[gradsusr] Better polygon shapefiles

[Michael Mase]

Thanks! I might dig into this further to see if I can find a series of
steps to mitigate this. Will update if I find anything.

On Mon, Jan 18, 2016 at 5:44 PM Jennifer M Adams <jadams21 at gmu.edu> wrote:

> On Jan 18, 2016, at 3:56 PM, Michael Mase <masester at gmail.com> wrote:
>
> Thanks, Jennifer! This is very helpful. I'm interested to learn more why
> GrADS can't export with rings.
>
> http://cola.gmu.edu/grads/gadoc/shapefiles.html#caveat
> —Jennifer
>
>
>
> I've used degrib a few times and it seems to do this beautifully. However,
> it relies on the GRIB data being in the final state - which makes GrADS
> more appealing.
> On Mon, Jan 18, 2016 at 3:52 PM Jennifer M Adams <jadams21 at gmu.edu> wrote:
>
>> The polygons in a Grads-generated shapefile conform to the ESRI
>> specifications (
>> https://www.esri.com/library/whitepapers/pdfs/shapefile.pdf) but have an
>> additional constraint so that GrADS will render them properly: no rings,
>> a.k.a. polygons within other polygons, a.k.a. “donuts". For this reason,
>> the filled contours are are sliced up into odd-looking polygons that you
>> can see clearly if you draw them individually, or with an outline color
>> that does not match the fill color. There is nothing to be done about that
>> on the GrADS side. There are probably some GIS tools that will merge
>> polygons, but if you want a smooth-looking and outlined filled contour
>> plot, write out the polygons and line contours into two separate shapefiles
>> and overlay them. —Jennifer
>>
>>
>> On Jan 18, 2016, at 2:08 PM, Michael Mase <masester at gmail.com> wrote:
>>
>> Exporting shapefiles works fantastic when using lines. However, when you
>> export using polygons, you get very broken and disconnected shapes
>>
>>
>> Does anyone have any advice on writing/exporting solid shapefiles that
>> have joined multi-polygons (for each contour region; each temperature
>> interval, for example)?
>>
>> It would be nice if each polygon layer represented each interval on the
>> map and was nicely joined and closed properly.
>>
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>>
>> --
>> Jennifer M. Adams
>> Center for Ocean-Land-Atmosphere Studies (COLA)
>> 111 Research Hall, Mail Stop 2B3
>> George Mason University
>> 4400 University Drive
>> Fairfax, VA 22030
>>
>>
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>
> --
> Jennifer M. Adams
> Center for Ocean-Land-Atmosphere Studies (COLA)
> 111 Research Hall, Mail Stop 2B3
> George Mason University
> 4400 University Drive
> Fairfax, VA 22030
>
>
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