QGIS - add Layer From URL (GetCapabilities)

Question

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?

• Ian Turton: which alphanumeric part? it is just a map of buildings when I view it
• Lorenzo: So it's not my problem. I can't see anything else because there is nothing else, right?
• csk: 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.
• Lorenzo: 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?
• jbalk: 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

Answer 1

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

• Houska: 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.
• nmtoken: +/- or a WCS, depending on the input data