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WMS OPENDAP

The server can also read data remotely from an OpenDAP service. The same routine applies as given in Create a WMS service on a file, except that you have to provide an OpenDAP url.

For example:

<!-- Layer configuration -->
  <Layer type="database">
    <FilePath>http://opendap.nmdc.eu/knmi/thredds/dodsC/essence/run031/2D_3hrly/temp2_031_2006-2010.nc</FilePath>
    <Variable>temp2</Variable>
    <Styles>rainbow</Styles>
   <Dimension name="time" interval="PT3H" default="max">time</Dimension>
  </Layer>

After you have added a new dataset, you always need to do:

/data/software/adagucserver/bin/adagucserver --updatedb --config /data/services/config/newservice.xml

Some facts about Opendap

  • OPeNDAP is the name of the organization and the name of the protocol
  • Open-source Project for a Network Data Access Protocol
  • Data is stored at remote server
  • Data model is similar to NetCDF’s data model (with differences)
    • N-dimensional array container, with variables, dimensions and attributes
  • Only requested pieces of data are sent
    • Accessing small pieces of large files on a remote server can still be quick
    • Data is requested based on sub-setting along dimensions
  • OPeNDAP resources can be opened locally on your computer as if it were local files using the NetCDF library
    • Local files versus remote files is transparent
  • The concept of a file is gone, an OPeNDAP endpoint can represent thousands of files aggregated along a dimension
    • E.g. Usually concatenate a large time series observation to one endpoint using the time dimension