[Proj] Transverse Mercator algorithm
Gerald I. Evenden
geraldi.evenden at gmail.com
Sun Sep 7 16:29:16 EDT 2008
On Sunday 07 September 2008 2:53:23 pm Charles Karney wrote:
> > I will get a 3D plot made sometime today.
> There's a good chance that this will look messy because of the
> oscillatory behavior of the error with latitude and the fact that
> round-off errors dominate for small x.
On the contrary. The error well out of the lon,lat=90,0 zone is simply a
frothy quantum like noise around 10^-9 meters due to float precision limits.
As one approaches 90,0 the surface is a remarkable smooth---totally without
undulations. Iso-error contours are nearly circular with the center at 90,0
on an equirectangular grid.
Give it a looksee:
As to generating a zillion test points, I had a gaming break while waiting for
just 2116 or so points. It takes nearly a second per point for starters and
more as one nears upper limits. With your original loops of 10 points per
degree I figure maybe:
900*900=810000 points at 2/second gives 6750 minutes or 112 hours or a little
more than 4 1/2 days. And that is with my klutzy 3GHz 64 bitter.
A few more points than I have patience for. ;-)
The whole religious complexion of the modern world is due
to the absence from Jerusalem of a lunatic asylum.
-- Havelock Ellis (1859-1939) British psychologist
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