[Proj] Re: Newbie Polar stereographic question

[Gerald I. Evenden]

On Thursday 13 July 2006 11:23 am, Oscar van Vlijmen wrote:
> I wonder, can all 3 variants of the EPSG (OGP) stereographic projections be
> calculated with (lib)proj's stere?

+proj=stere is probably OK for most polar aspects.  However, most non-US 
oblique stereographic projections probably use +proj=sterea.  I am not sure 
about equitorial needs as the problem does not seem to come up very often.

BTW, my previous statement about the projection ray trace is not true for the 
oblique, elliptical stereographic because the normal to the projection plane 
at the point of tangency to the *ellipse* does *not* pass through the center 
of the earth.  It only passes through the center for all cases of the sphere 
and only the polar and equitorial cases of the ellipsoid.

> EPSG coordinate operation method 9810:
> Polar Stereographic (variant A)
> For Projected Coordinate Reference System: WGS 84 / UPS North
>
> EPSG coordinate operation method 9829:
> Polar Stereographic (variant B)
> For Projected Coordinate Reference System: WGS 84 / Australian Antarctic
> Polar Stereographic
>
> EPSG coordinate operation method 9830:
> Polar Stereographic (variant C)
> For Projected Coordinate Reference System: Petrels 1972 / Terre Adelie
> Polar Stereographic
>
> Especially variants B and C still puzzle me a bit - in the sense of how to
> do it with PROJ?
>
> Probably not possible; the PROJ file "epsg" tells me for instance:
> # Petrels 1972 / Terre Adelie Polar Stereographic
> # Unable to translate coordinate system into PROJ.4 format.
>
> Formulae and numerical examples can be found in the EPSG/OGP Guidance Note
> 7-2.

-- 
Jerry and the low-riders: Daisy Mae and Joshua
"Cogito cogito ergo cogito sum"
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