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.
Is the error consistent over a few hours, or does it jump around
whimsically?
Xho
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