[time-nuts] Einstein Special on PBS
hmurray at megapathdsl.net
Sun Nov 29 15:41:07 EST 2015
tvb at LeapSecond.com said:
> I'm not sure I understand your elevation question. Are you talking about
> elevation as in mountain vs. sea level altitude? Or elevation as in
> satellite Az/El?
I was thinking of the elevation of the receiver as in mountain vs sea level.
I think the question I was trying to ask is: Do the calculations for a
consumer grade GPS include relativistic corrections for the elevation of the
receiver? How about a survey grade receiver?
kb8tq at n1k.org said:
> Most survey work is done as a “delta from known references”. It’s much like
> common view time transfer. That alone takes care of a whole raft of things.
I assume the delta includes elevation as well as lat/long. That may make
relativistic corrections insignificant.
A week or so ago, I stopped to chat with a surveyor working on a lot a block
from here. He was using old fashioned optical gear. (Standard story 42.
The house next door was built with reference to the fences. The fence was
off, so that house is actually too close to the lot line. His job was to
make sure the new house didn't get into similar troubles.)
He mentioned that GPS gear has the problem of plate motion. That's a bug if
you want to survey lot lines but a feature if you want to measure earthquake
fault creep. (Standard number is plates move about as fast as your
fingernails grow, ballpark of an inch a year. I'm a few miles from the San
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