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buckman
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 Posted: Tue Jan 25, 2005 10:31 am Post subject: Could the Tsunami cause this??? |
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Just read an Article that because the Tsunami caused the Earth to move on its Axis , that some/most Satellite Navigation products can be thrown off course slighty??
Is this true?? As from the start of the year (maybe coincidence) my TomTom Go seems slightly sluggish and got its self lost the other day!! which is out of charachter?
Is this coincidence? or is there something in it?? |
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buckman
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| Posted: Tue Jan 25, 2005 10:33 am Post subject: |
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Although i should point out that this was a massive disaster and i suppose i or we shouldnt be worrying if our Satnav is a little "out"
Just read it back and i hope people didnt think i was being selfish or dis-respectful, as these people have lost everything...  |
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gingernut777
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Joined: Nov 03, 2004
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| Posted: Tue Jan 25, 2005 10:58 am Post subject: Re: Could the Tsunami cause this??? |
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| buckman wrote: | Just read an Article that because the Tsunami caused the Earth to move on its Axis , that some/most Satellite Navigation products can be thrown off course slighty??
Is this true?? As from the start of the year (maybe coincidence) my TomTom Go seems slightly sluggish and got its self lost the other day!! which is out of charachter?
Is this coincidence? or is there something in it?? |
I wouldn't worry about it.
The world as a way of sorting itself out, with or without "The Experts"
Look what happened when Krakatoa blew itself apart. Distruction yes, but the world is still going strong.
As for GPS positioning,, I'm still shown exactly in the same position as before.
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nej
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| Posted: Tue Jan 25, 2005 11:47 am Post subject: |
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| Technically yes, although it's something like 1 micro-milli-trilli second out over a thousand years or something. |
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gingernut777
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| Posted: Tue Jan 25, 2005 12:45 pm Post subject: |
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| nej wrote: | | Technically yes, although it's something like 1 micro-milli-trilli second out over a thousand years or something. |
better re-set my watch then!
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Sniff
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Joined: Nov 02, 2004
Posts: 123
Location: Munich, Germany
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| Posted: Tue Jan 25, 2005 2:14 pm Post subject: Re: Could the Tsunami cause this??? |
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| buckman wrote: | Just read an Article that because the Tsunami caused the Earth to move on its Axis , that some/most Satellite Navigation products can be thrown off course slighty??
Is this true?? As from the start of the year (maybe coincidence) my TomTom Go seems slightly sluggish and got its self lost the other day!! which is out of charachter?
Is this coincidence? or is there something in it?? |
Actually the cause is more likely to be the earthquake (which caused the tsunami), rather than the tsunami itself. Sounds feasible, but microscopic distances hardly worth worrying about |
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fitshase
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Joined: Dec 03, 2004
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| Posted: Tue Jan 25, 2005 7:39 pm Post subject: |
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Yes, it's true, the earth moved by about 2cm. However, the TTGO is only accurate to 10m so I don't think 2cm will make much difference.
Fitshase |
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Dazp
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Joined: Nov 25, 2004
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| Posted: Tue Jan 25, 2005 8:45 pm Post subject: |
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Surely it makes no odds anyway, as the TTgo is picking up signals from several satallites that are orbiting the earth... as long as they are orbiting and sending signals they will give you your position as before.. whether the earth has moved or not...  thats how I tho't it worked any way..! |
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lbendlin
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Joined: 02/11/2002 22:41:59
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Location: Massachusetts, USA
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| Posted: Tue Jan 25, 2005 9:39 pm Post subject: |
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Over in Europe it may only be a shift of 2 cm but in the desaster area some islands have been moved around by 30 meters. Especially for marine navigation this does already have some impact, and as far as I know they started redrawing the maps.
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Sniff
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| Posted: Wed Jan 26, 2005 9:38 am Post subject: |
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| Dazp wrote: | | Surely it makes no odds anyway, as the TTgo is picking up signals from several satallites that are orbiting the earth... as long as they are orbiting and sending signals they will give you your position as before.. whether the earth has moved or not... thats how I tho't it worked any way..! |
I assume they are receiving satellite signals and using an algorithm to relate those signals to a fixed earth position. If the earth has actually moved 2cm one way, that algorithm will now not be accurate, it'll be 2cm out. |
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calypso
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| Posted: Wed Jan 26, 2005 10:37 am Post subject: |
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Oooh! Your're right.
I was wondering why Jane said "You have almost reached your destination yesterday.
Clever sausage! :D
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Oldboy
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Joined: Dec 08, 2004
Posts: 10641
Location: Suffolk, UK
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| Posted: Wed Jan 26, 2005 11:36 am Post subject: |
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Surely the satellite positions are calculated from ground stations. In which case there should be no variation in position - in theory!!
R |
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Sniff
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| Posted: Wed Jan 26, 2005 11:54 am Post subject: |
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| Oldboy wrote: | Surely the satellite positions are calculated from ground stations. In which case there should be no variation in position - in theory!!
R |
The satellites are in geostationary orbit...ie they are in fixed positions and their location as seen from Earth does not vary. That's how GPS works... The unit times how long a signal takes to reach you from a known satellite position, and uses that to calculate exactly how far from that satellite it currently is. Assuming you can get a signal from three or more satellites you can use triangulation to calculate your actual physical position on the planet (give or take the allowable discrepancies in the GPS system) |
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nej
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| Posted: Wed Jan 26, 2005 1:04 pm Post subject: |
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| I didn't think they were geostationary - that's why your receiver has to download the orbital and ephemeris information. |
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Oldboy
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| Posted: Wed Jan 26, 2005 1:40 pm Post subject: |
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If you go to the FAQ page and select 'Basic GPS Theory' then select 'How does GPS work' the answer given suggests that the satellites know their positions and can then pass that information on.
I might have read it wrong - I stand to be corrected.
Richard |
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