Trying to use gdal_translate on WMS

Question

I am trying to export a raster image from a WMS using gdal_translate and have not had any success. I have read http://www.gdal.org/frmt_wms.html but still no success. In my XML file, what should the values for SizeX and SizeY represent?

Here is the command line parameters: gdal_translate -of JPEG -outsize 500 250 ac3.xml ac3.jpg.

Error Message: Input file size is 2666666, 1333333 0ERROR 1: GDALWMS: The server returned unknown exception. ERROR 1: ac3.xml, band 1: IReadBlock failed at X offset 0, Y offset 0

Here is my ac3.xml:

<GDAL_WMS>
<Service name="WMS">
<Version>1</Version>
<ServerUrl>http://data1.commons.psu.edu/arcgis/services/pasda/AlleghenyCountyImagery2010/MapServer/WMSServer?</ServerUrl>
<Layers>AlleghenyCountyImagery2010</Layers>
</Service>
<DataWindow>
<UpperLeftX>-80.413955</UpperLeftX>
<UpperLeftY>40.717648</UpperLeftY>
<LowerRightX>-79.641264</LowerRightX>
<LowerRightY>40.153982</LowerRightY>
<SizeX>2666666</SizeX>
<SizeY>1333333</SizeY>
</DataWindow>
<Projection>EPSG:4326</Projection>
<BlockSizeX>256</BlockSizeX>
<BlockSizeY>256</BlockSizeY>
</GDAL_WMS>

Answer 1

You must look at the GetCapabilities of that server. The layer name is not "AlleghenyCountyImagery2010" but it is "0". Edit that into your XML file and your gdal_translate command will work.

SizeX and SizeY comes from extents and native resolution of the WMS service. If the site is 100 km wide and resolution is 1 m/pixel then SizeX is 100000.