CODEWITHSUNDEEP
netcdfthreddsncml
Sia
Sia

Reputation: 207

NcML aggregation of remote THREDDS catalog

I want to aggregate all files within a specific directory of a remote THREDDS catalog. These are grib2 files for nam forecast. This is the main list of directories for each month. Here is my ncml file for the aggregation of this catalog of files:

<?xml version="1.0" encoding="UTF-8"?>
<netcdf xmlns="http://www.unidata.ucar.edu/namespaces/netcdf/ncml-2.2" >
    <aggregation dimName="time" type="joinExisting">
    <scan location="http://www.ncei.noaa.gov/thredds/dodsC/nam218/201807/20180723/" regExp="^.*\.grb2$" subdirs="false"/>
    <dimension name="time" orgName="t" />
    </aggregation>
</netcdf>

Also, I am mostly interested in having these two variables in the files: u-component_of_wind_height_above_ground and v-component_of_wind_height_above_ground.

I am not sure the above aggregation is correct from the remote catalog. I get this error from the above ncml file:

There are no datasets in the aggregation DatasetCollectionManager{ collectionName='http://www.ncei.noaa.gov/thredds/dodsC/nam218/201807/20180723/^.*\.grb2$' recheck=null dir=http://www.ncei.noaa.gov/thredds/dodsC/nam218/201807/20180723/ filter=^.*\.grb2$

How this ncml file should be written?

Thanks.

Upvotes: 0

Views: 393

Answers (2)

David
David

Reputation: 825

You can write a simple program (I used c++) for use in the command prompt. (I use Windows.) It launches a BAT file that launches wget and downloads the latest THREDDS catalog, then saves it in plain text, then the c++ program loads the entire file into a string where I parse it and do what I want with the data.

Upvotes: 0

Rich Signell
Rich Signell

Reputation: 16385

You cannot glob remote URLs so you will need to provide a list of these OPeNDAP endpoints to the aggregation, like:

<dataset name="Nam218" urlPath="nam218">
  <netcdf xmlns="http://www.unidata.ucar.edu/namespaces/netcdf/ncml-2.2">
    <aggregation dimName="time" type="joinExisting">
      <netcdf location="http://www.ncei.noaa.gov/thredds/dodsC/nam218/201807/20180723/<file01>.grb2"/>
      <netcdf location="http://www.ncei.noaa.gov/thredds/dodsC/nam218/201807/20180723/<file02>.grb2"/>
      <netcdf location="http://www.ncei.noaa.gov/thredds/dodsC/nam218/201807/20180723/<file03>.grb2"/>
    </aggregation>
  </netcdf>
</dataset>

Upvotes: 2

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