[postgis-users] generating ocean

[Arnaud Lesauvage]

Christo Du Preez a écrit :
> I would still like to now how to generate oceans from my country 
> boundaries. The problem using different datasets is that the data 
> wouldn't be an exact match, layering it might produce gaps.
> Ill be happy with something like a box with a hole (country boundary) in 
> as a result.

I believe this is what the Difference(geometry A, geometry B) 
function does.
So you could use something like :

SELECT Difference(Expand(county_geometry, 100000), county_geometry))
FROM country_table;

It might use a lot of processing time / memory if the boundaries 
are large though.

--
Arnaud