[gdal-dev] HDF5 and geolocation arrays

[Michael Sumner]

This HDF5 (requires earthdata credentials your "Authorization: Bearer
<token>" in GDAL_HTTP_HEADERS, or equiv) presents without geolocation
arrays.

gdalinfo "/vsicurl/
https://n5eil01u.ecs.nsidc.org/AMSA/AU_SI12.001/2012.07.02/AMSR_U2_L3_SeaIce12km_B04_20120702.he5"
-sd 26
Driver: HDF5Image/HDF5 Dataset
Files: /vsicurl/
https://n5eil01u.ecs.nsidc.org/AMSA/AU_SI12.001/2012.07.02/AMSR_U2_L3_SeaIce12km_B04_20120702.he5
Size is 608, 896
Metadata:
  Conventions=CF-1.6
  HDFEOS_INFORMATION_HDFEOSVersion=HDFEOS_5.1.15
  history=This version of the Sea Ice processing code contains updates
provided by the science team on September 16, 2019. For details on these
updates, see the release notes provided in the DAP.
  institution=NASA's AMSR Science Investigator-led Processing System (SIPS)
  references=Please cite these data as: Markus, T., J. C. Comiso, and W. N.
Meier. 2018. AMSR-E/AMSR2 Unified L3 Daily 12.5 km Brightness Temperatures,
Sea Ice Concentration, Motion & Snow Depth Polar Grids, Version 1.
[Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice
Data Center Distributed Active Archive Center. doi:
https://doi.org/10.5067/RA1MIJOYPK3P.
  source=satellite observation
  title=AMSR-E/AMSR2 Unified L3 Daily 12.5 km Brightness Temperatures, Sea
Ice Concentration, Motion & Snow Depth Polar Grids
Corner Coordinates:
Upper Left  (    0.0,    0.0)
Lower Left  (    0.0,  896.0)
Upper Right (  608.0,    0.0)
Lower Right (  608.0,  896.0)
Center      (  304.0,  448.0)
Band 1 Block=608x1 Type=Int32, ColorInterp=Undefined
  Metadata:
    comment=data value meaning: 0 -- Open Water, 110 -- missing/not
calculated, 120 -- Land
    coordinates=lon lat
    long_name=Sea ice concentration daily average
    units=percent



gdalinfo --version
GDAL 3.9.0dev-cb4d30f56d, released 2024/04/15

The geolocation arrays are sds 33 and 32 respectively:

HDF5:"/vsicurl/
https://n5eil01u.ecs.nsidc.org/AMSA/AU_SI12.001/2012.07.02/AMSR_U2_L3_SeaIce12km_B04_20120702.he5
"://HDFEOS/GRIDS/NpPolarGrid12km/lon

HDF5:"/vsicurl/
https://n5eil01u.ecs.nsidc.org/AMSA/AU_SI12.001/2012.07.02/AMSR_U2_L3_SeaIce12km_B04_20120702.he5
"://HDFEOS/GRIDS/NpPolarGrid12km/lat

And things work when lining those up in VRT with warp. Can the HDF5 driver
be made to auto-detect these geolocation arrays?

I see that the NETCDF driver actually does:

gdalinfo "NetCDF:/vsicurl/
https://n5eil01u.ecs.nsidc.org/AMSA/AU_SI12.001/2012.07.02/AMSR_U2_L3_SeaIce12km_B04_20120702.he5"
-sd 26

I'm asking as an email rather than pursuing the fix because, these data are
actually a regular grid on the north and south poles, and so geolocation by
arrays is sub-optimal  the specification is listed in

https://nsidc.org/sites/default/files/au_si12-v001-userguide_1.pdf

and the two parameter sets are

Np-north: -te -3850000,  -5350000, 3750000, 5850000 -t_srs EPSG:3411
Sp-south: -te -3950000,  -3950000, 3950000, 4350000 -t_srs EPSG:3412

Is this generally something we should pursue within GDAL? It seems like an
endless task to detect-on-open exactly this situation and assign the easy
fix, but this is a pretty fundamental data stream and it's very common so
the longlat/arrays might be numerically detectable with other
heuristics hinting that it's polar (??) and there are plenty of other
sources that present equivalents in the right way e.g. this one:

"/vsicurl/
https://noaadata.apps.nsidc.org/NOAA/G02135/north/daily/geotiff/2012/07_Jul/N_20120702_concentration_v3.0.tif
"

The right approach is probably to inform the providers and get the right
metadata baked in ... but there's pros and cons to either. I'm not sure
there's even enough information in these files to clearly detect the
situation, it would be a bit like the NSIDCbin driver with its very strict
requirements.

Cheers, Mike


--

Michael Sumner
Software and Database Engineer
Australian Antarctic Division
Hobart, Australia
e-mail: mdsumner at gmail.com
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