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The conversion from GRIB edition 1 (GRIB1) to edition 2 (GRIB2) is a format translation without any loss of information. Conversely the conversion from GRIB2 to GRIB1 is not always lossless because the edition 2 format has been extended to allow a wider set of scientific fields to be coded. Note: Converting to edition 1 is not supported.
Since the new GRIB2 format is going to replace GRIB1 we will focus more on the GRIB1 to GRIB2 conversion rather than the opposite, which sometimes is not possible.
The conversion algorithm should be easy to implement, but there are some factors making it challenging. First of all the new designed GRIB2 is in some points semantically different from GRIB1. Therefore it doesn't allow an easy mapping of the meaning across the two versions. Moreover some of the numeric code tables semantically identical are numerically different, which again doesn't allow an easy mapping between them, because the numeric codes for the same information element are different. We refer in particular to the type of level which is numerically different in the two editions.
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