[Proj] proj4 string for perfect sphere

[Mikael Rittri]

Janne wrote:

> 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. 

Regards,
Mikael Rittri
Carmenta
Sweden
http://www.carmenta.com

-----Original Message-----
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

Hello,

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 ;)

regards: Janne.


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