[postgis-users] st_buffer (radius_of_buffer)

[Martin Davis]

No, actually buffer with a 0 radius means "the valid polygon which 
contains only the points in the input geometry".

Since you can't create a valid polygon using a 0 radius to buffer a 
non-polygon (line or point), buffer returns an empty geometry.  In other 
words, buffer(geom, 0) is only meaningful when geom is polygonal.

This should probably be clarified in the documentation.

ibrahim saricicek wrote:
> hi all;
>
> I think 0.0 of radius means the object itself? Am i wrong?
>
> I'm inserting a row to my route table
>
> insert into route (the_geom) select 
> st_transform(ST_GeomFromText('SRID=4326;multilinestring((30 20,31 
> 21,32 22))'),900913)
>
> why the result of this is false? that is a point on my route. what is 
> defined with '0.0 of radius'?
> the result is true for 0.1 to 0.000000001? Why for 0.0000000001 
> radius, result is false?
>
> select
> st_intersects(st_buffer(route.the_geom,0.0), st_geomFromText('POINT(30 
> 20)',4326)) 
> as result
> from route
> ------------------------------------------------------------------------
>
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-- 
Martin Davis
Senior Technical Architect
Refractions Research, Inc.
(250) 383-3022