[GRASSLIST:2177] Re: Projection questions

Frank Warmerdam warmerdam at pobox.com
Fri Jul 27 12:57:32 EDT 2001

Rich Shepard wrote:
>   I have a bunch of questions about the storage of information about mapset
> projections/coordinate systems/datum in GRASS-5. Let me start with a few.
>   1.) When I used r.in.gdal to import a DEM, the PROJ_UNITS file contains
> this:
> unit: unknown
> units: unknowns
> meter: 1


The "unit" value is the singular name for the linear unit.  The "units" value is
the plural.   The "meter:" value is the size of this unit in meters.  Since this
value is 1.0 we see that it is really in unit meters but r.in.gdal isn't 
establishing this correctly.

>   Can someone please interpret this for me? I assume that it means the units
> are meters, but why this syntax?
>   2.) Considering the same data set, the DEFAULT_WIND file contains:
> proj:       1
> zone:       11
> north:      4469934
> south:      4455924
> east:       404501.28124
> west:       393671.28124
> cols:       361
> rows:       467
> e-w resol:  30
> n-s resol:  30
>   I assume that "proj: 1" indicates UTM (because the PROJ_INFO file says
> so. But, where is the file that associates the number with the projection
> name? I've looked all through /usr/local/grass5/etc and the other
> directories there, but can't find it.

The association of 1 with UTM is "in the code", and not controlled by any
configuration files.  GRASS programs that report on projections should
know how to translate into human readable form. 

Best regards,

I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent

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