[GRASS-user] help needed with polar projections

[Henning Lorenz]

Hi Daniel!

You have specified your region in longitude/latitude while you work in
Polar Stereographic Projection whose coordinate system has "meters" as
unit. You have to convert your lat/long values first, and don't
forget to set the resolution to a proper value!

Henning

On Thu, 11 Jan 2007 13:24:24 -0500, Daniel.Gillespie wrote:

> Hello:
> 
> I am new Grass user, and am having some problems trying to set up a
> polar projection.  I am using Grass 6.0.2 that I compiled, and am
> working on a RedHat Linux system.
> 
> I have tried to set up a Universal Polar Stereographic (UPS) projection,
> as well as an Antarctic Polar Stereographic projection.  The UPS
> projection did not appear to work at all.  The Antartic Polar
> Stereographic projection didn't fail, but when I reproject a vector file
> with Antarctica, the results are not what I expected.  I think that I
> may have set the default region incorrectly, because only a small
> portion of Antarctica appears in the monitor.  The details of the
> projections and region follow below.
> 
> Any suggestions for how to set up a UPS projection or other polar
> projections, or how to define the region setting properly for the
> Antarctic polar projection would be much appreciated!
> 
> Many thanks,
> 
> Dan Gillespie
> 
> ..................................
> 
> Here are the projection parameters for the 2 locations:
> 
> 
> UPS 
> 	GRASS 6.0.2 (SouthPole2):~ >  g.proj -w
> 	WARNING: OGR can't parse PROJ.4-style parameter string:
>         	 +proj=ups +south +a=6378137 +rf=298.257223563 +no_defs
>          	 +towgs84=0.000,0.000,0.000 +to_meter=1.0000000000
>          	 (OGR Error code was 5)
> 	WARNING: g.proj: Unable to convert to WKT
> 
> 
> Antarctic Polar Stereographic
> 	GRASS 6.0.2 (SouthPole4):~ > g.proj -w
> 	PROJCS["Stereographic",
>     	   GEOGCS["wgs84",
>               DATUM["unknown",
>                   SPHEROID["wgs84",6378137,298.257223563]],
>               PRIMEM["Greenwich",0],
>               UNIT["degree",0.0174532925199433]],
>     	PROJECTION["Polar_Stereographic"],
>     	PARAMETER["latitude_of_origin",-71],
>     	PARAMETER["central_meridian",70],
>     	PARAMETER["scale_factor",1],
>     	PARAMETER["false_easting",0],
>     	PARAMETER["false_northing",0],
>     	UNIT["meters",1]]
> 	
> 	Here is the default region for this location:
> 	N: 0
> 	S: -90
> 	W: -180
> 	E: 180
> 	grid resolution NS:  1
> 			EW:  1
> 	rows: 90
> 	columns: 360
> 
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