[OSRS-PROJ] Roussilhe Oblique Stereographic

werchowyna at pf.pl werchowyna at pf.pl
Thu Mar 11 17:25:11 EST 2004

I changed the order of our conversation slightly to make it more readable

> > > 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.
> 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>
> Same script for sterea.

When I try to use the "stere" projection in my Grass 5.0.3 it asks for the
"Latitude of True Scale [lat_ts]".
And you don't provide this parameter in your example script. How come?
Besides this [lat_ts] is the only one input I don't know for mymap.
And you give the x_0 and y_0 while my Grass doesn't ask for them. What's
(Should I send you the step by step listing of the Grass' interface during
the "stere" projection application?)

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

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

I thought Grass has been utililizing the libproj4 permanently. Or am I
wrong? If I'm not then I could install the 'fixed' libproj4 and be happy.

for example here comes the info.txt from the libproj0-4.4.7-1mdk.i586.rpm
installed on my Mandrake 9.2 with Grass 5.03:
NAME:         libproj0
VERSION:      4.4.7
RELEASE:      1mdk
SUMMARY:      Cartographic projection software - Libraries
DISTRIBUTION: Mandrake Linux
VENDOR:       MandrakeSoft
PACKAGER:     Buchan Milne <bgmilne at linux-mandrake.com>
GROUP:        System/Libraries
OS:           linux
ARCH:         i586
SOURCE RPM:   proj-4.4.7-1mdk.src.rpm
Cartographic projection software and libraries.

dated 07.08.2003
you can find it at any Mandrake ftp in Contrib

> > 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.

They are in Chineese remember! I'll send them to you within 24 hours.

> 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.

So if there will be a need to talk to someone talking the universal language
I'll try to stick you together with the guy.


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