[Proj] datum matters

strebe strebe at aol.com
Sat Mar 28 23:28:35 EST 2009

On Mar 28, 2009, at 5:09:36 PM, "Richard Greenwood" <richard.greenwood at gmail.com> wrote:
In this era we must think in terms coordinate systems, not just
projections, despite the name of the list and library. I’m using
“coordinate system” as a projection + datum, or lat/long + datum. To
tie a position to the earth you need both. Many users, both C
programmers incorporating the library in their own work, and end users
accessing the library thru the various OSGEO stack applications that
use the library, do not distinguish between a “projection” and a
“coordinate system”.
This notion of having to think in terms of coordinate systems, not just projections, is only true within some domains. Large-scale maps? Yes. Medium and especially small-scale maps? No. Analysis of projection distortion? No. Believe it or not, a LOT of medium and small-scale maps are made. People tend to view the world through their own myopic interests.

Gerald Evenden and I do not agree on many things, as the years have demonstrated, and I certainly do not understand flouncing off in a huff over something so obscure. Still, I do think it is more reasonable to keep projections and coordinate systems distinct than it is to conflate them. They ARE distinct. Perhaps we save some people from their own ignorance by insisting on an integration of the two, but then we impose a computational and conceptual burden upon those who don't need them, as well as encourage those who do need them to confuse themselves into believing their own interests are the norm.

— daan Strebe
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