[postgis-users] two different geometries with the same Astext

[Paul Ramsey]

I would suggest looking up the precise definition of Within() in the  
SFSQL. I am not sure that equality implies within. I think a.within 
(b) implies that a is in the interior of b, but not the boundary.  
Could be wrong, of course. What is the relate() pattern between the  
two objects? That is a more interesting result.

P

On 18-Jul-05, at 9:03 AM, Stephen Woodbridge wrote:

> Miguel de la Fuente wrote:
>
>> Hello, I'looking for help with something that already happens to  
>> me in
>> the past, comparing two geometries with equals() return false but  
>> when
>> I get the AsText() of both it was the same.
>> Right now I'm having a similar problem with within(), when I ask if a
>> geometry1 is within a geometry2 in another table, both
>> multilinestrings,  the result is false.
>> I ask the AsText of both and see that the geometry1 is one segment of
>> geometry2, so it is within it.
>> And, if I ask wthin(GeometryFormText(AsText 
>> (geometry1)),GeometryFormText(AsText(geometry2)))
>> return true
>> Then, why wthin(geometry1,geometry2) return false ?
>> Can anyone help me??
>>
>
> This sounds like floating point comparisons failing because of  
> numerical rounding issues.
>
> strk, Is there an epsilon value that is used to comparing floating  
> point values? Is this accessible or settable at runtime?
>
> -Steve W.
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