"Pathfinders" Take Shape For Galileo, Europe's GPS 105
oliderid sends along a BBC report on progress toward Europe's home-grown GPS system. The Galileo concept will get an initial test via four "pathfinder" satellites that will be the first in the Galileo constellation. Galileo is intended to be complementary with the US GPS system — when all 30 Galileo birds are flying, a receiver with both GS and Galileo capability should enjoy 1-meter positional accuracy, vs. the several meters available through GPS alone, according to the article. There's a video tour of the facility where the pathfinders are being built. "After all the wrangling, the delays, and the furor over cost, Europe's version of GPS is finally starting to take shape. Due for launch in pairs in late 2010 and early 2011, the 'pathfinders' will form a mini-constellation in the sky. They will transmit the navigation signals that demonstrate the European system can become a reality."
Re:Funding (Score:4, Informative)
> How are they getting funding? As recently as yesterday I was reading about how it was pretty much an orphaned project because no one wanted to buy what was already available for free (albeit less reliably).
I can not remember the full story, but the industry funding arguments dragged along for years, and in the end the EU took over funding of the project (it was too high profile to fail !!).
http://en.wikipedia.org/wiki/Galileo_(satellite_navigation) [wikipedia.org]
Re:Funding (Score:3, Informative)
Re:general relativity at work (Score:1, Informative)
What I think is really cool about GPS is that without Einstein's theory of general relativity, it wouldn't work.
Oh, it would work just fine alright, in fact it would be a heck of a lot simpler to build and maintain, and probably somewhat cheaper, too. The folks that built the satellites and the base station that sets each satellite clock would have much less headache.
See:
http://www.metaresearch.org/cosmology/gps-relativity.asp [metaresearch.org]
which claims to be a rehash of a chapter of the book "Open Questions in Relativistic Physics"
"Rather than have clocks with such large rate differences, the satellite clocks are reset in rate before launch to compensate for these predicted effects .... Therefore, we observe the clocks running at their offset rates before launch. Then we observe the clocks running after launch and compare their rates with the predictions of relativity, both GR and SR combined. If the predictions are right, we should see the clocks run again at nearly the same rates as ground clocks, despite using an offset definition for the length of one second."
Re:Funding (Score:2, Informative)
Re:Time service (Score:2, Informative)
There was a point in time where the Russians didn't have the money to maintain the system, however that has changed, and I believe they have been adding sattelites to bring it up to full capacity.
Re:EU Vehicle Tracking Plan (Score:3, Informative)
If the US switched off GPS, then we wouldn't have GPS either.
GPS is not "switched off". Instead, "Selective Availability" (SA) is turned back on.
SA introduces random, unpredictable errors into the unencrypted signals broadcast by the GPS satellites. As a result, the accuracy of a position decreases. When the GPS system first went online and SA was still enabled, typical position accuracy was about within 10 meters:
http://en.wikipedia.org/wiki/Global_Positioning_System#Selective_availability [wikipedia.org]
SA can still be enabled (introducing errors up to 100m), and can be enabled for only certain parts of the globe. But, it only degrades the unencrypted broadcast. The encrypted signal used by the military is not affected.
Re:Funding (Score:3, Informative)
It's short a few satellites for whole world coverage right now. Now that Russia has oil dollars running in, the whole world should be back up in a year or so... they've been launching satellites quite frequently the last few years.
Here is a map of current coverage.. basically everywhere except Antarctica.
map [glonass-ianc.rsa.ru] A few pieces are missing here and there, but it's a far cry from "just russia".
Re:general relativity at work (Score:2, Informative)
It took a couple of readings of the post at the top of this thread to figure out what it was trying to say.
Re:The EU system won't get used (Score:3, Informative)
[quote]Assuming the US stick to their promise to keep SA turned off...[/quote]
Well, turning on SA would screw airplanes everywhere, and new GPS III satellites aren't going to have SA (this was announced in 2007 so it may have already started), so it is pretty hard to not keep their promise.
Re:general relativity at work (Score:3, Informative)
The GPS satellites orbit at about 12.5 thousand miles with an orbital period of about 12 hours. They are synchronous with the sidereal day and not geostationary.
The GPS satellite clocks lag by about 7 microseconds per day do to their velocity (special relativity) and lead by about 45 microseconds per day do to their orbital distance from earth's gravity well (general relativity) compared to an earth bound clock.