Although the spec doesnt explicitly say so (as far as i can tell), apparently a "scale factor" is a sign bit, then a 15-bit integer. Apparently the formula is result = value * 10^-scale. Its frustrating that the spec is so poorly written - but if you see it documented somewhere, please send me a reference. I will fix this asap. thanks! John > Hi John, > > Yes, it would appear that the signing of the scale factor is the issue. > Using wgrib2, I see the following: > > lvl1=100 scale=-2 val=925 > > Given that Isobaric surface is in Pa, that would seem correct that 925x10^-2 > should be 92500. > > So, is the reading of the sign of the scale factor an issue in Grib2NetCDF or > is that an incorrect usage of the scale factor? These grib2 files are coming > from the Canadian Weather Office so I would hope that they are providing them > correctly? > > Thanks for looking into this, > -Edward > > ________________________________________ > From: Unidata netCDF Java Support address@hidden > Sent: Saturday, 29 October 2011 11:28 a.m. > To: Edward Glen > Subject: [netCDFJava #HNY-858397]: Grib2NetCDF converts pressure level 925hPa > to 9.25e-128 > > Hi Edward: > > Im seeing in the PDS for that GRIB record: > > Type of first fixed surface == 100 (table 4.5: Isobaric surface) > Scale factor of first fixed surface == 130 > Scaled value of first fixed surface == 925 > > so i end up with 925 x 10^130 which apparently overflows. > > im guessing this should be 9.25 x 10-2, ie the scale factor should be > considered signed ?? > > do you see a different value in another software package ? > > John > > > Full Name: Edward Glen > > Email Address: address@hidden > > Organization: MetService New Zealand > > Package Version: toolsUI-4.2 > > Operating System: Ubuntu > > Hardware: > > Description of problem: > > > > I used the ucar.nc2.iosp.grib.Grib2Netcdf converter to convert the > > attached .grib2 file to NetCDF (result also attached). As can be seen, > > the resulting netCDF file encodes the pressure level as 9.25e-128. > > Can anyone shed some light as to why/how this is happening and what > > (if anything) I can do about it? > > > > Thanks, > > -Edward > > > > > > > Ticket Details > =================== > Ticket ID: HNY-858397 > Department: Support netCDF Java > Priority: Normal > Status: Open > > > Ticket Details =================== Ticket ID: HNY-858397 Department: Support netCDF Java Priority: Normal Status: Closed
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