[Proj] proj4 string for perfect sphere
Mikael.Rittri at carmenta.com
Tue Apr 17 06:12:45 EST 2012
> never leave the sphere (or ellipsoid) just keep doing all calculations
> there - it is much easier (you don't need projections)
"Much easier" are not the words I would use. "Much harder" fits
better. That's one reason projections are useful.
Spherical geometry isn't too bad for simple problems (distance,
azimuth etc.), but just think of point-in-polygon test, area of polygon,
and so on.
From: proj-bounces at lists.maptools.org [mailto:proj-bounces at lists.maptools.org] On Behalf Of support.mn at elisanet.fi
Sent: den 17 april 2012 11:54
To: PROJ.4 and general Projections Discussions
Subject: Re: [Proj] proj4 string for perfect sphere
Demitri Muna [thatsanicehatyouhave at me.com] kirjoitti:
> Hi Bob,
> Thanks very much for the extensive comments. The biggest thing I learned about GIS this week (starting from knowing nothing about it last week) is that calculations are primarily done on an XY plane which are projections of a curved surface. I had naively assumed going in that calculations and indices (e.g. spatialite) were optimized for the surface of a sphere.
A small notice for a beginner: If you want to stay accurate and avoid lots of trouble with projections generated errors never leave the sphere (or ellipsoid) just keep doing all calculations there - it is much easier (you don't need projections) and you will stay accurate for ever ;)
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