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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.
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.
"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.