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Step-by-step guide
Let's say you do not don't care about the GRIB data values (and its bitmap) and only want to keep the meta-data, for example when preparing a sample file (Also see Can I use my own GRIB/BUFR sample files - ecCodes GRIB and BUFR FAQ)
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Here we set all the field values to zero (-d0) in effect making it a constant field. Also if the input had a bitmap, it will be removed.
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