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| GeoCommunity Mailing List |
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| Mailing List Archives |
| Subject: | Re: GISList: Regional GIS |
| Date: |
06/09/2003 07:55:01 PM |
| From: |
evillige .. gmu.edu |
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The most appropriate solution depends on the orientation of your states. Are they more north south running (in which case using the UTM projection will be most accurate) or are they more east/west oriented ( in which cas the conic projections Albers or Lambert are most appropriate). If they are fairly compact than it is a toss-up
EV
----- Original Message -----
From: Paul Ramsey <pramsey@refractions.net>
Date: Monday, June 9, 2003 8:41 pm
Subject: Re: GISList: Regional GIS
> What are you going to *do* with the data, is the determining
> question.
> Simply using the central UTM zone is the most convenient solution.
>
> However you will get distortions in distance and area measurements
>
> outside the bounds of the actual chosen zone. If you aren't doing
> any
> spatial analysis of distances or areas, then you are home free. If
> you
> are doing analysis, you might want to simply use your own
> projection, a
> custom parameterization of a standard projection like Albers Equal
> Area
> or Lambert Conformal Conic. Put your origin at the middle, your
> standard parallels around the top and bottom and supply some
> offsets to
> keep everything positive. Voila, instant projection! You will also
> get
> the best analytical results this way. The downside is that people
> tend
> to be bound to particular systems and often find arbitrary
> parameterizations confusing.
>
> On Monday, June 9, 2003, at 04:01 PM, epoulsen wrote:
>
> > Hello all!
> >
> > I am looking for some ideas on projections for a regional
> system. I am
> > looking to develop a regional data set that would encompass
> several
> > states
> > in the North East. I'd like to have the data from the states
> operate
> > as
> > seamless layers. I understand that the majority of governmental
>
> > agencies
> > prefer the state plane coordinate system for state data, but
> this will
> > not
> > work for seamless layers. I am leaning towards using UTM and
> while the
> > states are located within 3, I am leaning to using the zone in
> the
> > center
> > which encompasses the vast majority of the area.
> >
> > I was looking for your thoughts and especially any other
> examples of
> > regional systems over several states and how the projection
> issue was
> > handled.
> >
> > Thank you!
> >
> >
> >
> >
> > To unsubscribe, write to gislist-unsubscribe@geocomm.com
> >
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> >
> Paul Ramsey
> Refractions Research
> Email: pramsey@refractions.net
> Phone: (250) 885-0632
>
>
>
> To unsubscribe, write to gislist-unsubscribe@geocomm.com
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________________________________________________________________________
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