[OSRS-PROJ] gauss-krueger/transverse mercator

[Gerald I. Evenden]

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= ???

+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.

As for "unfact" I have absolutely *no* idea what that is.

Also see imbedded note below.

__________________________________________________
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 4:40 PM
Subject: Re: [OSRS-PROJ] gauss-krueger/transverse mercator


> Hi Andreas,
>
> maybe not an answer for your question, but of general
> (European) interest: I convert with following calls:
>
> Rechtswert Hochwert -> Lat Long
>
> proj -I +proj=tmerc +a=6377397.1550000003 +es=0.0066743720\
>   +lat_0=0.0000000000 +lon_0=$bezug +k=1.0000000000 +x_0=$ans
+unfact=1.0000000000
>
> where $bezug=meridian (degree, example: 9)
> and   $ans= False Easting (example: 3500000)
>
> Example:
> In:  3560000 5700000
> Out: 9d51'46.414"E   51d25'57.97"N
>
> -------------------------------
> Reverse transformation:
> Lat Long -> Hochwert Rechtswert (y x)
>
> proj +proj=tmerc +a=6377397.1550000003 +es=0.0066743720
+lat_0=0.0000000000\
>      +lon_0=$bezug +k=1.0000000000 +x_0=$ans +unfact=1.0000000000
>
> where $bezug=meridian (degree, example: 9)
> and   $ans= False Easting (example: 3500000)
>
> Example:
>
> In:  9d51'46.414"E   51d25'57.97"N
> Out: 3560000.01      5699999.99
>
> Using your example I get (note: reverse order):
> 10.5W 29.27N
> 1585979.82      3402162.10

!!NOTE: you are about 20 degrees west of the CM with the above
longitude.  A tad out of range of the projection.

> I am not shure if it is defined in southern hemisphere (but why
> not, at least numerically)?
>
> Best wishes
>    Markus
    ...

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