intentionally uneven coverage via satellites with inclined orbits that result in much better coverage (and better signal angles, high off the horizon) in asia.
- GaurVimen 7y agoTL;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 these signals. Your device knows when exactly all the satellites sent their signal. It listens and counts how long it takes to receive each signal. With the length of time it takes to receive each signal from each satellite, it can pinpoint your location. For basic operations you require three satellites for an approximate location. For precise operations you need line of sight to four satellites, as the fourth enables you to calculate your altitude. At no point do you need more than 4 in sight. Why this is important is because the U.S. satellite constellation has 32 currently operating GPS satellites. In addition to those, we have 8 that are currently in space, ready to turn on, but they aren't because there's no reason to have them on. There's no doubt in my mind these satellites have additional secret reasons for being up there. That's the only reason they'd need that many. TL;DR:While they do have more active satellites, it's pointless for navigation purposes. Additionally, counting the backup satellites the U.S. Has operational but currently turned off in "standby" mode, we still have more. EDIT: Not everything I stated is completely accurate. See comments below for some clarifications. Make sure to upvote them if you found them helpful.
- huhtenberg 7y ago> At no point do you need more than 4 in sight. Unless you are measuring something with high precision over long periods of time. Like dam flexing or ground shifts. The more sats you have, the better you'll be at eliminating the signal noise (due to the ionosphere transition and what not). Also, regarding this - > "how many satellites you can see over a major city" is not an accurate way to judge a GPS satellite network. You are completely missing their point - you are in the _city_, a place with tall buildings that give you just a slice of the sky. So the more satellites you have above, the better you chances you will see _enough_ from where you are standing.
- mshook 7y ago
- huhtenberg 7y agoAt some point in mid-90s GLONASS had more satellites in orbit than GPS, so the sat count alone is not a terribly interesting metric.
- dragonsh 7y agoWouldn't it be nice instead of countries an open academic agency launch a series of open source satellites for locations. Hopefully likes of apple, Google, Microsoft, alibaba, benz, BMW, Toyota, Amazon, Qualcomm, European space agency can fund it. But I doubt it will happen as it's considered more strategic investment with military implications. But I am still hopeful like internet(which was designed for military purpose but now controlled by civilian authorities), locations can be free off selfish national interests.
- ksec 7y agoSomething SpaceX could consider? Given their ambition with Satellite Internet backbone.
- dragonsh 7y agoYeah hopefully there can be a consortium of Automobile manufacturers, internet companies and academia which can launch such a constellation of open source satellites for location services. Hopefully that can be combined with terrestrial peer to peer network to make sure it works even if military or specific nation wants to block it.
- raihansaputra 7y agoIATA would also be a suitable member. All civilian aircraft still rely on the unencrypted part of these GNSS systems AFAIK.
- yoz-y 7y agoI know nothing about satellites but couldn't the Starlink constellation be used for positioning in some way? It already has twice the amount of satellites and will have an order of magnitude more than any other current positioning system.
- PaulAJ 7y agoThis doesn't make sense. How can there be more satellites in the Eastern hemisphere than in the Western? Navigation satellites are in low earth orbit: they go around the earth every couple of hours. I could understand if one constellation had better polar coverage while another has better equatorial, but an east-west divide isn't physically possible (unless the Chinese are turning their satellites off when over the Americas).
- deleted 7y ago[deleted]
- sumanthvepa 7y agoIt's the dynamics of the the satellites' movement that create this effect. At any point in time it is possible for there to be more satellites in one region of the sky than elsewhere. That does not mean that any one satellite stays in the same position. The satellites continue to move around the planet.
- ZeKZ 7y agoThey use a lot of geosynchronous orbits over China to have a better coverage in this area. Take a look at the orbits here : https://www.researchgate.net/figure/Ground-tracks-of-the-BeiDou-satellites-and-distribution-of-the-experimental-tracking_fig1_236080831 https://www.researchgate.net/figure/Ground-tracks-of-the-Bei...
- robocat 7y agoEasily if using QZSS or synchronous orbits. For example the Japanese use QZSS orbits to for 3 of their satellites: https://en.m.wikipedia.org/wiki/Quasi-Zenith_Satellite_System https://en.m.wikipedia.org/wiki/Quasi-Zenith_Satellite_Syste...
- Maakuth 7y agoIsn'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 seems that the situation virtually rules out the possibility of selectively denying some party GNSS access. So if you want to make your adversary location-blind, you'll have to accept losing location data yourself, right?
- gandalfian 7y agoEveryone 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.
- kzrdude 7y agoWhat level of redundancy is needed? Having three global systems seems reasonable, if it's an important service.
- ddalex 7y agothe problem with just one is that US will insist having a deadswitch on it, just like it did with Galileo. so you must have your own if you don't want US to have a Damocles sword over you
- vinay427 7y agoNewer 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 the policy decision of 2000 permanent and eliminate a source of uncertainty in GPS performance that had been of concern to civil GPS users worldwide. https://www.gps.gov/systems/gps/modernization/sa/ https://www.gps.gov/systems/gps/modernization/sa/
- jaimex2 7y agoWelcome to 1978 China.
- onethought 7y agoThis 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?
- jaimex2 7y agoAm I the only one not impressed with China copying 40 year old milestones? Surely...
- throw0101a 7y agoGiven that BeiDou-3 MEO has a different orbital altitude (21500km) than GPS (20500km) and thus different orbital characteristics, wouldn't a different number of satellites be needed? I'm not sure that the number of satellites is that significant, and simply reflects design needs/constraints. Ran across a good lecture series on GNSS a while ago going into more detail than most people care about ("3.3 - From Keplerian parameters to Earth centered Earth fied ECEF frame"). Module 6.7 - BeiDou: * https://www.youtube.com/watch?v=Rpx1ySCKO3Q https://www.youtube.com/watch?v=Rpx1ySCKO3Q Playlist: * https://www.youtube.com/playlist?list=PLGvhNIiu1ubyEOJga50LJMzVXtbUq6CPo https://www.youtube.com/playlist?list=PLGvhNIiu1ubyEOJga50LJ...
- credit_guy 7y agoSo, 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 US GPS, there are most likely countermeasures in place, for example if the US detects an NK ICBM launch, then it stops or perturbs the GPS signal. New providers of GPS complicate this problem.
- onethought 7y agoIs this just conjecture? It seems ridiculous that the US would rely on the fact they can control GPS satellites as form of missile defence... So shooting down their GPS satellites would also hamper there ability to launch ICBMs? Seems equally unbelievable.
- credit_guy 7y agoIt's a conjecture indeed, as many defense things are classified, but you can bet good money it is true. > It seems ridiculous that the US would rely on the fact they can control GPS satellites as form of missile defense The US most certainly would not entirely rely on that. It would only be one tool in the toolbox. Nuclear ICBM attacks are so dangerous, that the defense by necessity uses a multi-pronged approach. It starts from diplomatic pressure, and technology export controls (see for example the Wassenaar arrangement [1] that lists the controls for inertial and celestial navigation in chapter 7. The limits on the GPS receivers exist as well, unfortunately I can't point you to the exact source). The actual physical defense options against a moving missile are listed in [2], such as the Ground Based Interceptors, the Aegis system and the THAAD system. It's all but certain that in case of credible intelligence of an imminent hostile ICBM launch, the US has pre-launch options as well (the current NK ICBM used liquid fuel, and the launch facilities are known and monitored; you will notice that one or two days before any NK missile test the press already writes articles about the likely launch). Considering all this, would the US neglect the possibility of altering the GPS signal in case it detects a hostile ICBM launch? For example, the reentry vehicle travels at many km/s. Early detonation by only half a second can reduce the impact of the bomb by a factor of 10 easily. If the missile has not GPS signal and only relies on less-than-state-of-the-art inertial and celestial navigation (which may be ok for horizontal coordinates, but not that great of altitude) that may make a huge difference. So my bet is not only that the US will promptly alter its GPS signal, but will have means to spoof the signal from the Russian and Chinese systems as well, and agreements in place with the European Galileo system too. However, as I said before, the problem is more complicated: the Russian and Chinese are not dumb, they most likely have their counter-counter-measures too. [1] https://www.wassenaar.org/app/uploads/2018/12/WA-DOC-18-PUB-001-Public-Docs-Vol-II-2018-List-of-DU-Goods-and-Technologies-and-Munitions-List-Dec-18.pdf https://www.wassenaar.org/app/uploads/2018/12/WA-DOC-18-PUB-... [2] https://en.wikipedia.org/wiki/United_States_national_missile_defense#Current_NMD_program https://en.wikipedia.org/wiki/United_States_national_missile...
- DaniloDias 7y agoEvery map in China is wrong. https://youtu.be/L9Di-UVC-_4 https://youtu.be/L9Di-UVC-_4 Pretty significant indicator that the intention is for military applications
- bgee 7y agoSaw 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 http://www.thespacereview.com/article/1307/1
- not_a_cop75 7y agoOh, look. It's the bigger penis argument all over again.
- dang 7y agoPlease don't do this here.
- mrtri 7y agoit's all landbased, the signals come from towers , satellites dont exist. prove me wrong