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| GeoCommunity Mailing List |
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| Mailing List Archives |
| Subject: | Re: GISList: Regional GIS |
| Date: |
06/09/2003 07:45:01 PM |
| From: |
Paul Ramsey |
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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!
>
>
>
>
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Paul Ramsey
Refractions Research
Email: pramsey@refractions.net
Phone: (250) 885-0632
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________________________________________________________________________
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