I am trying to extract geological information from the OneGeology portal unfortunately most of the data there only consists of WMS data.

For example, is it feasible to extract a particular legend class from http://services.azgs.az.gov/arcgis/services/OneGeology/AZGS_USGIN_Geology/MapServer/WMSServer

into a vector form? Or is the best that I can do is to use GDAL to translate the image into a geospatially referenced image?

Note -- OneGeologyPortal does allow for one to save the WMS into KML/WMC but I am unable to open either in a GIS program(ArcGIS/QGIS). Google Earth opens the file but the image resolution is severely deteriorated.

  • The KML created by the OneGeology Portal, is just a wrapper for the WMS service; that is, to allow the WMS service to be used in Google Earth. The resolution should be no different as the services are the same.
    – nmtoken
    Jan 26, 2017 at 11:54
  • WMC is used to share the WMS workspaces, so you can share your maps with a colleague, or come back to your view at a later stage, it is not a format for extracting data. WMC can be used in OpenLayers 2 and through an ArcGIS plugin, or the portal.
    – nmtoken
    Jan 17, 2020 at 9:03
  • It's not well documented, but many of the OneGeology services also expose a simple feature WFS.
    – nmtoken
    Jan 17, 2020 at 9:04

2 Answers 2


As long as you access this data through the WMS protocol, I'm afraid you'll receive only raster (image data).

If this provider gives access to this data through vector formats/protocol (WFS, GML, Geojson, KML...), this would be the way to go.

About the "not working" KML file, have you simply tried to open it with Google Earth ?

  • When I save using the onegeology portal into kmz, it tries to add the extension .kmz[1] which is not recognized by google earth. Manually changing that to .kmz produces an image readable by google earth however importing that to QGis gives me the error 'test.kml is not a valid or recognized data source'. ArcGIS gives me using kml to layer - 'Error 000401: No features were found for processing'
    – GeoPy
    Sep 7, 2012 at 13:37
  • The extension issue is not really problematic, it is more than probably simply set by your browser. Renaming it is perfect. For Qgis, you should try to rename your test.kmz to test.zip, unzip it and then load the resulting KML file into QGIS.
    – niconoe
    Sep 7, 2012 at 13:41
  • 1
    Unfortunatley, windows is unable to unzip as it does not contain anything. Looking at the source code of the kmz file I assume that it actually might just reference the original wms server location...
    – GeoPy
    Sep 7, 2012 at 14:08
  • KML isn't just a vector format; that's the misunderstanding here. KML is often used for vector, but not in this case.
    – nmtoken
    Jan 17, 2020 at 9:08

Try the WFS version (Web Feature Service)


Source: http://www.azgs.az.gov/services_azgeomap.shtml

or convert the Vector KML files to Shapefile

KML to Shape http://www.zonums.com/online/kml2shp.php

  • Thanks for finding the arizona dataset but I am actually more interested in the Nationwide map provided by the WMS through OneGeology... and the rest of the world.
    – GeoPy
    Sep 7, 2012 at 13:43

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