Re: Questions (Space)

In article <MPG.2155ec6e57c8b03098bb9a@xxxxxxxxxxxxxxxx>
gerryq@xxxxxxxxx "Gerry Quinn" writes:

In article <1189776908snz@xxxxxxxxxxxxxxxxxxx>,
ames@xxxxxxxxxxxxxxxxxxx says...
In article <1189770487.575366.119560@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
paul.clarke@xxxxxxxxxxxxx " Paul Clarke" writes:

Right, the longitude is a scalar and the latitude is a scalar.
The combination of the two of them that gives your position
isn't.

Actually, I think not. The longitude and latitude I'd say are
vector quantities (in spherical space coordinates); the vector
addition of them gives your location, another vector. But all
of those are merely spatial vectors relative to the coordinate
system origin. (Or am I burbling again? :-) )

I don;t think the words scalar or vector are very useful to describe
longitude or latitude.

A scalar is a physical quantity that can be described by a
single real value.

A position on the Earth's surface requires two coordinates, and
thus is a vector quantity.

I wondered about how rigorous I was being, in classing lat and
long as vectors, then twigged each is WRT an origin. Each, in
effect, defines a distance in a particular direction. It just
happens to be working in spherical coordinates, as I said. So
"lat" is a distance north/south of the equator, with east/west
partner distance undefined. Analogously for "long".

If you need a distance, measurable by a ruler, consider we are
talking of a spheroid with a known, albeit variable (depending
on the lat+long), radius. But distances can just be angular.

The usefulness of spherical geometry vectors of course depends
on the task in hand and it may actually be easier to use other
mental models. But IMHO there's a good case to be made here.

It probably comes down to one's philosophical outlook and I am
not planning to waste (more) time arguing _that_ (again). :-)
--
Andrew Stephenson

.

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