[Qgis-user] Programmatically extract WMS data based on point layer?

Mon Oct 19 07:51:06 PDT 2020

Hi Richard,

I now dared to have a closer look at your findings.

On 19.10.20 15:17, Richard Duivenvoorde wrote:Or in plain/text (VERY
ugly formatted!):
> https://www.lfu.bayern.de/gdi/wms/natur/oefk?SERVICE=WMS&VERSION=1.3.0&REQUEST=GetFeatureInfo&BBOX=5330491.99535488616675138,3656773.87868417054414749,5332123.06480348203331232,3661911.92747698817402124&CRS=EPSG:31467&WIDTH=1427&HEIGHT=453&LAYERS=oekoflaechen&STYLES=&FORMAT=image/jpeg&QUERY_LAYERS=oekoflaechen&INFO_FORMAT=text/plain&I=544&J=361&FEATURE_COUNT=10
>
> So theoretically you could create some script to just fire the GetFeatureInfo-requests. Main drawback is for a request to be valid, your bbox and width/height should be in par with your x,y (mmm, ArcGis apparently uses I J, which are pixels! in the bbox/width/height)... So I think that is pretty difficult.
>
>
errm, does the I and J represent the pixel at the coordinate relative to
the bbox? And how did you figure out the values?

Cheers,

Bernd

> On 10/19/20 2:45 PM, Bernd Vogelgesang wrote:
>> Hi Richard,
>>
>> your last question first: Nope, there is definitely no WFS (would be too easy). I am living in Bavaria, the home of "Laptop and Lederhosen". Our administrations are among the greediest and most retarded (offering hardly any WFS which then mostly have to paid as well) in Germany.
>>
>> How would I know this is a Geoserver instance? The url of the WMS is |https://www.lfu.bayern.de/gdi/wms/natur/oefk?|
>>
>> My "python" is actually nonexistant, so I was hoping that there was something "prebuilt" in someone's drawer already. But as my web research showed, there does seem to be much on this topic besides of "not possible".
>>
>> It's a bit mystical to me why QGIS can show the result of a click on a layer, but not store the data by any means ...
>>
>> Mhm ...
>>
>> Bernd
>>
>> On 19.10.20 14:07, Richard Duivenvoorde wrote:
>>> Hi Jorge, Bernd,
>>>
>>> I thought to play with that, but ...
>>>
>>> although I get a valid result, I cannot get to the actual features in python:
>>>
>>> TypeError: unable to convert a C++ 'QgsFeatureStoreList' instance to a Python object
>>>
>>> So I'm not sure if you could (currently) easily come to the actual feature...
>>>
>>>
>>> What I did (working with a national buildings WMS, and a (to me) known valid x,y,width/height etc:
>>>
>>> l=qgis.utils.iface.addRasterLayer(
>>> "crs=EPSG:28992&layers=Bebouwingvlak&styles=&format=image/png&url=https://geodata.nationaalgeoregister.nl/kadastralekaart/wms/v4_0?", # uri
>>> "buildings", # name for layer (as seen in QGIS)
>>> "wms" # dataprovider key
>>> )
>>>
>>> result = l.dataProvider().identify( QgsPointXY(104606,490213),
>>>               QgsRaster.IdentifyFormatFeature,
>>>               QgsRectangle(104391.1406077263819,490161.0749502293766,104899.6563292678911,490283.3410253541078),
>>>               1465,
>>>               352,
>>>               96)
>>> print(result.isValid()) # prints True
>>> print(result.results())
>>> # prints TypeError: unable to convert a C++ 'QgsFeatureStoreList' instance to a Python object
>>>
>>> Regards,
>>>
>>> Richard Duivenvoorde
>>>
>>> PS @Bernd: you are sure there is no WFS running there (if it is a Geoserver instance, it often has (silently) also a WFS....)?
>>>
>>> On 10/19/20 1:36 PM, Jorge Gustavo Rocha wrote:
>>>> Hi Bernd,
>>>>
>>>> Try rlayer.dataProvider().identify()
>>>>
>>>> Checks the docs at https://docs.qgis.org/3.10/en/docs/pyqgis_developer_cookbook/raster.html#query-values
>>>>
>>>> Good luck,
>>>>
>>>> Jorge
>>>>
>>>> Às 12:25 de 19/10/20, Bernd Vogelgesang escreveu:
>>>>> Hi there,
>>>>>
>>>>> unfortunately I am provided with data only in form of a WMS layer
>>>>> representing areas as polygons.
>>>>> These areas match with the cadastral boundaries.
>>>>> I am looking for a way how to hand over the data from the WMS to my
>>>>> cadastral units to be able to really work with these informations.
>>>>>
>>>>> I created a "Point on surface" layer of the cadastre.
>>>>> Is there any pythonic or other way to "mimic" the "Identify features"
>>>>> click on that layer with the coordinates of those points and store the
>>>>> results?
>>>>>
>>>>> I assume, that each click is a server request, so running these (in my
>>>>> case) 8000 "cĺicks" should not be sent in a millisecond, but with some
>>>>> pause.
>>>>> It doesn't really matter how long this takes, cause it only has to be
>>>>> done once and would be in any case faster than manually clicking and
>>>>> noting the data.
>>>>>
>>>>> Obviously, this is not what the provider of the data intends, but it's
>>>>> like an act of self-defence against a stubborn and bureaucratic
>>>>> administration.
>>>>> So, data rebels, come to help please ;)
>>>>>
>>>>> Cheers,
>>>>>
>>>>> Bernd
>>>>>
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