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

Mon Oct 19 06:37:12 PDT 2020

Hi Richard,

On 19.10.20 15:17, Richard Duivenvoorde wrote:
> Just checking :-)
> https://www.lfu.bayern.de/gdi/wfs/natur/oefk
>
> which returns:
> Error occurred while processing request
> Type: Status Report
> Message:
> Description: http.400:
> *ArcGIS Server*
>
> So apperently ArcGIS Server, no wonder they have to ask money for everything, they need the money for all the licenses ;-)

Yep, they are completely in the hands of offrippers. The company with
the contract for the software to collect and process ecological data has
this contract till the 80s ... and that's what the software and its
functionality looks alike.

Anyway, this WMS layer was just one example where I could need to
extract the infos so I could match them with the cadastre and other
units for further processing. And maybe I could write those guys a
postcard, asking them to send me the data.
But there are many more examples where my approach would be very helpful
for a lot people around here.

> I thought you wanted to create some PyQGIS script for it.
> The reason this seems not to work (yet), is that QGIS is a c++ program with python bindings for almost everything, but not everything.
> I think devs could make my example work, but there was no use case for it yet...
If there was a python script for something similar, I may be able to
tweak it to my needs, eventually, some day ...
> But... if your are not into Python, what would be your preferred scripting language be then?

I am an (low-to-medium-profile) R guy ;) Doesn't care about indentions
and other crazy stuff ;)

Dived into it during the times when the graphical modeler was breaking
my models with every new version (besides the missing functions)

> Given a WMS getMap request like:
> https://www.lfu.bayern.de/gdi/wms/natur/oefk?SERVICE=WMS&VERSION=1.3.0&REQUEST=GetMap&BBOX=5330491.995354886167,3656773.878684170544,5332123.064803482033,3661911.927476988174&CRS=EPSG:31467&WIDTH=1428&HEIGHT=453&LAYERS=oekoflaechen&STYLES=&FORMAT=image/jpeg&DPI=96&MAP_RESOLUTION=96&FORMAT_OPTIONS=dpi:96
>
> You would end up to create GetFeatureInfo requests like this to return in html:
> 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/html&I=544&J=361&FEATURE_COUNT=10
>
> 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.
>
> So my conclusion, not as easy as you hoped I think, best would be to just get the data from somewhere, not sure if hacking your code will be easier...
> but it
> - would be 'easiest' in PyQGIS (because the 'indentify' is easier to script, because you can use QGIS magic to determine bbox/width and height params)
> - or recreate valid getfeatureinforequests and fire those in some other  script language
>
> Looking that the result in QGIS, there is not so much info in it, just 4 fields.... one of them the area.
Yep, and still enough info for me to work on.
>
> Regards,
>
> Richard Duivenvoorde

Anyway, thanx for your attention and time

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
>>>>>
>>>>> _______________________________________________
>>>>> Qgis-user mailing list
>>>>> Qgis-user at lists.osgeo.org
>>>>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
>>>>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
>>>> --
>>>> Email Signature
>>>> Logo <https://www.geomaster.pt>
>>>> *Geomaster*
>>>> *Jorge Gustavo Rocha* | Software Engineer
>>>> *e:*jgr at geomaster.pt | *m:*+351 910 333 888
>>>> *g:*41.54094,-8.40490 | *v: *510 906 109
>>>> *a: * Rua António Cândido Pinto, 67, 4715-400 Braga
>>>>
>>>>
>>>> _______________________________________________
>>>> Qgis-user mailing list
>>>> Qgis-user at lists.osgeo.org
>>>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
>>>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
>>>>
>>> _______________________________________________
>>> Qgis-user mailing list
>>> Qgis-user at lists.osgeo.org
>>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
>>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user