Re: Scale factor and offset problem

Hi John

Thanks for you answer.

In some cases, I need to unpack and repack data, because I need to extract data according to user's crtiteria, among others, data value ( ie temperature between 10 and 30).

I use NetcdfDataset.acquireDataset() for performance as described in documentation.

I also could use NetcdfDataset.openDataset() with "enhance" parameter set to false, but I need to add Coordinate Systems, that's also why I use the "enhance" flag to true (acquireDataset() or openDataset()).


At 18:05 19/06/2007, John Caron wrote:
Hi Didier:

Is there some reason to unpack and repack?

If you open with NetcdfDataset.openFile() it will not get unpacked - you will have the original variable and data.


Didier Earith wrote:
Hi all,
I have a problem with scale factor and offset when I use th netcdf java API (v2.2.20). I have to extract netcdf variables with scale_factor and offset attributes and write the results as another netcdf file. The NetcdfDataset class automatically deals with scale_factor and offset attributes when it opens dataset, and that's right (but it removed scale_factor and add_offset attributes) But when I want to write variables into another netcdf file, I need to have the data type, the scale factor and offset values of the original variables to packed data again.
The VariableDS class provides a public getOriginalDatatype API, that's OK.
But scale factor and offset attribute of the VariableDS class are private and there is no API get them. I saw the getOriginalVariable in the VariableDS class which return the original variable with the scale_factor and add_offset attributes. But unfortunately, this API is not visible (private) :
 ucar.nc2.Variable getOriginalVariable() {
    *return* orgVar; // proxy.getOriginalVariable();
So, how can I get the scale factor and offset values with netcdf java API to pack again the variables.

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