[QGIS-Developer] GetFeatureInfo: sensitivity on rendered geometry vs original geometry.

[Andreas Neumann]

On 2019-04-12 15:53, René-Luc Dhont wrote:

> Hi Andreas,
> 
> I think QGIS Server has to use the rendered geometries to identify Feature.

yes

> Is it possible to get the  point layer to polygon rendred layer ?

Like Alessandro, I also don't understand this statement. Do you say that
I should convert my point layer to a polygon layer representing the
rendered bounding box? This would be quite difficult for our users. 

Andreas 

> Regards,
> René-Luc
> 
> Le 12/04/2019 à 15:43, Andreas Neumann a écrit : 
> 
>> Hi, 
>> 
>> I'd like to discuss an issue with GetFeatureInfo that we have with point symbols. 
>> 
>> (Point) symbols can have different sizes (sometimes rather large), different anchor points and sometimes even with offset away from the original feature geometry. Often, the rendering of the point symbol differs substantially from the original point geometry. 
>> 
>> Now, our issue is that GetFeatureInfo often fails miserably in such cases. People try to click on the visible symbol, which doesn't correspond to the original geometry. 
>> 
>> One such example WMS: 
>> 
>> https://services.geo.zg.ch/ows/Abfallsammelstellen 
>> 
>> The symbols are rather large, but the anchor point is at the bottom of the symbol. Users now think that they can click anywhere on the symbol, but in fact they can only click on the original geometry at the very bottom of the symbol, taking into account the FI_POINT_TOLERANCE parameter. 
>> 
>> Things get even worse when one wants to identify points that are displayed using the point displacement renderer. There, GetFeatureInfo is only sensitive on the center point, and not at all at the rendered points at a completely different position. 
>> 
>> Now my question: could we improve QGIS server that GetFeatureInfo responds to the bounding boxes of the rendered geometries (as opposed to the raw geometries), taking into account sizes, offsets, etc. 
>> 
>> Would this be technically possible?  
>> 
>> Would others also think that this is useful to have? 
>> 
>> Or would this even contradict OGC standards? 
>> 
>> Do other WMS servers implement such behaviors (Geoserver, UMN)? 
>> 
>> Thanks for the discussion, 
>> 
>> Andreas 
>> 
>> _______________________________________________
>> QGIS-Developer mailing list
>> QGIS-Developer at lists.osgeo.org
>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer
>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-developer
> 
> _______________________________________________
> QGIS-Developer mailing list
> QGIS-Developer at lists.osgeo.org
> List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer
> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-developer
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/qgis-developer/attachments/20190412/e83a09d2/attachment.html>