[gradsusr] GrADS shapefile rings caveat

[Jennifer M Adams]

Hi, Mike — 
It is likely that the caveat will remain a feature in GrADS — even if we did not draw the inner rings, filling in the outer ring will always cover the entire area, and the area inside the inner rings could not be undrawn. A corrollary of the caveat is that shapefiles exported from GrADS will never have inner rings — the shading algorithm is specifically designed to avoid this problem. It would certainly have been easier to export closed contours as polygons with inner rings, but then GrADS would not have been able to display its own shapefiles properly. 

The workaround for the caveat is to rewrite the shapefile so that the polygons do not have inner rings; the boundary points would include the inner and outer rings with an overlapping line that connects the two rings. 
—Jennifer


> On Sep 15, 2017, at 11:10 AM, Michael Mase <masester at gmail.com> wrote:
> 
> Hi there,
> 
> Just wondering if the latest GrADS version supports exporting shapefiles with inner rings now or if there are plans to support this in the future?
> 
> Thanks,
> Mike
> _______________________________________________
> gradsusr mailing list
> gradsusr at gradsusr.org
> http://gradsusr.org/mailman/listinfo/gradsusr

--
Jennifer Miletta Adams
Center for Ocean-Land-Atmosphere Studies (COLA)
George Mason University