In article
<ctbishop-0405081353140001@[EMAIL PROTECTED]
>,
Charles Bishop <ctbishop@[EMAIL PROTECTED]
> wrote:
> In article <Pine.NEB.4.64.0805041029380.11619@[EMAIL PROTECTED]
>, Lee
> Ayrton <layrton@[EMAIL PROTECTED]
> wrote:
>
> >On Sun, 4 May 2008, Ray wrote:
> >
> >> On May 4, 1:27 am, Brettster <brett.ba...@[EMAIL PROTECTED]
> wrote:
> >>> My regular walk to the Beverly Hills Public Library seems like a
> >>> gradual uphill climb -- nothing on par with San Francisco, but a
very
> >>> slight incline most or all of the way. As you might expect, the walk
> >>> back home is a breeze. According to my handheld Garmin GPS, it's
> >>> exactly 1.75 miles each way. But I wondered exactly how much height
I
> >>> was achieving on my walk, in addition to the distance. How can I
tell?
> >>> Can a handheld device measure something like that? It could be
several
> >>> feet or, I suppose, it could be more. I have utterly no idea. Any
> >>> ideas?
> >>
> >> All gps receivers calculate altitude (as the calculated position is a
> >> point in 3D space, not just a horizontal position), but whether they
> >> choose to display it is up to the unit. As previously mentioned,
> >> altitude is notoriously inaccurate - this is because the algorithm is
> >> biased to give preference to satellites that are near the horizon, in
> >> order to improve horizontal accuracy. Mine can be out by over 100
feet
> >> or more.
> >
> >Data point: My car GPS (Mio) routinely re****ts my altitude to be some
25
> >to 30' higher than it actually is. Like two week ago when it re****ted
my
> >altitude to be 35', when I was parked in a lot about 8' above MSL.
>
> I understand the concept of MSL, but is it necessarily true that if you
> can see the ocean from a parking lot, the level of the ocean in that
spot,
> at that time, is MSL? If not, what + or - could be given to Lee's
> estimated 8'? That is, if MSL is maybe different from the level of the
> ocean in his parking lot, how much different is it likely to be?
>
> chrles, assume he wasn't parking near the Bay of Fundy, bishop
I've heard the difference in average surface levels between the two
sides of the Panama Canal is on the order of 11 inches, due to salinity
and temperature (don't know which is higher, but I suspect the Atlantic
since it's warmer). Don't know how true that is. What's the average
tide height around continents, 2-3 feet?
--
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