Restarting this thread, although perhaps you saw the update in the meeting
notes.
The XYZM support has been merged to jts master branch, so you should be in
position to start your work (using 1.16.0-SNAPSHOT). Expect to issue a
1.16.0-RC when you are ready to merge your work.
James is starting the release cycle for JTS on gitter, takes about three
weeks, putting us in position to make an official 1.16.0 release in
September.
--
Jody Garnett
On Tue, 31 Jul 2018 at 05:09, Nuno Oliveira <[email protected]>
wrote:
> Hi all,
>
> I'm working on bringing support for M measurements in WFS. Some parallel
> work
> related with this is happening on JTS:
>
> * https://github.com/locationtech/jts/pull/293
> * https://github.com/locationtech/jts/pull/291
>
> If I understood the JTS situation correctly, currently is already possible
> to
> store the M measurements values in
> JTS geometries (XYZM or XYM), but is up to the client code to identify
> them and
> handle them. The main goal of the
> changes above is to create a cleaner \ explicit JTS API, i.e. make it
> easier for
> client code to understand what
> type of coordinates are available and make it easier to access the
> relevant
> ordinates.
>
> I'm not aware of JTS release schedule, but I guess these changes will land
> on
> the next major release ? Which means
> that they will not be available for us to use in GT\GS anytime soon. I
> would
> like to have the M support for WFS to
> land on master before the next GeoServe 2.14.x release, i.e. it need to
> land on
> master next week at most.
>
> Not using the new JTS API means that we will need to store the number of
> measures in the geometry user data.
> This would be aligned with the new JTS API approach, quoting Jody comment
> on one
> of the pull request above:
>
> I ended up having CoordianteSequence.getDimension() as described in the
> conversation above, and
> CoordianteSequence.getMeasures() being the number of measures (so if we
> have
> XYZM dimension is 4 and measures is 1.
>
> ... so when the new JTS API becomes available we just need to switch to
> get the
> measures value from the JTS API
> instead of the user data.
>
> That said, supporting M measurements in WFS will require:
>
> 1. correctly read geometries with measurements from data sources
> 2. correctly encode the measurements in the output formats
> 3. correctly handling measurements when doing certain operations, e.g.
> re-projections
>
> The following issue in GeoServer as an interesting discussion about this:
>
> https://osgeo-org.atlassian.net/browse/GEOS-8858
>
> Using PostGIS and GML 3.2. as an example:
>
> 1. we will need to take into account the possibility of a measurement
> value
> when decoding geometries from postgis:
>
> https://github.com/geotools/geotools/blob/master/modules/plugin/jdbc/jdbc-postgis/src/main/java/org/geotools/data/postgis/WKBReader.java#L194-L197
>
> 2. the correct geometry type (LINESTRINGM, LINESTRINGZM, etc ...) can
> be
> obtained from the database metadata
>
> 3. vouch for the M measurement when encoding coordinates, e.g.
> linestring
> encoding for GML 3.2
>
> https://github.com/geotools/geotools/blob/master/modules/extension/xsd/xsd-gml2/src/main/java/org/geotools/gml2/simple/GMLWriter.java#L287-L301
>
> In point 1 or 2 we will store in the user data the measurements number and
> use
> it in point 3.
>
> Comments on this are welcome :)
>
> Cheers,
>
> Nuno Oliveira
>
> --
> Regards,
> Nuno Oliveira
> ==
> GeoServer Professional Services from the experts!
> Visit http://goo.gl/it488V for more information.
> ==
>
> Nuno Miguel Carvalho Oliveira
> @nmcoliveira
> Software Engineer
>
> GeoSolutions S.A.S.
> Via di Montramito 3/A
> 55054 Massarosa (LU)
> Italy
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>
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