[postgis-users] I used ST_Buffer in hope of creating a polygon around my original polygon (rectangle), but I ended up with a circle with the center point right at the center of the polygon

googling1000 googling1000 at yahoo.com
Sun Jul 6 23:06:51 PDT 2008

Thanks for your help.
Now I get it.
you're the best.

Kevin Neufeld wrote:
> googling1000 wrote:
>> Hi,
>> I'd appreciate it if someone can help me figure this out.
>> I thought ST_Buffer will take in any geometry and make a "buffer" around
>> that geometry.
> Yes, it does.
>> So, if you give it a rectangular polygon, you will get a bigger
>> rectangular
>> polygon.
> Nope.  You'll get a bigger rectangular polygon ... with rounded corners. 
>> But, I keep getting a circle, and it looks like postgis found the center
>> of
>> the polygon and made that point the center of the resulting circle.
> If you've made your buffer large enough, it would indeed look like a 
> circle since all you'll see is the four rounded corners.
> If you're after a larger rectangle, try simply expanding the bounding 
> box using ST_Expand().  Alternatively, you could try ST_Scale().
> Cheers,
> -- Kevin
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