[gdal-dev] Failure to fetch scale_factor and other on a subdataset of a L2 SST nc file (from OceanColor)

[Even Rouault]

Le mercredi 11 mai 2016 23:56:32, Joaquim Luis a écrit :
> Hi,
> 
> In GMT we have this chunk of code to read Band metadata
> 
> if (GDALGetRasterScale(hBand, &bSuccess) != 1 ||
> GDALGetRasterOffset(hBand, &bSuccess) != 0) {
> 	Ctrl->band_field_names[nBand].ScaleOffset[0] = GDALGetRasterScale (hBand,
> &bSuccess);
> 	Ctrl->band_field_names[nBand].ScaleOffset[1] = GDALGetRasterOffset(hBand,
> &bSuccess);
> }
> else {
> ...
> 
> http://gmt.soest.hawaii.edu/projects/gmt/repository/entry/trunk/src/gmt_gda
> lread.c#L452
> 
> and it works fine so far. However, when I use it on a SST L2 file from
> OceanColor (a netCDF4 file) as in
> 
> grdinfo
> A2016123140500.L2_LAC_SST.nc=gd?HDF5:"A2016123140500.L2_LAC_SST.nc"://geoph
> ysical_data/sst
> 
> (GMT syntax to access the subdataset), the calls to

In the above you use the HDF5 driver, not the netCDF one. As far as I can see, 
GetScale() is implemented in the netCDF driver, but not in the HDF5 one.

> 
> GDALGetRasterScale(hBand, &bSuccess)
> 
> and friends return no data (bSuccess == 0 and confirmed in a debugger).
> However, if add a temporary
> 
> 	char **papszMetadataBand = GDALGetMetadata(hBand, NULL);
> 	int i, nCounterBand = CSLCount(papszMetadataBand);
> 	for (i = 0; i < nCounterBand; i++)
> 		fprintf(stderr, "Meta %d\t%s\n", i, papszMetadataBand[i]);
> 
> than the band's metadata is printed correctly (same info as that printed
> with gdalinfo).
> 
> Question: is this what it looks, a bug?
> 
> Thanks
> 
> Joaquim
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