[postgis-users] how to create a hole in a polygon table?

[Robert Buckley]

Thanks for the advice.

Unfortunately I don´t understand what you have just told me....half-brush? half-circle?

are these sld specifications?...I am delivering wms data using sld´s to style the data.

could you please clarify?

cheers,

Rob


________________________________
 Von: Paul Ramsey <pramsey at opengeo.org>
An: Robert Buckley <robertdbuckley at yahoo.com>; PostGIS Users Discussion <postgis-users at postgis.refractions.net> 
Gesendet: 19:20 Dienstag, 28.Februar 2012
Betreff: Re: [postgis-users] how to create a hole in a polygon table?
 
Rather than geometry processing, work on your rendering engine. You
can usually achieve an interior band (the classic National Geographic
political boundary, yes?) with a half-brush (rather than a full
circle, use a half-circle), and just ensuring your polygons are
consistently oriented.

P.

On Tue, Feb 28, 2012 at 10:04 AM, Robert Buckley
<robertdbuckley at yahoo.com> wrote:
> Hi,
>
> I am trying to create an inner buffer of a polygon geometry table.
> Unfortunately this is the only way I can think of which will enable me to
> make a certain symbol for a polyon layer. The SLD Filter "difference" might
> do it, but it needs to be nested and i´m not sure if this is possible.
>
> anyway....My polygons need to be symbolized with a thin outline AND an
> inside Buffer of 3 mm(150m  at a scale of 1:50 000)....in essence just an
> inside ring.
>
> This means I need to first buffer my polygon geometry and then substract the
> buffer from the original polygon. = ST_Difference (i think!?!)
>
> my attempt created some geometries but not what I was expecting...
>
> create view rrop08.rrop_01_13_innerbuffer AS
>
> SELECT ST_Difference(a.st_buffer, b.the_geom)
>
> FROM rrop08.rrop_01_13_buffer a, rrop08.rrop_01_f b;
>
>
> rrop08.rrop_01_f  = the original polyon
>
> rrop08.rrop_01_13_buffer = the inner buffer
>
>
>
>
>
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