[OSM-dev] Good explanation of latitude-to-pixel conversion?

David MENTRE dmentre at linux-france.org
Sun May 25 14:59:30 BST 2008


Hello,

"Robert (Jamie) Munro" <rjmunro at arjam.net> writes:

> I don't understand. Why was it necessary?

According to the original poster, it improves the mapping by some 50
meters for some points, compared to projections made by a dedicated
software (proj4).

But I suppose all of this is quite subjective to the kind of projection
you are using and your purpose. And I'm certainly not a cartographer. :-)

> AFAICS, taking into account the variation of radius is *not* necessary,
> but can be done if you want to make the maths much harder for yourself.

The maths are not so difficult for Mercator projection but I agree are
more involved for other calculations. I have personally considered the
Earth a sphere when computing the distance between two points.

Sincerely yours,
david
-- 
GPG/PGP key: A3AD7A2A David MENTRE <dmentre at linux-france.org>
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