[OSRS-PROJ] Roussilhe Oblique Stereographic

Clifford J Mugnier cjmce at lsu.edu
Mon Mar 15 17:18:11 EST 2004

The ability of one algorithm to repeat a transformation within a certain
level of accuracy to another algorithm is a function of the distance from
the projection origin.

Your question is likely impossible to answer until both algorithms are at
hand and one does a "sensitivity analysis."  By that time, the question is
only academic anyway since you do have the exactly proper algorithm to
transform whatever it is at hand.

Cliff Mugnier
From: "Gerald Evenden" <gerald.evenden at verizon.net>
> Again, I want to make one point *perfectly* clear: there is no Roussilhe
> projection of any kind in *any* version of PROJ.
> The *only* stereographic projection in libproj4 (and earlier versions)
> is Snyder's which is basically a Gauss conversion to the sphere with
> some other scale tweeking and uses the spherical oblique stereographic
> projection.
What is the accuracy? I need circa 1m. Is it possible if I use the 'stere'
projection for Polish Roussilhe grid?

> I am working on that issue now and I will hopefully come up with
> two versions: one that is probably what Roussilhe first designed and
> a second that seems to be used by the Poles for their grid systems.
Do you need any help with the Polish papers?
Besides: I've got 2 *.xls calculators for GPS to "1965" grid conversion
based somewhat on Gauss-Kruger (I don't quite get it how). Maybe you could
make some use of them?

> When and if this material *ever* appears in GRASS software is a
> speculation far beyond my realm of knowledge.
Roger that.

Maciek Sieczka

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