[netcdfgroup] Spatial subset using NcML...

• To: <netcdfgroup@xxxxxxxxxxxxxxxx>
• Subject: [netcdfgroup] Spatial subset using NcML...
• From: <Garth.Warren@xxxxxxxx>
• Date: Mon, 18 Apr 2011 09:46:45 +1000

Hello all:

I am using NcML to aggregate many hundreds of netCDF files. My data is 
regularly gridded continental (Australian) daily interpolated rainfall. The 
dimensions of these files are:

Lat = 681
Lon = 841
Time = 1

I am able to aggregate the existing rainfall files using the following simple 
NcML:

<?xml version="1.0" encoding="utf-8"?>
<netcdf xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"; 
xmlns:xsd="http://www.w3.org/2001/XMLSchema"; 
xmlns="http://www.unidata.ucar.edu/namespaces/netcdf/ncml-2.2";>
  <aggregation type="joinExisting" dimName="time">
    <scan location="\rain\2011\" suffix=".nc" subdirs="false" 
dateFormatMark="#yyyyMMdd" />
  </aggregation>
</netcdf>

In the example above I have 48 netCDF files in the directory '/rain/2011/'. 
This code is working, however in addition to aggregating these files we also 
need to be able to apply a spatial subset.

Specifically we would like to get the aggregated data as 1*1 degree tiles, this 
would equate to 20*20 (400) rainfall cells, rather than the full ~600 000 
cells. Ideally we would like to be able to specify a 'bounding box' type of 
subset by setting a lat/lon range. Is this possible in NcML? We would like to 
use NcML as the 'interface' to our netCDF data. I've spent hours on the unidata 
site to no avail so any help would be greatly appreciated.

I've attached some example data.

Kind regards,

Garth

Attachment: 20110104_rain_s1102.nc
Description: 20110104_rain_s1102.nc

Attachment: 20110103_rain_s1102.nc
Description: 20110103_rain_s1102.nc

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  • Re: [netcdfgroup] Spatial subset using NcML...
    • From: John Caron