[Proj] Re: Comments of tmerc, etmerc and ftmerc errors

strebe strebe at aol.com
Sat Jun 14 00:37:07 EDT 2008

On Jun 13, 2008, at 2:56:35 PM, "Gerald I. Evenden" <geraldi.evenden at gmail.com> wrote:
My sentense had nothing to do with area and by Cartesian usage I was denoting 
measuring distances, azumuths, etc. from the Cartesian data and it certainly 
seems that scale error greatly affects these measurements.
Yes. Scale error greatly affects those measurements... but you're not going to get any better results with equal-area maps for those measurements than you will from conformal. That is because the "scale error" is just as pronounced in equal-area maps as it is in conformal maps. Hence...

"Extended geographic range usage of any conformal projection is a contentious issue as any resultant grid system has sufficiently large scale errors as to make the Cartesian usage of the grid very questionable."

...does not follow. The only clearly improved measurement you'll get from equal-area maps is measurement of, well, area. You'll generally find approximations of azimuths to be much easier on conformal maps than equal-area. Distances are a mess on conformal or equal-area either one.

-- daan Strebe
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