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China Begins Using New Global Positioning Satellites
cswilly writes with the news that China's satellite navigation system, called Beidou, has been successfully activated. "With ten satellites now, 16 in 2012, and 35 in 2020, China is making damn sure they are independent of the U.S. military's lock on GPS. According to the article, 'Beidou, or 'Big Dipper,' would cover most parts of the Asia Pacific by next year and then the world by 2020.'" The BBC also has slightly more detailed coverage.
the more the merrier.
You can't handle the truth.
China has a huge amount of their own infrastructure, so this isn't really surprising. Unlike U.S., China likes to do everything themselves. This also means you're not dependent on other countries like the U.S. is. What you don't understand is that China thinks long term, and everything they've done will grant them the leading country status some day, probably even within 10-15 years, especially when considering how much U.S. and EU are struggling now after thinking only short term financial gains.
You're thinking of sharks.
"National Security is the chief cause of national insecurity." - Celine's First Law
China does everything themselves because that makes sense to them at the moment. In fifty years they will probably be outsourcing and not maintaining their infrastructure.
--- Justin Dearing http://www.justaprogrammer.net/ We're just programmers.
we have car navigation systems that use Beidou for some time now (maybe less than a year).
Umm... you are aware of the differences between China and Japan, right?
Such as, say, a massive difference in population? A massive difference in natural resources? The fact that China is now locking up energy and mineral resources around the world which will deny their use to the USA in 50 years?
China and Japan are in no way comparable in this sense. You WILL be second fiddle to China. You can like this or not, but that's the simple reality. You almost are already. You will be passed within a few years, and continue your downward slide as the world aligns more and more to the number one world power of the future: China.
From what I can tell from the Wikipedia article, Beidou is an active system where the "client" sends data to the satellites in orbit. It makes perfect sense for the Chinese though, because now they can track where their users are -- something not possible with the passive US system since the receivers only receive and can't transmit any data back. In short, Big Brother Beidou always knows where you are.
Seems like an active system has a huge disadvantage, though. You can DOS the satellites by pointing an antenna at each satellite and jamming their uplink frequencies, knocking out the whole system for everyone, everywhere. In the US system, you can only jam local terrestrial reception and anybody over the next hill won't be affected.
DRM 'manages access' in the same way that a prison 'manages freedom'
Something I didn't realize until recently is that in the northern latitudes (Canada, northern US), GPS coverage has occasional small gaps in it. My John Deere dealer was saying that in some areas every few days about 6pm (happens to be that time in those areas) GPS coverage drops below 1 meter accuracy levels, and in those areas GPS guidance on farm machines becomes unusable for about an hour or so. As well sometimes a satellite goes offline for maintenance. As agriculture is becoming very reliant on GPS (hence John Deere lobbying in washington against LTE usage of adjacent frequencies), this is a problem. Because of this John Deere now uses GPS and GLONASS together to get better coverage. When Galileo provides coverage, it will use those signals too. The point is, more GPS systems simply improve reliability for everyone, if the Chinese allowed western use of their signals.
Would be possible to get a more accurate position if a receiver combined the various GPS systems - as a kind of check/balance. For non-military use the GPS systems introduce inaccuracies. Is there an algorithm that would bring the resolution down from 10 meters to 1 meter or less?
-CF
Well, a chinese spokesperson was quoted "They are as peaceful as the american GPS satellites, and contain no more armaments than those do" - so no worries.
We do have some strange reports of a high-ranking american general running from the press conference with a panic-struck look on his face, but that's probably unrelated.
It's The Golden Rule: "He who has the gold makes the rules."
Not this shit again. It looks like the shills from China are getting to the point where they even infect Slashdot.
Want to know one thing China lacks? The ability to grow food for its people. As of now, they are an exporter. Give it 10 years, and that isn't going to be the case. If the US gives a middle finger to the world, the country can keep its population fed. May not have the variety, but people would survive. Other countries would have mass starvations if it wasn't for their imports.
We have heard the second fiddle to China thing before. We were going to forever be second fiddle to Japan. We were going to be swallowed up by Communist countries because the USSR had so much land, puppet governments, and did not hesitate to use brutal force when called on. We were going to be swallowed up by every nation in the world going under Sharia law.
Not to say China isn't doing their part. The one thing China is good at is sabotage. They are going ape-shit dumping solar panels for way below the cost of materials + labor in the US market in effort to kill that industry and take it over for themselves. Instead of innovation, this is how they go about doing things. Hopefully in the fall of next year, we get a Congress elected that actually abide their oath of office and actively stop this crap.
The US has its faults. In fact, sometimes you wonder what the country does right, but like a NoSQL database where you wonder where the hell the consistency comes from but keeps its integrity over a period of time, the US keeps going.
China owns a trillion dollars worth of US debt.
With the dollar dropping by half in value, they've lost 500 billion dollars in purchasing power.
They do this to keep products cheap enough to sell to the US so they population has work and won't get antsy. They build empty cities for similar reasons (well actually I can't comprehend exactly why they build empty cities and empty buildings- it seems goofy).
China being a huge country is not an asset, it's a liability.
They do have a good legal lock on assets- but many of those assets are only rare at the current prices. As soon as rare earth prices go up 50%, millions of tons of rare earth can come on line- including a huge mine in the US.
About the time they stop building empty cities, the demand for copper and other building materials is going to drop through the floor.
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The US leadership class appears to have lost it and descended into greed.
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The true threat to the work is not china or the US but the corporations and the top 1%. And it's almost certainly two decades too late to do anything about it.
She was like chocolate when she drank... semi-sweet at first and then increasingly bitter.
I'd say it's already started, but the decline is a slow process. Empires don't so much fall as decay. It took longer for the Roman Empire to completely fall than the United States has even existed. If you want to put a timeline on it, I'd say the decline started post-WW2. We had a good run shortly after as the sole manufacturing powerhouse of the world, but that wasn't going to last forever.
Bear in mind we are *still* one of the biggest centers of industry in the entire world though. We're just having to adjust to not being #1 by giant margins in every sector imaginable.
Yes. This has been done for many years in survey equipment. a typical combination of Navstar (U.S. GPS)/GLONASS increases the number of satellites in view and therefore the accuracy. The biggest problem with combinging Navstar and GLONASS is that Navstar is CDMA (code division multiple access) while GLONASS is FDMA (frequency division multiple access). The former technique makes each satellite use a different "language" sort to say, while the later one uses different frequencies. The result is that a dual receiver needs two independent receivers, making them more expensive. New GLONASS satellites will start using CDMA signals in addition to the FDMA, so that legacy receivers work, and some time in the future new CDMA receivers can use both Navstar and GLONASS with a single type of tuner. Galileo was from the ground up designed to use CDMA and as a result, it is much easier to design a Navstar/Galileo dual receiver. As a matter of fact, many survey devices designed for Navstar can be upgraded via a firmware update to use Galileo as well. You can't upgrade to use GLONASS with a simple firmware update, you also need another tuner.
Regarding accuracy, the thing is that you can't go much less than 5m by just adding more satellites. This is because this error is part of ionosphere delays, and more satellites can't correct this error. It is like trying to do a measurement by averaging 1000 readings, but all done with a bad ruler. At some point, you need to figure out how good your ruler is. And the problem is that this changes dynamically so standard Kalman filter techiques also stop being effective for better than 5m accuracy. There are two approaches for this: the first one is dual frequency, and this is in part how Galileo achieves better accuracy. The idea here is to exploit the dispersion property of the ionosphere. It works like this: different frequencies have different delays, so you send the same signal using different frequencies, measure the delay different, and solve for the ionosphere error. This is what survey-grade equipment do, but they do this by tracking the encrypted military P(Y) code, which is encrypted. The result is a dual frequency solution but full of hacks that make it unstable. This means, as soon as the signal is interrupted for a short time, you need to re-sync.
The other approach for sub meter accuracy come from differential GPS. This technique uses to close receivers, one with a fixed known location. By measuring the error on the known location, you can apply corrections to the moving rover. But for this you need a link between the two (radio, UMTS, GSM, etc) or some post-processing. In addition, you need receivers capable of recording RAW data and then doing some complex math.
The cream of the desert comes from using carrier-phase measurements. With this technique you can go up to cm accuracy. This requires tracking the actual carrier wave, and a very precise model of the earth or post-processing software. The accuracy comes at a price: very very unstable. You need clear blue sky and uninterrupted signals. Plus about 20 seconds to lock the signal, even after small interruptions.
So to answer your question: more satellites guarantee better consistency and readings, particularly in cities and urban landscape. But you can't go below 5m unless you enter differential GPS or dual frequency measurements.