[OSRS-PROJ] Roussilhe Oblique Stereographic

[Gerald Evenden]

See imbedded comments below
On Mar 10, 2004, at 7:04 PM, <werchowyna at pf.pl> wrote:

>> I would rather deal with an article in French rather than Polish (no
>> offense to the Poles,  please)
> I'm not that touchy :)
> I have met few Germans and Americans try speak Polish
> maybe it wasn't Chineese but it wasn't Polish either
>
>> For printed references readily available there is:
>> 1) Bugayevskiy, Snyder p. 169, and two versions in 2) Yang, Snyder and
>> Tobler pp. 19--21,  3)pp 166-168.
> Where to look for them?

Sorry, I was being *Very* brief in my bibios:

Map Projection Transformation, 2000, Oihe Yang, JP Snyder and Tobler

Map Projections---A Reference Manual, 1995, Lev M Bugayevskiy & JP 
Snyder.

Both are available at Amazon.com.

>> As for latitude of true scale, this is usually only used in the polar
>> version.  k_0 is more appropriate for oblique and equatorial.
> So it seems that the libproj4's "Stereographic" projection is not 
> suitable
> here because it demands the "latitude of true scale". HOW DO YOU 
> THINK? This
> projection requires the k_0 "scale factor" too. This is not a problem 
> - I
> know the k_0 for all the "Uklad 1965" zones. But the definition of 
> "Uklad
> 1965" doesn't mention such a parameter as the "LATITUDE OF TRUE SCALE" 
> at
> all.

+proj=stere uses +k_0 in oblique case (+lat_0 .ne. 90)

There is also +sterea (alternate stereographic in the libproj4 system.


>> 1 and 2 my be similar but 3 is based on a transfer through 
>> Gauss-Kruger.
>> Interestingly, the Polish web paper I picked up gave a version that
>> looks similar to 3.  With the Polish paper I think I could do a 
>> complete
>> version (forward-inverse).
> To make things clear:
> The 1965 System we are talking about consists of 5 zones, where four 
> are in
> Roussilhe and one is Transverse Mercator.
> The Mercator one (5th zone) is not obscure at all and easily 
> applicable in
> Grass.
> Those 1-4 Roussilhe ones are not obscure as well but I don't know how 
> to
> apply them into Grass.

Yes, I figured that from the Polish web site.  That part was pretty 
clear.

If I was using the PROJ4 system I would key the first zone as follows:

+proj=stere +lat_0=50d37'30 +lon_0=21d5' +x_0=5467000 +y_0=4637000
    +k_0=0.9998 +<ellipsoid parameters>

GRASS used PROJ a long time ago but I lost contact somewhat before
CERL stopped support.

Same script for sterea.

> I have some literature (doc and pdf) regarding "Uklad 1965" besides the
> http://www.atomnet.pl/~geodeta/2000/59text1.htm .
> They contain plenty of formulas which I don't get at all (I'm not
> a cartographer or geodet or whatsoever). If you would like to have a 
> look at
> them I would send them to you and would assist you in trying to 
> understand
> Chineese with pleasure. Besides - I know one Polish amateur 
> cartographer/GPS
> fan who would help. He speaks English well so you coud try to consult 
> him
> too.

I would love to see it.  My main concern is that the material 
represents the
method used in "official" Polish applications.  I say this because I 
seem see at least
two different methods and wonder which one is the "real" one.

As I said, I think I could do a PROJ.4 version from the web site data 
as long
as I had someone to answer a few questions that may come up.  The 
language
of mathematics is pretty universal.

Also, "benchmark" values are also of *great* assistance:  That is know 
values
of  lat-lon == x-y.

But even if I get a successful process on libproj4, how does this help 
you
with your GRASS effort?

> Maciek Sieczka
>
>
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_____________________________________
Jerry and the low riders: Daisy Mae and Joshua

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