[OSRS-PROJ] Roussilhe Oblique Stereographic

[Clifford J Mugnier]

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
LOUISIANA STATE UNIVERSITY
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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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