[postgis-users] Need a "polygon box" of a table instead of the bounding box that returns extent function

[Martin Davis]

I believe that the convex hull of a set of lines is the same as the 
convex hull of the vertices of the lines.  So it should do what you want.

But if you have a reference showing otherwise I'd be interested to see it. 

Oscar Zamudio wrote:
> ha, ha!!,
> My knowledge come from Maths ,and certainly not from Postgis!. The concept
> of Convex Hull (in algorithms and math fields) is always applied to set of
> points and I remember there was a big challenge to find a good method for
> lines (some years ago). But I don't mind Math anymore, if this function
> works to solve my problem, it will be ok for me.
> I will let you know later about my results.
>
> On Mon, May 3, 2010 at 11:29 AM, strk <strk at keybit.net> wrote:
>
>   
>> On Mon, May 03, 2010 at 11:18:03AM -0300, Oscar Zamudio wrote:
>>     
>>> Thanks strk,
>>> As far as I know convex hull basically applies to a collection of
>>>       
>> points...,
>>     
>>> nevertheless, I will try with my set of lines.
>>>       
>> How far does your knowledge come from ? :)
>> http://postgis.refractions.net/docs/ST_ConvexHull.html
>>
>> --strk;
>>
>>  ()   Free GIS & Flash consultant/developer
>>  /\   http://strk.keybit.net/services.html
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>>     
>
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-- 
Martin Davis
Senior Technical Architect
Refractions Research, Inc.
(250) 383-3022