[GRASSLIST:5075] Re: v.proj datum errors

Eric G. Miller egm2 at jps.net
Mon Nov 25 22:21:28 EST 2002

On Mon, Nov 25, 2002 at 04:01:37PM -0700, Richard Greenwood wrote:
> GRASS 5.0.0 pre4 (and probably earlier) was "hardwired" to read the state27 
> definitions when you created a new location. I don't know if this has been 
> fixed. Eric Miller suggested renaming you grass5/etc/state27 file and the 
> creating a symbolic link to the state27->state83 so that when you created a 
> new location it would read the values from state83. So you might look in 
> your PROJ_INFO files and see what values got used.

Yes g.setproj is still hardwired for state27.  I'm currently in
dereliction of duty, as I've promised to fix the projection handling in
GRASS be more correct and transparent (and handle datums properly)...

> Also - I don't think datum transformations are supported. Somebody please 
> correct me if I'm wrong. In my area (western wyoming) there is only about 1 
> second of rotation between NAD27 and NAD83 so I have been able to manually 
> edit the headers for raster files and get a workable datum conversion for a 
> small area (a DRG).

NADCON nad27<->nad83 support was added to [rsv].proj.  They should spew
some messages about the transform.  Otherwise, datum transforms are not
support in 5.0.

"...the plural of anecdote is [not?] data."  - attrib. to George Stigler

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