[geos-devel] supporting filters

[Carl Anderson]

OGC defines the DWithin and Beyond spatial operators recursively in 
section 8.2 of the Filter Encoding 04-095 specification (further 
referenced by the WFS and WMS specs)

http://www.opengeospatial.org/standards/filter

anybody feel like bringing up this confusion with the Open Geospatial 
Consortium folk.

C.


Paul Ramsey wrote:
> Oracle's understanding is the same as mine:
>
> <http://download-west.oracle.com/docs/cd/B19306_01/appdev.102/b14255/sdo_operat.htm#i77653> 
>
> On 28-May-07, at 7:41 PM, Paul Ramsey wrote:
>
>> Is this the Oracle defn also? I had always interpreted DWithin to 
>> mean "within distance of", so that
>>
>> DWIthin(A,B,100) was functionally equivalent to Distance(A,B) < 100
>>
>> P
>>
>> On 27-May-07, at 2:23 PM, Kralidis,Tom [Burlington] wrote:
>>
>>>
>>> Further info from Peter Vretanos (FES 1.0.0 spec editor):
>>>
>>> "According to the BNF in the Cat 1.0 specification DWithin tests to see
>>> whether geometry A is completely within a certain distance of geometry
>>> B.
>>>
>>> I interpret this to mean a "buffer" query.  That is you create a buffer
>>> around A at the specified distance and then do a WITHIN (as defined in
>>> SFSQL) between this new buffer-expanded geometry (A') and the test
>>> geometry B.  If B is completely within A' then the operator 
>>> evaluates to
>>> true
>>>
>>> BEYOND is the opposite of DWITHIN.   If B is completely outside of A'
>>> then the operator evaluates to true."
>>>
>>> Cheers
>>>
>>> ..Tom
>>>
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>>
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