Re: [netcdf-java] combining and writing geogrids



Christopher Mueller wrote:
Greetings all,

I’m curious if anyone out there can help me with some questions I have about GeoGrids. Specifically I’m wondering if anyone knows how I can go about the process of combining multiple GeoGrids into one “object” and then write that object to a local .nc file. Thus far, I’ve succeeded in connecting to an opendap server, getting a single geogrid, subsampling it and using the GeoGrid.writeFile() method to create a local file. I’ve noticed that the javadoc for GeoGrid says not to use the writeFile method – but I couldn’t see another way of getting the data to disk.

So my first question is – what is the correct method for writing the contents of a GeoGrid to a local file?? I’ve checked out NetcdfFileWriteable, but that doesn’t allow me to add a GeoGrid (at least not directly).

ucar.nc2.dt.grid.NetcdfCFWriter is a helper class that replaces 
grid.writeFile(). It writes CF compliant files. It's still a bit rough but 
probably will work for you.


My second question is – is there a way to combine multiple geogrids so that their contents can be written to a single file. For example – if my opendap dataset has U, V, and Temp variables, I’d like them all to be written to a single file. My geogrid.writeFile method produces a dataset for each at this point

As you will see from the API, you have to construct a ucar.nc2.dt.GridDataset 
object. You can do this from an opendap dataset, just like any other dataset, 
see ucar.nc2.dt.grid.GridDataset.open(). If you dont want all the Geogrids, you 
will have to remove the ones you dont want. It should work, but we havent 
tested that particular case.


In relation to this second question – how would I combine geogrids from 2 separate opendap sources – assuming that they are identical aside from the variable(s) of interest?

Again, you would construct a ucar.nc2.dt.GridDataset and use NetcdfCFWriter to 
write it out. It may be tricky to get the GridDataset right, we've never 
attempted to combine from 2 different sources.


Thank you in advance for your help – it’s most appreciated.

good luck!


Chris

*Christopher Mueller/  /*|  Scientist

Applied Science Associates

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