For an example of another block of code that has to deal with
interoperability look at the WMS client code used in the WMS cascade case.
In this case each "external" bounding box handled xplicitly, rewriting to
internal URN syntax, or using forceLatLong as required to accurately
represent the data. With this accurate representation it is reprojected as
quickly possible to the order used by GeoServer to avoid confusion.
--
Jody
Jody Garnett
On Tue, Apr 22, 2014 at 5:50 PM, Andrea Aime
<[email protected]>wrote:
> On Tue, Apr 22, 2014 at 9:12 AM, Sampo Savolainen <
> [email protected]> wrote:
>
>> Hi,
>>
>> There might be a bug in WFS-NG relating to axis order of coordinates
>> returned by layers created by WFS-NG.
>>
>> I created a dummy feature type on one geoserver serving content in
>> EPSG:4258 (northing-easting), then created a feature type in another
>> geoserver by cascading the first server using WFS-NG (WFS 1.1.0). The
>> WFS-NG feature type uses the same CRS.
>>
>> When accessing the first geoserver directly (GetFeature), I get the
>> coordinates in the correct order. But when accessing the cascading feature
>> on the second server (GetFeature again), the coordinates have flipped.
>>
>> While debugging this, I found that the problem is connected to SRS
>> handling in the layer. If "force declared" is chosen, the axis order of the
>> returned features if flipped. Both "keep native" and "reproject native to
>> declared" work fine.
>>
>> In GeoServerFeatureSource.reprojectFilter(), declaredCRS has the wrong
>> axis order (east-north) while nativeCRS has the correct one (north-east).
>> Why is the axis order wrong in declaredCRS? Is this by design / am I
>> missing something, or has WFS-NG initialized the FeatureSource wrong
>> somehow?
>>
>
> Basically for a data source to work properly with GeoServer it has to
> return data in east/north order,
> if you return it in north/east, even if you use the urn forms, it won't
> work.
>
> Longer explanation: in GeoServer the declared EPSG code _has_ to be in the
> EPSG:XYWZ form,
> which in GeoServer means east/north axis order.
> We can't use another authority (http://jira.codehaus.org/browse/GEOS-903),
> we can't use the urn form,
> GeoServer GUI won't understand it and there is code spread around assuming
> the east/north
> axis order that will break if we just loosen the GUI.
>
> The reason why things work in reproject to declared and keep native is
> that much of the underlying code
> can handle axis flipping fine (all the code that uses
> CoordinateReferenceSystem instead of its string
> representation), so as long as we lie about the CRS to the code that deals
> with the string form, we're good.
>
> Options here:
> 1) make GeoServer source data axis order aware (large refactor, many
> little pieces spread around to fix)
> 2) make your data source always return data in east/north order
> 3) have some GeoServer code bits aware of the source data axis order issue
> and wrap it in a reprojecting
> feature source before the rest of the code sees it
>
> Option 1) is expensive, option 2) is not really natural, option 3) can be
> fragile and introduce performance
> overhead if not done properly.
>
> Hmm.. pick your poison?
>
> Cheers
> Andrea
>
> --
> ==
> Meet us at GEO Business 2014! in London! Visit http://goo.gl/fES3aK
> for more information.
> ==
>
> Ing. Andrea Aime
> @geowolf
> Technical Lead
>
> GeoSolutions S.A.S.
> Via Poggio alle Viti 1187
> 55054 Massarosa (LU)
> Italy
> phone: +39 0584 962313
> fax: +39 0584 1660272
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>
> http://www.geo-solutions.it
> http://twitter.com/geosolutions_it
>
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