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

[Joaquim Luis]

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_gdalread.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"://geophysical_data/sst

(GMT syntax to access the subdataset), the calls to

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