Map Projections

[Jill Schuler]

>From: "R.A.Sanderson" <R.A.Sanderson at newcastle.ac.uk>

>Is there a simple way of using two map projections simultaneously in GRASS?
> I have a GRASS location in UTM, but need to add new maps by digitising
>from base maps stored as latitude-longitude.  The v.digit command only
>seems able to cope with digitising using the same projection as the
>original location (in this case UTM). I could resort to using Arc/Info for
>digitising, then PROJECT/TRANSFORM into UTM before exporting to GRASS, but
>I'd prefer to carry out the whole operation in GRASS if possible.

Yes, use the v.proj command to project your utm location to lat/long

Usage:
 v.proj map=name [out=name] inloc=name [dbase=name] [set=name]
 
Parameters:
    map   input vector file name
    out   output vector file name
  inloc   Location containing INput vector map
  dbase   Database containing INput location
    set   mapset containing INput vector map

You can also use v.proj to shift your datum from nad27 to nad83.  Just 
create a file called DATUM_INFO under your PERMANENT mapset.  The file
contains 2 lines:

datum: nad27  or nad83
region: conus

v.proj is a contributed command under the src.contrib/SCS/mapdev/v.proj 
directory.

Jill
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Jill R. Schuler
USDA 
Natural Resource Conservation Service
2627 Redwing, Suite 120
Ft. Collins, Co 80526                     FAX: (970) 282-1930
					  VCOMM:9010-2418
e-mail: jschuler at itc.nrcs.usda.gov        Phone: (970) 282-2418