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Tracing WMS Calls

Occasionally you will have trouble connecting to a WMS service; here is how to enable tracing.

Traceing WMS Requests

  1. Please use the the provided .options File. The ”.options” file should be dropped into you uDig folder to enable additional tracing information.

    • Create the following file:


      #Master Tracing Options
      #Tue Aug 05 14:56:31 PDT 2008
    • Place it in your uDig folder (next to your udig.exe file):

      C:\Program Files\uDig\1.1\eclipse

  2. Now when you restart uDig additional messages will be added to your log. These messages show the Requests sent to the WMS service.

  3. Check the log for tracing information

Example Tracing Information

When connecting to the JPL server and choosing the blue marble layer the following trace was produced:

!ENTRY net.refractions.udig.catalog.internal.wms 4 0 2008-09-05 08:26:15.561
 !MESSAGE GetCapabilities: `http://wms.jpl.nasa.gov/wms.cgi?REQUEST=GetCapabilities&VERSION=1.1.1&SERVICE=WMS`_

!ENTRY net.refractions.udig.catalog.internal.wms 4 0 2008-09-05 08:26:24.781
 !MESSAGE GetMap: `http://wms.jpl.nasa.gov/wms.cgi?SERVICE=WMS&LAYERS=BMNG&EXCEPTIONS=application/vnd.ogc.se\_xml&FORMAT=image/png&HEIGHT=357&TRANSPARENT=TRUE&REQUEST=GetMap&BBOX=-180.0,-90.0,180.0,90.0&WIDTH=714&STYLES=default&SRS=EPSG:4326&VERSION=1.1.1 <http://wms.jpl.nasa.gov/wms.cgi?SERVICE=WMS&LAYERS=BMNG&EXCEPTIONS=application/vnd.ogc.se_xml&FORMAT=image/png&HEIGHT=357&TRANSPARENT=TRUE&REQUEST=GetMap&BBOX=-180.0,-90.0,180.0,90.0&WIDTH=714&STYLES=default&SRS=EPSG:4326&VERSION=1.1.1>`_

The URLs mentioned during tracing can be cut and pasted into a browser to verify an error message, or see the same image that uDig displayed.

Trouble Shooting a WMS Server

Please keep the following in mind when connecting to a WMS. The URL you provide should be a valid GetCapabilities URL with the following elements:

  • REQUEST=GetCapabilities: his is actually a requirement; uDig will supply it for you if needed.
  • SERVICE=WMS: this is also a requirement - many servers speak several protocols
  • VERSION=X.X.X: this is version of the WMS protocol you would like to use

The uDig will enter into “version negotiation” with the server using the above information.

  1. uDig will will request the GetCapabilities document with the above information
  2. The server will respond with a valid capabilities document that contains the “closest” version number the server can produce.
  3. Based on this response uDig may
    • Connect and ask you to choose a layer; or
    • Change the VERSION and try again ...


  1. right click on uDig.app and choose “Show Package Contents”
  2. Navigate to MacOS folder
  3. Next the the file udig_internal.ini create the file ”.options” as described above.

You can either review the application logs located (from the about udig screen); or start the application from the command line with:

udig.app/Contents/MacOS/udig_internal -consoleLog

Related tasks

View Error Log and Configuration Details

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