On 4/17/2011 5:46 PM, Garth.Warren@xxxxxxxx wrote:
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
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Hi Garth:
NcML does not do subsetting, that is typically done when you access the
data by only asking for the subset that you want. Also there is no
regridding capability.
If you use Netcdf-Java library, you can make subset requests in lat/lon
if the data can be read into a GridDataset object. Also, if you run a
THREDDS server, you can use the Netcdf Subset service to make requests
in lat/lon:
http://www.unidata.ucar.edu/projects/THREDDS/tech/tds4.2/reference/NetcdfSubsetService.html
John
