[GRASSLIST:4338] Re: GIS visitor requests directions

Victor Wren vwren at timension.com
Tue Aug 20 13:27:33 EDT 2002

On Mon, Aug 19, 2002 at 07:21:56PM -0700, Eric G. Miller wrote:
> On Tue, Aug 20, 2002 at 01:36:37AM +0100, Glynn Clements wrote:
> > 
> > Nigel McFarlane wrote:
> > 
> > > > > As I understand this (based on the man pages and experimentation)
> > > > > this ONLY works when projecting between NAD27 and NAD83.
> Also, GRASS doesn't
> not handle State Plane 83 without some extra effort (that is, the
> g.setproj routine does not offer state plane 83 as an option, so
> "state plane" is always state plane 27 in it's "mind").

Ah, so!  This is very useful information.  I did not get any complaint
from it when I used State Plane projection with NAD83 (as I got when
I stupidly tried to combine the GRS80 ellipsoid and NAD27).

> Probably
> better to just get hold of the projection parameters for the AOI and
> plug them in (then adjust ft. vs. US ft. to meters conversion, if using
> survey feet).  With Roger's "fix", the NAD27 <-> NAD83 should be handled
> well enough (using NADCON the error should be pretty low).

This is getting a little over my head, now.  I have not tried to add new 
projections to GRASS before.  Is there anywhere instructions to do this is
recorded on the web?

Victor Wren (vwren at timension.com)

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