Re: Google Earth: Elevation of water?

Terry Pinnell <terrypinDELETE@xxxxxxxxxxxxxxxxxxx> wrote in
news:rdv6h1l2o223i7167lggrc290deb4u7pog@xxxxxxx:

> Maybe you misread my post. I was asking why GE reported a small lake's
> surface at 'elevations' varying widely (50 ft or so) across a few
> hundred feet horizontally. I was guessing it must be reporting
> *ground* elevations.
>
GPS reports the elevation it *thinks* it is above MSL, whether it's on
water, land, or anything else. The receiver doesn't know the elevation of
any point, but gets the elevation from the satellites. This is very
imprecise, and varies with the satellite geometry. This is the reason for
WAAS, to provide altitude with greater precision for aircraft, not for
greater horizontal precision. That is just a side effect. You will see
different altitude reported at the same place, depending on the time and
the satellites received, and their relative locations. Altitude is far
less accurate than horizontal location.

--
Regards,

Stan

"They that can give up essential liberty to obtain a little temporary
safety deserve neither liberty nor safety." B. Franklin
.

Relevant Pages

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