NOTE: This page is work in progress.

OGC WMS Driver

Primary goal of the project is to allow remote access to geospatial image data using WMS protocol. The driver will be compatible at least with version 1.3.0, 1.1.1 and 1.1.0 specifications. Secondary goal is to allow remote access using other WMS-like or tile protocols including WMS-C, TMS, TileService.

Details

• server address and parameters via xml file and embedded in dataset name
  • complete information in xml file
    • example1.xml

      <GDAL_WMS_Driver>
        <Service name="WMS">
          <Version>1.3.0</Version>
          <ServerUrl>http://127.0.0.1/mapserv.cgi</ServerUrl>
          <CRS>CRS:83</CRS>
          <ImageFormat>image/png</ImageFormat>
          <Layers>layer1,layer2</Layers>
          <Styles>style1,style2</Styles>
          <DataWindow>
            <MinX>-180.0</MinX>
            <MaxX>180.0</MaxX>
            <MinY>-90.0</MinY>
            <MaxY>90.0</MaxY>
            <ResolutionX>0.01</ResolutionX>
            <ResolutionY>0.01</ResolutionY>
          </DataWindow>
          <DataAccess type="tiled">
            <OriginX>-180.0</OriginX>
            <OriginY>-90.0</OriginY>
            <TileSizeX>256</TileSizeX>
            <TileSizeY>256</TileSizeY>
          </DataAccess>
        </Service>
        <Cache>
          <Path>/tmp/example1_cache</Path>
        </Cache>
      </GDAL_WMS_Driver>
      

    • dataset name

      WMS:example1.xml
      

  • minimal information in xml file (other values extracted from GetCapabilities response / defaults)
    • example2.xml

      <GDAL_WMS_Driver>
        <Service name="WMS">
          <ServerUrl>http://127.0.0.1/mapserv.cgi</ServerUrl>
          <Layers>layer1,layer2</Layers>
        </Service>
      </GDAL_WMS_Driver>
      

    • dataset name

      WMS:example2.xml
      

  • minimal information in xml file, layers selection in dataset name
    • example3.xml

      <GDAL_WMS_Driver>
        <Service name="WMS">
          <ServerUrl>http://127.0.0.1/mapserv.cgi</ServerUrl>
        </Service>
      </GDAL_WMS_Driver>
      

    • dataset name

      WMS:example3.xml:Service,Layers=layer1,layer2,layer3
      

• issue and parse GetCapabilities requests
  • provide simplified human-readable version for gdalinfo
  • store layer/style name, description, legend url, etc. in GDAL dataset meta-data fields

• two image data access methods
  • tiled: data is requested in small blocks, cached
  • immediate: one request per RasterIO call, not cached

External links

• ​OGC WMS Specification
• ​TMS Specification
• ​WMS Tiling Client Recommendation

People

• Adam Nowacki (student)
  • email nowak@…
  • talk using irc.freenode.net, channel #gdal, nick Nowak
• Daniel Morissette (mentor)