[postgis-users] creating a mask

Fred Lehodey lehodey at gmail.com
Thu Aug 7 06:46:57 PDT 2008

Hi Erik,
you can try something like that:  (?)
select  st_difference(ST_envelope(the_geom),the_geom)  from mytable


On Thu, Aug 7, 2008 at 2:11 PM, erik <whatevar89 at gmail.com> wrote:

> Hello,
> I don't know if the terminology I use is correct but I would like to create
> a mask of layer I have.
> For example, from the shape of the world I would like to keep only the
> oceans, the negative of the initial shape.
> I haven't found any info or documentation about this. Can this be done in
> PostGIS?
> Many thanks!
> Erik
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