[Proj] gaus-kruger projection[Scanned]

[Pieter Bosch]

Thanks for your replay

Well I'm generating maps for the African continent with
spheroid/ellipsoid wgs84 and a datum called "Hartebeesthoek 94".  UTM
gridzone 34 is one that I will be using  -> is there a dif between gauss
zones and Utm zones?

What do you mean with "what instance of the Gauss-Kruger projection" ?
give me a example of a instance of the Gauss-Kruger projection. Pls

An example of my values 

CM =23 deg East
Datum = hartebeesthoek 94 
Ellipsoid = wgs84
UTM zone= 34J
Lat To convert= -28
Long to convert=23

As I understand (correct me if I'm wrong) there is a Lambert
Conformal(preserves the areas-I think) projection and a Gauss projection
(preserves the angles). Both of them are Transverse Mercator projections
(or a form of it) . the one is based on spherical and the latter is
based on ellipsoidal shape of the earth. So how will I know if I'm
actually using the Gauss projection . Is using wgs84(a ellipsoidal)
enough to secure this.

-----Original Message-----
From: Mikael Rittri [mailto:Mikael.Rittri at carmenta.com] 
Sent: 06 February 2009 12:07 PM
To: PROJ.4 and general Projections Discussions
Cc: Pieter Bosch
Subject: RE: [Proj] gaus-kruger projection[Scanned]

There is no need to recompile proj.4. Gauss was a very productive guy. 
I don't think the pj_gauss.c has anything at all to do with Gauss-Kruger

projection.

My answer is: 

The projection method that is usually called "Gauss-Kruger" in 
Europe (and Asia?), is the same as the one that is usually called 
"Transverse Mercator" in USA. 

(There are also some slightly different projection methods, that should 
 have the right to be called "a kind of Transverse Mercator", but which 
 differ from Gauss-Kruger.  For example, Gauss-Schreiber.  They are 
 discussed on this list now and then, but I don't think you need them.) 

So, just use

    +proj=tmerc 

to implement what you call Gauss-Kruger. 

Pieter Bosch wrote: 
> if so, what is the parameters to use. 

If you mean the names of the parameters, they are the usual ones:

 +lat_0 // central latitude.  Often zero, but not always.
 +lon_0 // central longitude (for the central meridian).
 +k     // scale factor on the central meridian. 
 +x_0   // false easting
 +y_0   // false northing 
 +ellps // ellipsoid 
 +datum // datum (it is better to use +datum instead of +ellps, I think)

 +units // the length unit of projected coordinates
 +no_defs // I've never quite understood this one, sorry. 

I think x_0 and y_0 should normally be expressed in meters (because 
that's the length unit used for the predefined ellipsoids), even 
if +units specifies that projected coordinates are in feet, say. 

But, if you mean "what values of the parameters should I use", 
that would depend on what instance of the Gauss-Kruger projection 
that you want to implement.  You haven't told us that.  Do you have
a name for the Coordinate Reference System, or the country name and 
and a Gauss-Kruger zone number?

Best regards,
--
Mikael Rittri
Carmenta AB
SWEDEN
www.carmenta.com

-----Original Message-----
From: proj-bounces at lists.maptools.org
[mailto:proj-bounces at lists.maptools.org] On Behalf Of
support.mn at elisanet.fi
Sent: den 6 februari 2009 09:59
To: PROJ.4 and general Projections Discussions
Subject: Re: [Proj] gaus-kruger projection

Hello,

I would swap the pj_tmerc.c (or what it is) to pj_gauss.c and compile it
again.

It may need some additional fixing in some init areas... ??

Regards: Janne.

---------------------------------------------------

Pieter Bosch [pieter.bosch at za.saabgroup.com] kirjoitti: 
>  
> 
> Hi,
> 
>  
> 
> Does anyone know if proj4's  command prompt app can do gaus-kruger 
> projection and if so what is the parameters to use. How would the 
> following statement have to change to be in Gaus-kruger.
> 
> +proj=tmerc +ellps=WGS84 +lon_0=12 +x_0=500000
> 
>  
> 
> I've seen a pj_gauss.C file  but I cant see any abbreviation in the 
> projection list that identifies GAUSS-Kruger. Please help
> 
>  
> 
> Cheers
> 
> pieter
> 
> 
> _______________________________________________
> Proj mailing list
> Proj at lists.maptools.org
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