Hi list,
how difficult would it be to create a WPS process that does linear
referencing (e.g. when the underlying datastore is PostGIS, or Oracle
Spatial)?
Is WPS suited for such an approach at all, or would WFS 2.0 be more suitable?
Best regards,
Bart
On Tue, Jan 25, 2011 at 3:40 PM, Bart van den Eijnden (OSGIS)
<bartvde@anonymised.com> wrote:
Hi list,
how difficult would it be to create a WPS process that does linear
referencing (e.g. when the underlying datastore is PostGIS, or Oracle
Spatial)?
A WPS process never knows what the data source is, it gets feature collections
that might be coming from whatever, a shapefile, oracle, a remote sent
shapefile,
a GML collection.
If a process wants to leverage postgis you should take that
collection, import it into a postgis
you have configured as the processing one, execute the sql to do
whatever analysis you
need, get the results back as another feature collection, return it.
And manage the lifecycle of the temp tables you created so that we don't end up
with many little stale tables. There are some classes in WPS that can
help to manage
these temp resources.
If the process just need to compute the position at 10 miles along a
road starting
from a certain point it's probably easier to code it in pure java
Is WPS suited for such an approach at all, or would WFS 2.0 be more suitable?
WPS seems better suited as you have to return new data that does not necessarily
abide to the WFS schema returned by DescribeFeatureType for that feature type.
Cheers
Andrea
--
Ing. Andrea Aime
Technical Lead
GeoSolutions S.A.S.
Via Poggio alle Viti 1187
55054 Massarosa (LU)
Italy
phone: +39 0584962313
fax: +39 0584962313
http://www.geo-solutions.it
http://geo-solutions.blogspot.com/
http://www.linkedin.com/in/andreaaime
http://twitter.com/geowolf
-----------------------------------------------------
On Wed, Jan 26, 2011 at 12:49 PM, Andrea Aime
<andrea.aime@anonymised.com> wrote:
On Tue, Jan 25, 2011 at 3:40 PM, Bart van den Eijnden (OSGIS)
<bartvde@anonymised.com> wrote:Hi list,
how difficult would it be to create a WPS process that does linear
referencing (e.g. when the underlying datastore is PostGIS, or Oracle
Spatial)?A WPS process never knows what the data source is, it gets feature collections
that might be coming from whatever, a shapefile, oracle, a remote sent
shapefile,
a GML collection.
Btw, clarification here. A standard, well designed, chainable, discoverable,
secure WPS process just gets feature collections.
Otherwise a WPS process is free to do whatever it pleases and just get,
say, the name of a layer or the name of a table (or even the connection params
to the db) in the database and work off those.
However you lose the ability to compose the process with others, you bypass
the security subsystem solid, you have to perform all your validation inside
the process (whilst calling the internal wfs you have that built in), you
have to specify all your filtering explicitly as a further parameter (whilst
with built in wfs querying is built in again, and the same goes for
attribute slicing
and reprojection), the client cannot know anymore the set of valid values
for your parameter (what tables are in the database, what is their structure?
you get that from information from WFS), the client cannot anymore provide its
own data, and so on.
I'm not saying one should never do a process that bypasses the normal
featurecollection/grid coverage in/out structure, but the moment you do
you're giving up a lot, you make a specialty process that only custom built
clients can use instead of having a reusable processing block.
So judge on a case by case basis, and see what the actual needs are.
Cheers
Andrea
--
Ing. Andrea Aime
Technical Lead
GeoSolutions S.A.S.
Via Poggio alle Viti 1187
55054 Massarosa (LU)
Italy
phone: +39 0584962313
fax: +39 0584962313
http://www.geo-solutions.it
http://geo-solutions.blogspot.com/
http://www.linkedin.com/in/andreaaime
http://twitter.com/geowolf
-----------------------------------------------------
The other approach is to use a function to handle the linear part of LRS.
Use either app schema with a mapping expression; or a view in your database; to combine the original geometry and the LRS range into a geometry for publication via WFS.
Actually with the recent rendering trick of using a function expression as part of an SLD file you can make it a WMS only solution if you like.
Cheers,
Jody
On 26/01/2011, at 12:40 AM, Bart van den Eijnden (OSGIS) wrote:
Hi list,
how difficult would it be to create a WPS process that does linear
referencing (e.g. when the underlying datastore is PostGIS, or Oracle
Spatial)?Is WPS suited for such an approach at all, or would WFS 2.0 be more suitable?
Best regards,
Bart------------------------------------------------------------------------------
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