[OSRS-PROJ] gauss-krueger/transverse mercator

[Markus Neteler]

[cc to Morten Hulden morten at ngb.se]

On Mon, Jun 12, 2000 at 08:42:02PM -0400, Gerald I. Evenden wrote:
> +k rather than the preferred +k_0 may be an artifact that I left in the USGS
> distribution.  I will have to check.
Yes, perhaps:

more PROJ.4/CHANGE-LOG 
Rel. 4.1 93/3/8 Base-line --- @(#)CHANGE-LOG    4.14 95/09/23 GIE REL
-------------------------------------------------------------------------
93/3/20
        pj_init -- added +k_0 as alternative to +k so as to match
        documentation.
[...]
 
> The "+unfact" option *is not* of my doing and comes from some non-USGS
> distribution.  I'm mystified and curious of its purpose.

The file src/libes/get_proj.c (in GRASS) was developed by CERL
long time ago and added to the PROJ4 directory. It provides some
functions for GRASS to use the PROJ4 routines directly instead
of calling the "proj" in a script mode.
There are three functions provided:

int pj_get_kv(info, in_proj_keys, in_units_keys)
int pj_get_string(info, str)
int pj_zero_proj(info)

You can access the current file directly to look at it:
http://freegis.org/cgi-bin/cvsweb.cgi/~checkout~/grass/src/libes/proj/get_proj.c


The software used in GRASS 5 is:
    -------------------- P R O J . 4 --------------------
                      @(#)README        4.11 95/09/24 GIE REL"
This is Release 4.3 of cartographic projection software.

The software used in GRASS 4.x was PROJ4.2.


> Since I see "m." I suppose it is a product of the GRASS people.
The m.proj is a GRASS module to control the PROJ4 software.
The GRASS 5 version always outputs the command line calling the
"proj" tool. There I got the string I posted yesterday to convert
Gauss-Krueger to Lat/Long and reverse.

> As some may be unaware, I authored the original PROJ.4 as distributed
> by the USGS kai.er.usgs.gov site.
We are grateful to your for your distribution of PROJ4.

Please note that the unchanged PROJ4 was included in GRASS.
>From the GRASS sources it reads:
src/libes/proj/README 

This is PROJ4.3.3 from kai.er.usgs.edu

Added in GRASS 5 beta4d (16. Sept. 1999)

--------
Morten, could you please teach me/us about "unfact" parameter?
I shall store it somewhere in GRASS sources.

Kind regards

 Markus Neteler
 
> __________________________________________________
> Jerry Evenden and the Low Riders, Katie and  Daisy May
> gevenden at capecod.net  http://www.capecod.net/~gevenden
> ----- Original Message -----
> From: Markus Neteler <neteler at geog.uni-hannover.de>
> To: <osrs-proj at remotesensing.org>
> Sent: Monday, June 12, 2000 6:49 PM
> Subject: Re: [OSRS-PROJ] gauss-krueger/transverse mercator
> 
> 
> > On Mon, Jun 12, 2000 at 05:48:24PM -0400, Gerald I. Evenden wrote:
> > > A couple of elements caught my eye here and represent modifications
> > > to PROJ.4 that are not part of the USGS distribution.  I am curious
> > > as to what the parameter definitions are:
> > >
> > > +unfact= ???
> >
> > This is queried in
> > proj4/get_proj.c
> >
> > > +k= ???
> > >
> > > "k" is terminology for the scale factor anywhere while k_0 refers to
> > > a scale factor at a specific location.  I don't think dropping the _0
> wise
> > > or meaningful.
> > I guess it is the scale factor as being 0.99996 for UTM and 1.0 for
> > Gauss-Krueger.
> >
> > > As for "unfact" I have absolutely *no* idea what that is.
> > This I cannot recall, but was told it once when wondering about it.
> > Sorry - no help today...
> >
> > Morten Hulden <morten at ngb.se>, who updated the m.proj of GRASS 5,
> > explained it to me last year.
> >
> > Sorry to be no more help (but proj4 and m.proj work well!)
> >
> >  Markus Neteler
> 
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-- 
Dipl.-Geogr. Markus Neteler *  University of Hannover
Institute of Physical Geography and Landscape Ecology
Schneiderberg 50 * D-30167 Hannover * Germany
Tel: ++49-(0)511-762-4494  Fax: -3984
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