WCS Tutorial on Serving Data

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A work in progress that is not little more than notes.

Here's an NcML file that will take the tried and true COADS Climaology file and add enough metadata for the WCS service to build a valid coverage:

<?xml version="1.0" encoding="UTF-8"?>
<netcdf location="/data/nc/coads_climatology.nc" xmlns="http://www.unidata.ucar.edu/namespaces/netcdf/ncml-2.2">
 
  <attribute type="Structure" name="NC_GLOBAL">
    <attribute type="String" name="Conventions" value="CF-1.0"/>
  </attribute>
 
  <!-- We could use UDD metadata instead of this. -->
  <attribute name="WcsMetadata" type="OtherXML">
    <Domain xmlns="http://www.opengis.net/wcs/1.1" xmlns:ows="http://www.opengis.net/ows/1.1" xmlns:gml="http://www.opengis.net/gml">
      <SpatialDomain>
	<ows:BoundingBox crs="urn:ogc:def:crs:EPSG::4326">
	  <ows:LowerCorner>0 -90</ows:LowerCorner>
	  <ows:UpperCorner>360 90</ows:UpperCorner>
	</ows:BoundingBox>
      </SpatialDomain>
      <TemporalDomain>
	<TimePeriod>
	  <BeginPosition>2002-07-01T09:00/15:00</BeginPosition>
	  <EndPosition>2002-07-31T15:00/21:00</EndPosition>
	  <TimeResolution>6 hours</TimeResolution>
	</TimePeriod>
      </TemporalDomain>
    </Domain>
   <!--  <SupportedCRS xmlns="http://www.opengis.net/wcs/1.1">urn:ogc:def:crs:EPSG::4326</SupportedCRS> -->
  </attribute>
 
  <variable name="SST">
    <variable name="COADSX">
      <attribute name="standard_name" type="String" value="longitude"/>
    </variable>
 
    <variable name="COADSY">
      <attribute name="standard_name" type="String" value="latitude"/>
    </variable>
 
    <variable name="TIME">
      <attribute name="standard_name" type="String" value="time"/>
    </variable>
  </variable>
 
 <variable name="AIRT">
    <variable name="COADSX">
      <attribute name="long_name" type="String" value="longitude"/>
    </variable>
 
    <variable name="COADSY">
      <attribute name="long_name" type="String" value="latitude"/>
    </variable>
 
    <variable name="TIME">
      <attribute name="long_name" type="String" value="time"/>
    </variable>
  </variable>
 
</netcdf>

Here's a note from Benno about using UDD metadata in place of the cumbersome WcsMetadata element:

UDD is my abbreviation, actually you need to say "Unidata Dataset Discovery v1.0", which is far longer than I will ever remember.
The conventions registry is at http://xml.opendap.org/ontologies/NetcdfConventionRegistry.owl

which connects the ontology files describing the conventions to the strings that identify the convention in the Conventions tag
We have an example of using UDD. http://test.opendap.org:8090/ioos/mday_joinExist.ncml which has metadata that expands to http://iridl.ldeo.columbia.edu/cgi-bin/view/browse2.pl?node=http%3A%2F%2Ftest.opendap.org%3A8090%2Fioos%2Fmday_joinExist.ncml&repository=opendap1-owl

Benno