[THREDDS #ETD-820941]: aggregation and datasetscan

• To: venus@xxxxxx
• Subject: [THREDDS #ETD-820941]: aggregation and datasetscan
• From: "Unidata THREDDS Support" <support-thredds@xxxxxxxxxxxxxxxx>
• Date: Mon, 11 Dec 2006 16:29:48 -0700

Hi Valentijn,

> thanks for your work. can you send us an example of how ncml aggreagtion
> over time could work for the OpenDAP server that worked:
>http://www.cooa.unh.edu/opendap/nph-dods/webcoast/dods_data/COOA_Satellite_Data_Products/

I took a look at this dataset. Not being very familiar with this dataset, I 
didn't dig too much into which datasets would make sense to aggregate together. 
However, I did run into a problem even accessing the data from within the 
netCDF-java library. I think it has to do with how the various layers deal with 
variable names. In the case I was looking at one of the variable containers was 
called "Data Fields. The problem is that the netCDF layer doesn't like spaces 
in variable names so it encodes it as an underscore ("_"). When I tried to ask 
for the data the netCDF-java layer did not succeed. I think it has to do with 
this variable name encoding. I'm double checking with John Caron (who is out of 
town for a few days) on this.


However, I looked at the Pathfinder data from earlier in this ticket and got an 
aggregation working. Here is the catalog I put together:

<?xml version="1.0" encoding="UTF-8"?>
<catalog xmlns="http://www.unidata.ucar.edu/namespaces/thredds/InvCatalog/v1.0"; 
xmlns:xlink="http://www.w3.org/1999/xlink";
         version="1.0.1" >

  <service name="thisDODS" serviceType="OPENDAP" base="/thredds/dodsC/" />

  <dataset name="valentijn's agg of UNH data" ID="valentijn" 
urlPath="valentijnAggOfUNH">
    <metadata>
      <serviceName>thisDODS</serviceName>
      <dataType>Grid</dataType>
    </metadata>
    <netcdf xmlns="http://www.unidata.ucar.edu/namespaces/netcdf/ncml-2.2";>
      <variable name="time">
        <attribute name="_CoordinateAxisType" type="String" value="Time" />
      </variable>
      <variable name="lat">
        <attribute name="_CoordinateAxisType" type="String" value="Lat" />
      </variable>
      <variable name="lon">
        <attribute name="_CoordinateAxisType" type="String" value="Lon" />
      </variable>
      <variable name="dsp_band_1">
        <attribute name="_CoordinateAxes" type="String" value="time lat lon" />
      </variable>
      <aggregation dimName="time" type="joinNew">
        <variableAgg name="dsp_band_1" />
        <netcdf 
location="http://dods.gso.uri.edu/dods-3.4/nph-dods/Pathfinder/Northwest_Atlantic/6km/declouded/1999/1/f99001082417.hdf";
 
                coordValue="1999-01-01T08:24:17Z" />
        <netcdf 
location="http://dods.gso.uri.edu/dods-3.4/nph-dods/Pathfinder/Northwest_Atlantic/6km/declouded/1999/1/f99001181038.hdf";
 
                coordValue="1999-01-01T18:10:38Z" />
        <netcdf 
location="http://dods.gso.uri.edu/dods-3.4/nph-dods/Pathfinder/Northwest_Atlantic/6km/declouded/1999/1/f99001195049.hdf";
 
                coordValue="1999-01-01T19:50:49Z" />
        <netcdf 
location="http://dods.gso.uri.edu/dods-3.4/nph-dods/Pathfinder/Northwest_Atlantic/6km/declouded/1999/1/f99002081244.hdf";
 
                coordValue="1999-01-02T08:12:44Z" />
        <netcdf 
location="http://dods.gso.uri.edu/dods-3.4/nph-dods/Pathfinder/Northwest_Atlantic/6km/declouded/1999/1/f99002180018.hdf";
 
                coordValue="1999-01-02T18:00:18Z" />
      </aggregation>
    </netcdf>
  </dataset>

</catalog>

The various "_Coordinate*" attributes make the dataset recognizable as a Grid 
dataset to the ToolsUI.

Hope this helps.
Let me know if you have any more questions.

Ethan

Ticket Details
==================
Ticket ID: ETD-820941
Department: Support THREDDS
Priority: Critical
Status: Open