"Geoff Schultz" wrote in message
7...
I was watching the NBC nightly news tonight and they stated that the
rotation of the Earth was effected by the tsunami. According to the
report
the day of the tsunami was slightly shorter than standard day, which would
mean that the roation increased slightly. They didn't state if the
rotational change was permanent of a 1 time event.

I was wondering if this induced an error in GPS positioning as the Earth
isn't where it is expected to be. In my way of thinking we shifted
slightly easterly. I have no idea how much of a change this is, or even
if
it's measurable withn the error of a GPS, but it's an interesting
question.

-- Geoff

I had heard a CNN comment that the quake "has changed the geography of the
globe" and they then went on to explain that the NW tip of Sumatra "may have
shifted up to 160 feet." OK, that's two degrees of weasel-words ("may have"
and "up to"), and I find a 160-foot lateral shift to be incredible. IIRC,
they also said that the Earth's rotation was slowed by 10 milliseconds per
day. That's not very much, only about one part in 864,000. or about
0.00001%.

However, if the Earth's rotation has been affected, the GPS system would be
corrected within a day or so (maybe quicker). The satellites are
continuously monitored for orbital deviations by checking the results of
positions of benchmarks. I think the satellites are corrected on every
orbit, or at least some relatively frequent schedule.

At first, you might think this was just a one-day aberration, but if you
redistribute enough mass on our rotating globe, you should be able to make
permanent changes in the rotational velocity. And that makes me think it
might be a permanent change (permanent until the next big mass
redistribution event).

Where's an orbital mechanic when you need one?

Ed
wb6wsn