[mapserver-users] WFS Intersect with gml:box

[Rahkonen Jukka]

Hi,

"Intersect" means the same as "not disjoint", that the two geometries have at least one point in common. Thus WFS Intersects should select the point that is inside the "box" in the query. I made a quick test with OpenJUMP which is using JTS and it really does select such a point with a apatial query Intersects.

When it comes to Intersects and BBOX, I am remembering that the specs say that they are synonyms. I know that Geoserver has differentiated them in such a way that Intersects is doing a real comparison of geometries which gives topologically correct result but which may be slow.  BBOX is doing the comparison by using the bounding boxes of the geometries which can be much faster but it may select features which are actually disjoint. Two parallel lines is one example. Therefore BBOX with Geoserver always gives at least as many features as Intersects.

I made a quick search and this seems to be good reading:
http://gis.hsr.ch/wiki/images/3/3d/9dem_springer.pdf

-Jukka Rahkonen-

-----Alkuperäinen viesti-----
Lähettäjä: mapserver-users-bounces at lists.osgeo.org puolesta: Yewondwossen Assefa
Lähetetty: ke 30.3.2011 22:34
Vastaanottaja: mapserver-users at lists.osgeo.org
Aihe: Re: [mapserver-users] WFS Intersect with gml:box
 
On 30/03/2011 2:30 PM, Joaquín Rodriguez-Guerra Urcelay wrote:
> Hello,
>
> I was finally able to build the source code, and I am not getting the error anymore :D (with Latest Release Branch, with trunk wfs was not working for me)
>
> But I am not getting the result I was expecting. Maybe I am wrong, but I thought that bbox operation would return all geometries contained in the box, and intersect would return all geometries contained in the box and also those who are not contained completely, but a part of them. Is this right??
I think intersects in this case really returns  only those features that 
intersect and not all that are completely contained.

Assefa
-- 

----------------------------------------------------------------
Assefa Yewondwossen
Software Analyst

Email: yassefa at dmsolutions.ca
http://www.dmsolutions.ca/

Phone: (613) 565-5056 (ext 14)
Fax:   (613) 565-0925
----------------------------------------------------------------


_______________________________________________
mapserver-users mailing list
mapserver-users at lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/mapserver-users