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Galileo: Europe's Version of GPS Reaches Key Phase
another random user sends this quote from the BBC:
"The third and fourth spacecraft in Europe's satellite navigation system have gone into orbit. The pair were launched on a Russian Soyuz rocket from French Guiana. It is an important milestone for the multi-billion-euro project to create a European version of the U.S. Global Positioning System. With four satellites now in orbit — the first and second spacecraft were launched in 2011 — it becomes possible to test Galileo end-to-end. That is because a minimum of four satellites are required in the sky for a smartphone or vehicle to use their signals to calculate a positional fix."
There has been far, far too many delays and political fuckery with this. I'm glad to hear it is finally going online.
Satellite navigation is just very important to everything these days (it is the primary nav method for all planes, ships, etc). Having everything rely on GPS, and thus on the budget the US chooses to spend keeping it working, is not a good idea.
This will make things much more reliable since, after an initial hissing match, the US and EU settled down and the systems play nice together and you'll be able to get devices that use both for better accuracy and reliability.
because a minimum of four satellites are required in the sky for a smartphone or vehicle to use their signals to calculate a positional fix.
Lets be more accurate here. A minimum of 4 satellites are required to be in the sky that can be observed at the same time from the same point on earth. Hopefully these satellites are relatively close together, because otherwise they might never all be visible at the same time. And if they are, since they are in low earth orbit they will pass by relatively quickly and only be briefly useable during each orbit. So, if the orbits are close this may allow a little bit of testing, but the "system" is still too satellite poor to be of any real use for navigation (at least unless you combine the signals with info from other U.S. or Russian satellites).
I'm an American. I love this country and the freedoms that we used to have.
Yes
As we add satellites, even from different systems, the accuracy will get better. It is very cool.
Well, the US did have selective availability enabled for a while. Perhaps European civilians don't want to be affected by US decisions.
Why is Europe spending billions to create their own GPS constellation when the US government already went through the hassle and expense? The GPS system is free and open to use by anyone with a GPS receiver. This strikes me as nothing but a political move, as if to say "We're independent and don't need America to provide anything for us". This is a completely redundant and pointless project by the EU.
Sigh,
It is a measure of trust. No one, trusts that the US will not screw with GPS if it would give them a military or economic advantage. Sure they say right now that they won't, but who knows what will happen in 5, 10 or 15 years in the future. And trust me, the value of an accurate navigation/timing system makes it well worth the efforts the Europeans, the Russians and the Chinese are making to field their own versions.
Why can't we all be friends?
They'll arrive. There are already devices that can receive both Soviet GLONASS and GPS (e.g. Galaxy SIII) to get better positional accuracy. Soon the new devices will receive Galileo as well, for triple redundancy and improved accuracy.
That must be exactly what Russians think about us not wanting to use their fine space launch services indefinitely.
When your international reputation is at an all-time low you should expect things like this... Galileo was started way before the US popularity took a nose dive, but the last decade or so are only going to make projects like this *more* likely. To the civilised world, the US is not one of the good guys any more, they're not in "bad guy" territory yet, but they're sure headed there fast.
Basically the world no longer trusts the USA. Simple as that.
Simon.
Physicists get Hadrons!
Are there any consumer gear that can receive Galileo?
I don't see how this could possibly be called a Chicken and the Egg type problem, as the satellites are are already in space to support consumer devices. They obviously didn't need consumer device support to get things started at all.
In Asia China's Beidou/Compass should be interesting now, and we'll see how quickly the next phase comes along.
And Japan's QZSS is easily usable by GPS receivers with the right software.
Why is Europe spending billions to create their own GPS constellation when the US government already went through the hassle and expense? The GPS system is free and open to use by anyone with a GPS receiver. This strikes me as nothing but a political move, as if to say "We're independent and don't need America to provide anything for us". This is a completely redundant and pointless project by the EU.
Even as an American I can see the value in having a completely separate system for satellite navigation. Even ignoring the ability of the USA to reduce the accuracy (or completely shut off) the system, the system is still a potential single point of failure subject to software problems or a rogue agent controlling the ground stations. Much better to have a completely separate redundant system with no common elements.
Your comment is short-sighted.
GPS, whether American, Russian, or EU, is first and foremost, a military asset for their respective owners.
The US military can elect to disable or cripple civilian GPS service to all devices other than their own when they deem it necessary to prevent its use by hostile forces. Presumably, GLONASS and the EU systems have the same capability.
History repeatedly shows that international political alliances vary over time. Just because we currently are at relative peace with the EU and Russia, that does not mean it will always be so in the decades to come. I'm not saying we will be in a hostile situation with either in the future, but it's not out of the realm of possibility, either.
The EU is building their own system not because they want to win a "pissing match" with the US or Russia. It would be foolish of them strategically to depend on a GPS that is under someone else's control.
Let's play Four Horsemen of the Apocalypse. I'll be Pestilence.
Jesus, tunnel vision much ?
Look it's nothing to do with GPS vs Galileo. It's to do with the USA, a nuclear power, declaring war left, right and center, & invading other countries basically because it can. No-one likes that; international reputation suffers, trust is lost, and consequences ensue. There's no point in getting pissy about it, you brought it on yourselves.
I don't think Europeans are innately superior. I think people are just people, wherever you are. I'm married to an American woman, whom I love dearly. I do think the USA is fucked though, the society is (IMHO) past the tipping point and heading down, and I can't see myself staying around much longer, as I've said before on this site. At some point, the money just ain't worth it.
Simon
Physicists get Hadrons!
You need at least one other sat to fix you in time. The receiver doesn't have an atomic clock and so needs an extra point of data for the extra unknown.
Simple logic might win an argument, but that doesn't make you correct.
I think destroying the satellites would be the equivalent of a declaration of war. I'm not sure the U.S. would want to declare war on its allies.
Of course should the U.S. and Europe no longer be allies at the time that happens, then if the U.S. kills the Galileo satellites, I guess Europe's answer would be to kill the GPS satellites. Again, not exactly what the U.S. wants.
The Tao of math: The numbers you can count are not the real numbers.
No, that's just plain wrong. It is not sufficient to know the exact time at three transmitters to get a 3D fix. You'd also need to know the exact time when the signals are received, which is a very difficult (read: costly) problem. The accuracy of the positioning information is limited by both the precision of the satellite clock signal and the accuracy of the receiver clock signal. The latter can be removed from the equations by using a fourth satellite signal, but not by providing better satellite clock signals. And you really need to stop calling people names, especially when you're so obviously out of your depth.
"Hm, what was the last time Congress declared war? Or are we just making shit up now?"
Note the "invading countries left, right, and centre" part of his argument too, the US has been doing this basically without a single break since World War II in one way or another, whether it's drone strikes in Pakistan, or the CIA pulling off defacto coups across the world. His point is that America spends far too much time and far too much money meddling with other nations, rather than keeping to itself, and that often leads to greater instability. Case in point, by ousting Saddam, the US removed the only credible counterbalance in the middle east to Iran, and since then Iran has been able to carry out proxy attacks everywhere from Iraq, to Lebanon, from Afghanistan, to the Philippines. They couldn't do this shit when Saddam was around, because Saddam would then be given the international blessing he needed to do the exact same thing in Iran proper. By trying to make things better for the oppressed minorities in Iraq, the US ended up making things worse for everyone in Iraq, and people in many other countris too. So when you stop avoiding the point he was making by focussing on a specific intentionally mis-used part of that, tell me, are you disagreeing that America consistently meddles in the dealings of other nations?
"Well, a lot of your countrymen do"
Well, ignoring the fact Europe is a country, what Europeans thinks is not that they have any kind of innate superiority - that's simply not in the European mindset- Europeans are simply much more rational than that, they recognise their fallibility in part because they have thousands of years of history of it to learn from. Some European nations did have this mindset- the French and British at the height of their empires for example, but as their empires fell they realise it was simply a load of bullshit. Ironically, the reason you most likely claim it is because it IS something that's in the US mindset, there's even a term for it - "American exceptionalism", it's something America hasn't, like Europe, grown out of yet.
What many Europeans do believe however, that you're getting confused with, is the fact that currently, Europe is at least governing itself just a little bit more sanely than the US, and that is what Europeans are happy to point out to you. The terms you mention are nothing more than banter, and if you believe any use of them implies some perceived superiority then it simply demonstrates that you, as an American, haven't got out of this absurd mindset that some nations and their people are simply inherently superior to others. Europeans know full well they have their problems, and this is ironically why the current global economic instabilities focus on the Eurozone's issues - because Europe is the only one really openly admitting they have a big problem and trying to deal with it, in contrast to for example America's insanely massive deficit, see here for example, and sort by worst to best, note how insanely large the US figure is in the negative compared to even the closest member on the list?
http://en.wikipedia.org/wiki/List_of_sovereign_states_by_current_account_balance
The only reason you believe there's some kind of belief about inherent superiority is because you have that mindset yourself, until you lose that you wont be able to get over this stupid idea that Europeans think they are innately superior. Believing they are doing some things better that lead to for example, lower infant mortality, longer life expectancy, higher levels of personal happiness, etc. does not in any way imply this is because of some innate superiority or belief in such.
Please stop voting this guy up, while simultaneously voting down the numerous posts that are correct.
Four satellites are required because there are four unknowns, and only one measurement per satellite available, irrespective of precision or lack thereof.
Here's some quotes from Global Positioning System so we can all stop agreeing with the loudest person instead of the facts:
"About nine satellites are visible from any point on the ground at any one time, ensuring considerable redundancy over the minimum four satellites needed for a position."
"The receiver uses messages received from satellites to determine the satellite positions and time sent. The x, y, and z components of satellite position and the time sent are designated as [xi, yi, zi, ti] where the subscript i denotes the satellite and has the value 1, 2, ..., n, where n >= 4."
"Although four satellites are required for normal operation, fewer apply in special cases. If one variable is already known, a receiver can determine its position using only three satellites. For example, a ship or aircraft may have known elevation.
The time precision required for a fix of any reasonable accuracy requires atomic clocks. You can't carry atomic clocks in your pocket, they're a tad too big for that. There is no way to know the time on the satellites from the ground, because you don't know where you are, and hence how far the satellites are from you, and hence the delay added to the signals. You can use three satellites to figure out where you are, if you know what time it is, but you don't. Adding a fourth satellite in the mix lets you solve for all four unknowns in the equation. Note the exception in the wiki article applies only in some rare cases, like the GPS units used by ships, not the GPS units handed out to most military personnel.
THIS HAS NOTHING AT ALL TO DO WITH SELECTIVE AVAILABILITY.
The military encryption simply reduces the precision of the solution, it doesn't actually change the number of unknowns and hence the equations in any way. A civilian marine GPS could locate itself with just 3 satellites even with selective availability enabled, as long as it assumes that it's at 0 elevation. In all other cases, four satellites are required, even for military units.
Let's go one satellite at a time...
First satellite: You know approximately what time it is because the satellite tells you. You know the position of the satellite, and all of the other satellites, because it tells you in its signal. However, you don't know how far away the satellite is because you don't know the difference in time between when it sent its signal and when you received it. Thus, while one satellite tells you a lot, it does nothing at all to narrow down your position.
Second satellite: Now you know the difference in time between when you heard the two satellites, and thus, you know how much further you are from one of them than you are from the other. So in 3D space, you can use this information to narrow down your position to a point that lies on a sphere. This sphere intersects the earth, forming a circle. Thus, you know a lot of place where you might be, but you still really don't know much.
Third satellite: Now you're able to cut that huge sphere down to a circle. Where this circle intersects the earth, are two points. One point is flying around at high speed, the other relatively stationary. Thus, you kind of know where you are now. ...but only kind of. While the earth is a sphere and we intersected that with a circle to get two points, the places on the earth you might be aren't an infinitely thin mathematical sphere. There's thousands of feet of elevation in which you might exist. ...and worse than that, even if you don't care to know your elevation, the intersection of that circle with the atmosphere isn't straight up and down -- it's at some bizarre and slowly changing angle -- thus you can't ignore it because it isn't just your elevation you don't know, but rather, you're equally uncertain about your latitude and longitude. You know your position to within a mile or so, but if you want to be more accurate than that, you need to either know your elevation or find another satellite.
Fourth satellite: That circle of possible locations is now narrowed down to two points. One is flying randomly through space, the other is near earth. You don't even need to find an intersection with the surface of the earth, unless by some odd chance you're having difficulty figuring out which of those two points is you.
Fifth satellite: No longer any questions, you know exactly which point is you. ...but still, the math is only narrowing you down to about a 10 ft. radius...
Sixth satellite: ...and so it's nice to have some additional data to average together for a slightly more accurate result.
Seventh satellite: ...and it's nice to have some spares for when some become obstructed by trees or tall buildings.
But I do know just a little about it.
Which seems to be the amount you know about everything.
That's not helpful.
GPS recievers indeed solve a 4D problem (3D space + time) which requires
4 sats. As expensive as the military units are, they may be able to bridge reception
gaps by keeping time by themselves for a while, so may for a while work with
only three sat signals.
But without a local timer with the precision of an atomic clock, that's the digital
equivalent to dead reckoning, and will only get you so far until you need your fourth
sat again.
Of course, if you are the Navy, one of your coordinates is known by default (at least
plus or minus a couple of meters), so maybe their gear is permanently set to a dedicated
2D mode. That would indeed work with 3 signals - but you still need four inputs for a 3D
position, it's just that in this case one of those inputs doesn't come from space, but from
looking out the window.
Maybe you will believe the Los Alamos Labs' GIS unit?
"If you require 3-dimensional coordinates (northerning, easting, and elevation), a minimum of four satellites is needed."
Nevertheless, I am still correct. The 4th sat is only for precision.
No it's not.
It is not necessary for location.
Yes it is.
Quoting the Navy: "Therefore there are 4 unknowns at each timeline where a solution is computed, 3 for position and 1 for time. This is why the minimum number of satellites for a solution is 4."
While "selective availability" (the intentional degradation of civilian signals to roughly 100m accuracy) has been disabled for a while and the new satellites don't have the capability for implementing it, the military does indeed have separate signals for civilian and military users.
Referring to the wikipedia, the civilian signal ("C/A") is only transmitted on the L1 band at 1575.42 MHz. The encrypted precision codes (for the military) are transmitted on both L1 and L2 at 1227.60 MHz. The military signal is indeed quite a bit more accurate than the civilian signal: by itself, the civilian GPS signal is only accurate to around 3 meters. The military signal is accurate to around 30cm.
With current civilian signals only transmitted on a single frequency, receivers cannot correct for ionospheric conditions (which composes a major part of the current uncertainty in measurements) as doing so requires two frequencies. Military signals are transmitted on two frequencies so receivers can correct for ionospheric delay. The military signal is also transmitted at a much higher rate (10x the civilian rate), yielding proportional increases in accuracy.
Currently there are systems like WAAS (North America) and EGNOS (Europe) that provide augmentation in the form of corrections for ionospheric delays (and some other information, like current "health" status of the satellites). This can improve accuracy even more (my handheld civilian unit is able to compute position with an uncertainty of 2 meters). EGNOS also provides an internet feed of the augmentation data so one doesn't have to have a clear view of the geostationary satellites that provide the augmentation. WAAS only augments GPS, but EGNOS augments GPS, GLONASS, and Galileo (for what it's worth at present).
The GPS upgrades will add more detailed signals (the civilian signal will be broadcast on L1 and L2 as well as safety-of-life signal on L5 at 1176.45 MHz). The military codes will also get an upgrade as well, but that won't really matter for civilian users. With the civilian signals being transmitted on a total of three frequencies it will be possible for receivers to account for ionospheric delay and other factors. Overall, things will get considerably more accurate.