GPS navigation

David,

GPS is optimised for sea level, Blanchefort [a mountaintop ruined
castle] is 467 metres above sea level, couple this with a slant range
to a satellite of several thousand miles and the curvature of the earth
and you have error. At least up to 100 metres..."


That's just plain BS. Just one example: The space shuttle uses GPS for
navigation. That should be plenty high to convince the poster otherwise.

--
Thomas Borchert (EDDH)

Thomas Borchert wrote:
That's just plain BS. Just one example: The space shuttle uses GPS for
navigation. That should be plenty high to convince the poster otherwise.

Would an ordinary GPS receiver (say, my $99 eTrex) work on the shuttle? I
can see how the basic principles are the same, but I'm guessing my eTrex
wouldn't be happy with the speeds the shuttle is doing.

Roy,

I
can see how the basic principles are the same, but I'm guessing my eTrex
wouldn't be happy with the speeds the shuttle is doing.


Many cheaper GPS receiver do indeed have a speed limit. Is it given in the
specs for the eTrex?

--
Thomas Borchert (EDDH)

Thomas Borchert wrote:

I can see how the basic principles are the same, but I'm guessing my eTrex
wouldn't be happy with the speeds the shuttle is doing.

Many cheaper GPS receiver do indeed have a speed limit. Is it given in the
specs for the eTrex?

There are technology export regulations that limit GPS receivers to
operation below altitudes of 60 kft or below speeds of 1000 knots.
Most consumer models, including the eTrex, are specified to work up to
those limits. However, some units have lower limits - for example,
most Magellan models specify a maximum speed of 951mph.

On 2006-06-11, David W wrote:
"GPS is optimised for sea level, Blanchefort [a mountaintop ruined
castle] is 467 metres above sea level, couple this with a slant range
to a satellite of several thousand miles and the curvature of the earth
and you have error. At least up to 100 metres..."

Well, in a light plane cruising between 4,000 and 8,000 feet, my
handheld Garmin 195 reports an estimated position error of 13 feet -
about 4 metres. Your friend doesn't know what he's talking about.

The map is only optimized for aviation in that it depicts airspace - the
receiver itself and the way it generates the map is no different from a
GPS for use by sailors or drivers or hikers.

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