We had similar challenge when drawing WMS, if I remember we reproject to wgs84 3D, drop the Elevation, and then reproject from wgs84 to the final 2d projection.
That is our own assumption to draw 3D data, folks can use function calls as part of their WFS query to get a similar result can they not? It may be sensible to ask users to apply a function for such an usual case…. Jody On Mon, Oct 11, 2021 at 6:21 AM Niels Charlier via GeoTools-Devel < geotools-devel@lists.sourceforge.net> wrote: > Hello Jukka, > > Thanks for your answer. I guess I wanted to ask the opinion of the > community on how to proceed. I see at this point two options: > > 1) stick with the suggestion of the standard, and do not project 3D->2D. > (The easiest solution, what I already have). > > 2) allow reprojection 3D->2D and only prevent 2D->3D reprojection > (Andrea's suggestion). This will require quite a lot of further core > changes: > - modification of Query in geotools to allow reprojection per geometry > (with backwards compatibility for the current existing fields). > - modification of GetFeature implementation in geoserver so that without > srsName specified, the 'right' geometries are being reprojected to the > right CRS. > > Kind Regards > > Niels > > On 09/10/2021 15:00, Rahkonen Jukka (MML) wrote: > > Hi, > > > > If I understand right your message and the standard, WFS 2.0 does not > have any support for reprojecting both 2D and 3D geometries with a single > request because srsName can appear only once in GetFeature. So if srsName > is some 2D crs then 3D geometry is not projected and if srsName is some 3D > crs then the 2D geometry is not projected. That feels suboptimal. > > > > I agree that transforming 3D CRS into 2D when there is no srsName in > GetFeature request is clearly unwanted behaviour. Otherwise I think that > WFS 2.0 does not feel ready for handling reprojection of multiple > geometries in different native CRS. The solution could to make it possible > in WFS to give a separate srsName for each geometry. It seems that the > problem will be the same with OGC API Features. The core says that features > may have several geometries but the crs extension supports only one crs in > the items request. > > > > It may be impossible to do this with so that it is both right according > to the standards and reasonable for the users but I wish you a good luck. > > > > -Jukka Rahkonen- > > > > > > -----Alkuperäinen viesti----- > > Lähettäjä: Niels Charlier via Geoserver-devel < > geoserver-de...@lists.sourceforge.net> > > Lähetetty: lauantai 9. lokakuuta 2021 15.05 > > Vastaanottaja: Geotools-Devel list <geotools-devel@lists.sourceforge.net>; > Geoserver-devel <geoserver-de...@lists.sourceforge.net> > > Aihe: [Geoserver-devel] reprojections and multiple geometries > > D- > > Hello Everyone, > > > > I am sending this email to both geotools and geoserver lists because the > matter concerns both. > > > > I recently made a PR to improve geotools/geoserver behaviour with > respect to multiple geometries that have different CRS. > > (https://github.com/geotools/geotools/pull/3642) One of the matters > that is being discussed between Andrea and me is the expected behaviour on > reprojection. > > > > I attempted to follow the instructions and examples given for the > "srsName" parameter specified by the OCR WFS2.0 specs > > (https://docs.opengeospatial.org/is/09-025r2/09-025r2.html#95 > > <https://docs.opengeospatial.org/is/09-025r2/09-025r2.html#95>) These > seem to suggest that geometries that have a 'incompatible' CRS are simply > not reprojected, without failure. The only example given for > 'incompatibility' is having a different dimension. Andrea noted that > transformation only fails in the direction 2D->3D while it works the other > way around, so that it should still be reprojected in that case. > > However, the example given in the specs suggests explicitely that a 3D > geometry would not be converted to a 2D srsName. This seems to be what is > expected in my use case as well. > > > > The problem is complicated further by the fact that in geoserver, the > implementation of GetFeature sometimes explicitly specifies a reprojection > CRS in the query, even if there was no srsName in the http request (the > reason has something to do with how different wfs versions handle crs > encoding and axis order. ) What would happen then is that even when no > srsName is specified, the 3D CRS is always being transformed to 2D, which > is clearly unwanted behaviour. > > > > Inspire schemas often require feature types with a (primary) 2D geometry > and a (secondary) 3D geometry. > > > > Kind Regards > > > > Niels > > > > > > > > _______________________________________________ > > Geoserver-devel mailing list > > geoserver-de...@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/geoserver-devel > > > _______________________________________________ > GeoTools-Devel mailing list > GeoTools-Devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/geotools-devel > -- -- Jody Garnett
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