g.setproj

[Anne Gisiger]

Quinn Hart wrote:
> 
> Can someone explain how g.setproj works.  According to the man page, it
> should prompt for the projection.  In practice howver, it seems to read
> the proj from DEFAULT_WIND.  The problem I'm finding is that the only
> valid proj: values are:
> 	0:(xy)
> 	1:(utm)
> 	2:(state plane)
> 	3:(ll)
> and g.setproj doesn't like anything else.  So how do I get nifty
> projections like aea,lcc,merc,tmerc?  Note this is the same list that
> comes up for me when making a new location.  Shouldn't that include all these
> projections?
> 
> Thanks in advance.
> 
> 
> Quinn Hart  (qjhart at ucdavis.edu)
> Dept. Land, Air, and Water Resources
> UC Davis
> 
> 

Hello Quinn
 
You do not need g.setproj to create a new location in a projection other than
the GRASS defaults. 
Actually, if you create a new location and the files PROJ_INFO and PROJ_UNITS
directly you can use all the projections supported by the software PROJ and
MAPGEN!! I think that more than 60 different projections are currently
available. The advantage is that although all GRASS modules do not recognize 
these projections, v.proj does, so you can easily import/export vector data.
I have been using the Lambert Azimuthal Equal Area proj for the last two years,
and never enountered any major problems.

About the aea,lcc,merc,tmerc projections, GRASS accepts them when you create 
a new location while getting into GRASS. I have never tried g.setproj since 
PROJ_INFO and PROJ_UNITS must be created by hand for non-standard projs.
 
You should also check which version of GRASS you are using since version 4.1
deals with projection in a different manner than 4.0.
 
Do not hesitate to contact me, if you need more help.

-- 
Anne Gisiger                                     FAX: (501) 575-3846
CAST, Center for Advanced Spatial Technologies   TEL: (501) 575-6159     
12 Ozark Hall, University of Arkansas         
Fayetteville AR 72701                             anne at cast.uark.edu