Re: [las_users] How to use NcML Aggregation with LAS

[Robert Fuller <rfuller@xxxxxxxxx>]

Hi,

We did this recently. Here is the answer from my colleagues Stephen 
Mulcahy who is not on this mailing list:

Howdy,

1. To create an ncml file for your files, you need to create an xml file 
like the following,

<netcdf xmlns="http://www.unidata.ucar.edu/namespaces/netcdf/ncml-2.2";>

<!-- example of aggregating multiple files into one -->
<aggregation dimName="TIME" type="joinExisting">
   <netcdf location="file:/romsdata/files/file_1.nc" />
   <netcdf location="file:/romsdata/files/file_2.nc" />
   <netcdf location="file:/romsdata/files/file_3.nc" />
   <netcdf location="file:/romsdata/files/file_4.nc" />
   <netcdf location="file:/romsdata/files/file_5.nc" />
 </aggregation>
</netcdf>

This aggregates the file_1.nc ... file_5.nc files together using the 
TIME dimension. There are various other ways of doing this aggregation - 
see http://www.unidata.ucar.edu/software/netcdf/ncml/v2.2/Aggregation.html

2. To publish an ncml file in THREDDS you need to add an entry like the 
following to your

<?xml version="1.0" encoding="UTF-8"?>
<catalog name="Test Catalog"

xmlns="http://www.unidata.ucar.edu/namespaces/thredds/InvCatalog/v1.0";
       xmlns:xlink="http://www.w3.org/1999/xlink";>

 <service name="TEST" serviceType="OpenDAP" base="/thredds/dodsC/" />
 <datasetRoot path="ROMS" location="/romsdata/files/"/>
 <dataset name="Test data" ID="roms1" serviceName="TEST" 
urlPath="ROMS/test.ncml"/>
</catalog>

This xml should be saved as catalog.xml in your THREDDS content 
directory. The ncml file should be in /romsdata/files/test.ncml

3. Finally, you need to add this to LAS using the addXML tool 
http://ferret.pmel.noaa.gov/LAS/documentation/installer-documentation/adding-gridded-data/the-addxml-utility 


See 
http://ferret.pmel.noaa.gov/LAS/documentation/installer-documentation/adding-gridded-data/using-addxml-on-a-netcdf-data-source 
for details of how to run addXML

-stephen
Rakesh Patil V. wrote:
> Hello there..
>
> I have a set of 763 NC files weekly SLA data.. right from oct 1992 to 
> May 2005.. I want to use them in My LAS.. After going through lot of 
> searches, i came to know that, Multiple NC files can be added into LAS 
> using "make.des"...
>
> I also came to know that there is most recommended way of getting time 
> series from all NC file using NcML Aggregations Concept in TDS.. Well, 
> i went thru the documentations, but i am unable to make out where we 
> have to write the NcML script.. After writing, by what extension the 
> file must be saved..??Then how to execute it..?? And finally, how to 
> link it with LAS..??
>
> I would appreciate ur quick reply.
>
> Thanks in advance.
>
> Regards
> Rakesh Patil
>
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