[OSRS-PROJ] Oblique Stereographic

Gerald I. Evenden gerald.evenden at verizon.net
Wed Mar 5 10:43:11 EST 2003

Like I said, there's are an infinite set of conformal solutions for
any basic type.  The request here was to solve the EPSG spec and that
one only.  As for Roussilhe and others, we'll cross those creeks when
we get there.  At least I have source equations for Roussilhe.

Point me to source material on the Bulgarian/Romanian projections and
I'll be glad to consider them.  So far none of my material even
whispers those names.  BTW: Hristow is Germanization of V.K. Khristov
a Bulgarian geodesist. (from Snyder).  Romania remains the home
of the equally mysterious Transylvanian Alps.

Of course, the Gauss transformation is aged.  What is amazing to me
is that outside of brief mention of it, its application is *not* well
discussed in any of the well known cartographic projection books.
Oft criticized Pearson was the only source of basic info on this
method and even his was not complete.

If the EPSG people would do just a modicum of work on these
projections they would recognize the similarities between Krovak
and the stereographic and thus make documentation similar.  As it
stands now, Guide 7 again presents a muddled set of equations
probably stripped from some obscure bureaucratic memorandum written
by someone reinventing the wheel.  I'm at least trying to put
some shiny hub caps on the wheels.

On Tue, 2003-03-04 at 22:55, Clifford J Mugnier wrote:
> That mathematical routine only applies to the Oblique Stereographic Double
> (per the Canadian Maritime Provinces, such as Prince Edward Island).  I
> believe the French Navy Roussilhe Oblique Stereographic is different, and I
> know the Bulgarian Hristow Oblique Stereographic is quite different.  A
> particular truncation of the Hristow is used for the "Romanian Stereo 70."
> Others exist.
> See "Zeitschriff fur Vermessungswessen," circa 1930s-1940s.
> In regard to the "new" projections, the "double" technique with the
> Gaussian (conformal) Sphere is about 100 years old ...
> Cliff Mugnier
> ---------------------------------------
> I think I make a statement earlier today that I was on a roll.
> Well as of this evening the forward for the alternate
> Oblique Stereographic checks with the EPSG bench mark.
> After checking with the general description from EPSG and one
> of Snyder's books, the projection looked like another variation
> on the work I did on Krovak.  So being a good thief I copied
> the Krovak over, replaced the conic with the spherical
> oblique stereographic from Snyder and ... .
> I think there might be a general routine here, like the oblique
> stuff in libproj that will do the conformal sphere transform and
> then call the spherical projection of your choice.  Hey, you folks
> can cook up a bunch of new projections and give them names of
> your choice.
> Time to pull the switch and get ready for the "Daily Show."

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