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I'm trying to add a layer to my QGIS project from this URL: http://quegis.labcd.unipi.it/cgi-bin/qgis_mapserv.fcgi?SERVICE=WMS&VERSION=1.3.0&REQUEST=GetCapabilities

Using a WMS connection, I'm able to open it in jpeg or PNG format, but I don't know how to retrieve the alphanumeric part, i.e. feature attributes, which is the interesting part for me. Am I making a mistake or is it impossible via WMS?

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    which alphanumeric part? it is just a map of buildings when I view it – Ian Turton♦ Dec 5 '19 at 17:16
  • So it's not my problem. I can't see anything else because there is nothing else, right? – Lorenzo Dec 5 '19 at 17:38
  • What makes you think there should be an alphanumeric part? Are you expecting an attribute table? A WFS (web feature service) layer could have an attribute table, but a WMS (web map service) layer doesn't have attributes because it's just a raster image. – csk Dec 5 '19 at 17:48
  • I need an attribute table, but I'm not sure that there is one. Is there a way to verify if the alphanumeric part exists? – Lorenzo Dec 5 '19 at 17:53
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    WMS only provides image tiles. There is no 'alphanumeric part' or attribute table. It does not exist when working with a WMS. You need a WFS – jbalk Dec 5 '19 at 18:05
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You can get attribute information from a WMS by using a GetFeatureInfo request. A GetFeatureInfo request is a request for information at a point location (a pixel location in the map image).

GetFeatureInfo is an optional operation of a WMS, you can tell whether a layer supports such a query by looking at the GetCapabilities response, in your example it is (queryable="1"):

<Layer queryable="1">
    <Name>benigeo</Name>
    <Title>benigeo</Title>

In QGIS the GetFeatureInfo request is performed using the 'Identify Features` tool.

In this case there is also an associated WFS:

http://quegis.labcd.unipi.it/cgi-bin/qgis_mapserv.fcgi?SERVICE=WFS&REQUEST=GetCapabilities

And you could fetch data using a GetFeature request

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  • By the way, it's actually pretty frequent that a published WMS service is shadowed by a WFS which may or may not be publicized. Ditto ArcGisMapServer -> ArcGisFeatureServer. It's always worth just making the obvious URL changes and seeing if it can be coaxed into working. Not always, of course. – Houska Jan 28 '20 at 18:43
  • +/- or a WCS, depending on the input data – nmtoken Jan 28 '20 at 18:48

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