[OSRS-PROJ] Oblique Stereographic

[Clifford J Mugnier]

There's the Stereographic Double that is used in the Canadian Maritime
Provinces, like Prince Edward Island; there's the Roussilhe Stereographic
used by the French Armed forces, like in Syria and also in the Netherlands;
and there's the Hristow Stereographic that's used in Romania and various
other kinds of truncations of Hristow's series like in Poland and elsewhere
...

For more info on Hristow, see my past column on Bulgaria.  In English in
"PE&RS" and in Bulgarian in their national Journal of Geodesy.  Prof.
Hristow was quite a guy.

Cliff Mugnier
LOUISIANA STATE UNIVERSITY
----------------------------------
Folks,

I understand that there are (at least) two common forms of the Oblique
Stereographic projection.  In the Mentor Software system they are referred
to as the "International" version and the "Snyder" version.  It appears
that
the "proj=stere" used like this "+proj=stere +lat_0=34.2 +lon_0=39.15
+k=0.999534 +x_0=0 +y_0=0 +a=6378249.2 +b=6356515 +units=m" implements the
Snyder version.   I am wondering if there is a version of the
"international"
equations in PROJ.4 already?

The differences are on the order for 1 arcsecond for my test case ...
pretty
substantial.

PS. I believe I am assuming that coordinate systems such as "Deir ez Zor /
Levant Stereographic" listed in the EPSG database with method code 9809 are
the so the called International version.  The EPSG database gives the
equations for it's method, and notes that Snyder discussed a different
formulation that produces different results.

PPS. Anyone interested in implementing the EPSG equations if they haven't
already been incorporated into PROJ.4 under another name?

Best regards,

--
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam,
warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent


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