On Mon, Aug 04, 2003 at 07:25:09PM -0500, Richard Rauch wrote:
> Anyway, I thought that when the terms "longitude" and "lattitude" were
> used, one was always refering to the "traditional" system (someplace
> in Greenwich at longitude 0, the equator at lattitude 0; I don't know
> where they place the center of the earth for defining angles phi & theta).
> Sorry for assuming that that was clear.

AFAIK, Greenwich is longitude 0 and the equator is latitude 0 in all
systems; the difference between the various systems is more subtle
than that. The earth isn't a sphere; it's obviously quite irregular :)
However, an ellipsoid is a pretty decent approximation... the
differences lie in exactly which ellipsoid to pick.

In any case, as others have mentioned, while the differences are
important to some people, it doesn't matter for this application... I
don't think it'll make a pixel of difference on any maps, and if some
stalker's gonna drive to your place, they won't care if they're off by
a couple of meters :)

FWIW, the NAD27 ellipsoid (Clarke 1866) is:
semiminor axis 6356584 meters, eccentricity^2 0.006768658.
WGS84 is:
semiminor axis 6356752 meters, eccentricity^2 0.006694380.
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