[GRASSLIST:2567] Re: Multiple UTM zones

Glynn Clements glynn.clements at virgin.net
Mon Oct 8 12:58:52 EDT 2001

Rich Shepard wrote:

>   What is the standard (or recommended) protocol when a project area falls
> across the boundary of two UTM zones? Are values from one reprojected onto
> the other? Is this a non-issue? I'm moving to UTM for the projection of
> choice rather than State Plane Coordinates or Lambert Conformal Conic.

UTM isn't really "a projection"; it's a family of 60 projections. For
the most part, GRASS won't care if you don't use the "right" zone
(beyond the fact that the distortion increases as you get further from
the tangent meridian).

Actually, GRASS doesn't really deal with projections. Most programs
just operate upon abstract 2D coordinates, treating the region as if
it were flat.

To get down to specifics: if you have data from several zones, and
want to import it into a single location, you will probably need to

a) convert the coordinates using m.proj, or

b) import the data into zone-specific locations then re-project it
into the composite location using [rvs].proj.

Glynn Clements <glynn.clements at virgin.net>

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