magnetic offset and the shift of the planet?

[Julian]

In among all the bickering about how poorly acted and how mediocre the directors are on the bbc contrived disaster film being played out at top, the purple people eater mentioned that the earth has been shifted by up to 25cm off axis.

Now this seems awfully small, but these things often play out to make changes we could not foresee or understand straight away.

Now am not a fool, but I only studied physics to 'A' level for my sins and I was wondering if a shift like this might affect the earth's magnetic field in any way?

Also, would all the satellites move in relation to the earth or will they all require calibrating to cope with an unexpected move of the planet. Might this also change our wobble and how might this pan out?

p.s. my thoughts and real concerns go out to the people (another island race) who are suffering immeasurably in Japan right now, I can't imagine how frightening it must be, added to the grief of those who are losing whole families and livelihoods. I also don't believe as some appear to that this whole disaster is the fault of the bbc.

[Arghiro]

25cm, or less than a foot? I doubt that GPS is that accurate, even with Differential algorithms applied. I can't see something that small affecting anything the you & I could measure.

And, yes, what has happened (and still happening) in Japan is horrendous. Probably one of the best prepared countries (and richest) in the world for such disasters, and utterly powerless to stop it. But I reckon the death toll & devastation would have been far far higher if Japan hadn't worked so hard to build earthquake resistant structures.

[Julian]

25cm, or less than a foot? I doubt that GPS is that accurate, even with Differential algorithms applied. I can't see something that small affecting anything the you & I could measure.

Do you think? I think quite the opposite with the distances involved, 25cm could mean quite an induced error no? A quick search shows GPS satellites at 12,000 miles above the earth, basic trig would make a 25cm shift quite significant.

The GPS sats are not geo-stationary so maybe my question will be more relevant to communication sats where* I guess that 25cm will hardly make a dent.

It's too early and my maths is too rusty to have a go at some real figures.

None of this is ego massaging or in any way negative, I am genuinely interested if something like this will make a difference.

The fact that nothing has been said and aircraft are still flying without problem would make one assume that little if any difference has occurred in the real world.

*can't decide if that should be were or where, I went with where as I was referring to an area or group, is that okay AlanT???

[DaveS]

Elsewhere, or maybe later in the same report, it was mentioned that the main Japanese island had moved 2.4 metres. I would have thought that quite sufficient to upset road use sat navs unless they use DGPS. Anyone know?

[Arghiro]

Elsewhere, or maybe later in the same report, it was mentioned that the main Japanese island had moved 2.4 metres. I would have thought that quite sufficient to upset road use sat navs unless they use DGPS. Anyone know?

Again I doubt it. I don't think that maps are that accurate. Remember that a road marked on a map is much larger than reality. If you scaled up the average road marked on a map I suspect it would be about 100mtr wide. At max magnification, my google earth GPS often shows me driving thro fields alongside the road anyway.

[Telo]

my google earth GPS often shows me driving thro fields alongside the road anyway

So now we know why you were pushing the car when you did your leg in.

[Arghiro]

my google earth GPS often shows me driving thro fields alongside the road anyway

So now we know why you were pushing the car when you did your leg in.

Actually, I had stopped across a driveway to sort summat out & the owner of the house came back - but the car wouldn't restart. So I tried to push it out of the way . . .

I am not as fit & young as I used to be. or I thought I was!

[DaveS]

Elsewhere, or maybe later in the same report, it was mentioned that the main Japanese island had moved 2.4 metres. I would have thought that quite sufficient to upset road use sat navs unless they use DGPS. Anyone know?

Again I doubt it. I don't think that maps are that accurate. Remember that a road marked on a map is much larger than reality. If you scaled up the average road marked on a map I suspect it would be about 100mtr wide. At max magnification, my google earth GPS often shows me driving thro fields alongside the road anyway.

I think it depends on both the hardware and the mapping software. I've just bought one of Maplin's GPS dongles and tried it for the first time last night. It comes with a trial application that shows position on a Google Earth map. With 4 satellites acquired (this inside a stone built house) it consistently showed a position within 2 metres horizontally and 4 metres vertically of reality.

Back to car sat navs: their road data is held in vector format so shouldn't be subject to scaling effects. I know that mine (a Navman) realises I've left a motorway when I'm about half way down the slip road, maybe 3 metres to the side of the main carriageway. This is what made me wonder about the effect of the Japanese 2.4m shift.