Hi,

WMTS typically supports a rather small number of tilematrices and tiles are 
usually cached, so it makes a lot of sense to advertise the available matrices 
and utilize them. On the other hand WMS maps are created on-the-fly and there 
is very low technical cost on the server side to support however many 
projections. WMS standard also does not define any default CRS and the first 
one on the list in GetCapabilities does not need to be the best.

I guess that Geoserver is the most common WMS server in the world and amazingly 
many Geoservers run with the default settings. It means that there are tens of 
thousands WMS services which support 6782 different projections for each layer 
(checked from Geoserver version 2.25.3). I would not like them all to be 
reported as subdatasets.

I can see that ogrinfo and the OGC API Features driver report the list of 
supported projections. Test with ogrinfo 
OAPIF:https://ogc-api.nrw.de/inspire-us-feuerwehr -al -so shows "Supported SRS: 
OGC:CRS84, EPSG:25832, EPSG:25833, EPSG:4258, EPSG:4326, EPSG:3395, EPSG:3857, 
EPSG:3034, EPSG:3035"
Something similar might be an option for gdalinfo, but still about 6782 EPSG 
codes per layer is too much to be viewed by default. Maybe the CRS list could 
be reported under some metadata domain that user could read on demand?

-Jukka Rahkonen-









Lähettäjä: gdal-dev <gdal-dev-boun...@lists.osgeo.org> Puolesta Michal 
Kowalczuk via gdal-dev
Lähetetty: tiistai 10. syyskuuta 2024 15.15
Vastaanottaja: gdal-dev@lists.osgeo.org
Aihe: Re: [gdal-dev] WMS supported SRS

I found that there was a similar issue in 2021 without any specific answer:
https://www.mail-archive.com/gdal-dev@lists.osgeo.org/msg35549.html

I wonder if getting SUBDATASETS shouldn't return the result in a similar way as 
it does for WMTS service,
where GDAL generates paths to all layer/tilematrix/tilematrixset combination.
For example if layer is available in 3 SRS, GDAL produces 3 subdatasets, so 
using only SUBDATASE_NAME property user has access to all map services shared 
by WMTS server.
In my opinion, GDAL should use the same approach for WMS.

Does anyone object?
I will then submit a new feature request/bug report.

Best regards and have a nice day
Michał Kowalczuk

pon., 9 wrz 2024 o 16:17 Michał Kowalczuk 
<michkowalc...@gmail.com<mailto:michkowalc...@gmail.com>> napisał(a):
Hi,
Does GDAL provides a method to get supported spatial reference systems by WMS 
service?
GDALGetMetadata(SUBDATASETS) generate links only for the first (default) SRS 
from GetCapabilities, so this won't be helpful.
Working with WFS I can get supported SRS using OGR OGR_L_GetSupportedSRSList 
function.
Does GDAL offers something similar for WMS, or should I get this information 
from GetCapabilities XML by myself?

Regards,
Michal
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