Hello !!
I would like to make a spatial request editor in my GIS and I know that GeoServer handles the spatial operators I need (those mentionned in the filter encoding imp. spec. of the OGC). But what I don't know is how GeoServer handles these operators.
I looked at PostGis documentation, and I saw that spatial operators (&&, @ ...) work with the bounding boxes of the geometries. That doesn't seem to be very accurate...
Does geoserver work on these operators ???
I also searched a little around this topic and I found the powerfull JTS API. Then, I found that some courageous people were porting JTS to C++ in order to have the complete Simple Features Specification of the OGC implemented in postgis. But GEOS hasn't been released yet (the beta will come soon, take a look at the mailing list on http://geos.refractions.net)
Maybe it could be a good improvement for geoserver to handle spatial operators using the GEOS implementation in postgis !
For the moment, I need to find a way to make my "request editor". So I choosed to use the current GeoServer capabilities and maybe get innaccurate results. Then I will see :
If you (geoserver devels) plan to use GEOS spatial operators in GeoServer, it will be ok.
If you don't plan it, maybe I will use geoserver results to get interesting geometries for each request and then relaunch the request with JTS using the geometries exported in WKB or WKT. (Will surely be slow :-[ )
Hope you understood my bad english.
Any suggestions are welcome.
Steph
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Geoserver currently handles BBOX using the postgis && function, and the
rest of the operators are handled using the JTS api. GeoServer uses JTS
internally, all postgis geometries are turned into jts geometries,
allowing us to easily support all the spatial operators that the api does.
As for GEOS, we are definitely excited by its release, as it will greatly
speed up all the spatial operators. For now we have to create jts
geometries for all the possible features, and then filter out the ones
that don't match. With the spatial operators supported in the db we will
be able to avoid a lot of overhead. Once GEOS comes out it should be
quite easy to implement, org.geotools.filter.SQLEncoderPostgis just needs
to add a few functions to turn the filters into the appropriate sql call.
The only tricky part will be figuring out if the instance of postgis does
have geos installed, so that we don't try to use the filters on postgis
installs that won't understand it. But yes, you should be able to get
accurate results with geoserver right now, as we just rely on jts, and in
the future geos will be supported, for accuracy and greater speed.
Chris
On Wed, 2 Jul 2003, W. Steph wrote:
Hello !!
I would like to make a spatial request editor in my GIS and I know that
GeoServer handles the spatial operators I need (those mentionned in the
filter encoding imp. spec. of the OGC). But what I don't know is how
GeoServer handles these operators.
I looked at PostGis documentation, and I saw that spatial operators (&&, @
...) work with the bounding boxes of the geometries. That doesn't seem to be
very accurate...
Does geoserver work on these operators ???
I also searched a little around this topic and I found the powerfull JTS
API. Then, I found that some courageous people were porting JTS to C++ in
order to have the complete Simple Features Specification of the OGC
implemented in postgis. But GEOS hasn't been released yet (the beta will
come soon, take a look at the mailing list on http://geos.refractions.net)
Maybe it could be a good improvement for geoserver to handle spatial
operators using the GEOS implementation in postgis !
For the moment, I need to find a way to make my "request editor". So I
choosed to use the current GeoServer capabilities and maybe get innaccurate
results. Then I will see :
If you (geoserver devels) plan to use GEOS spatial operators in GeoServer,
it will be ok.
If you don't plan it, maybe I will use geoserver results to get interesting
geometries for each request and then relaunch the request with JTS using the
geometries exported in WKB or WKT. (Will surely be slow :-[ )
Hope you understood my bad english.
Any suggestions are welcome.
Steph
_________________________________________________________________
MSN Messenger 6 http://g.msn.fr/FR1001/866 : ajoutez une image à votre
pseudo pour dialoguer avec vos amis
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