[gdal-dev] Is there a reference documentation for GDALMetadata structure?

[Andrea Aime]

Hi,
I was wondering if there is any documentation on what a GDALMetadata XML
structure might contain, both in terms
of element/attributes, and key names?

Online I've found this example:
https://www.awaresystems.be/imaging/tiff/tifftags/gdal_metadata.html

But checking some files I have laying around there is more variety, for
example:

<GDALMetadata>.
    <Item name="Band_1">Max Band_1</Item>.
    <Item name="Band_2">Min Band_1</Item>.
    <Item name="Band_3">Mean Band_1</Item>.
    <Item name="Band_4">SD Band_1</Item>.
    <Item name="Band_5">MASD Band_1</Item>.
    <Item name="Band_6">Valid Inputs</Item>.
    <Item name="OFFSET" sample="0" role="offset">0</Item>.
    <Item name="SCALE" sample="0"
role="scale">0.000100000000000000005</Item>.
    <Item name="OFFSET" sample="1" role="offset">0</Item>.
    <Item name="SCALE" sample="1"
role="scale">0.000100000000000000005</Item>.
    <Item name="OFFSET" sample="2" role="offset">0</Item>.
    <Item name="SCALE" sample="2"
role="scale">0.000100000000000000005</Item>.
    <Item name="OFFSET" sample="3" role="offset">0</Item>.
    <Item name="SCALE" sample="3"
role="scale">0.000100000000000000005</Item>.
    <Item name="OFFSET" sample="4" role="offset">0</Item>.
    <Item name="SCALE" sample="4"
role="scale">0.000100000000000000005</Item>.
    <Item name="OFFSET" sample="5" role="offset">0</Item>.
    <Item name="SCALE" sample="5"
role="scale">0.000100000000000000005</Item>.
</GDALMetadata>.

but also:

<GDALMetadata>.
    <Item name="lat#units">degrees_north</Item>.
    <Item name="LatLon_Projection#earth_radius">6371229</Item>.
    <Item
name="LatLon_Projection#grid_mapping_name">latitude_longitude</Item>.
    <Item name="lon#units">degrees_east</Item>.
    <Item
name="NC_GLOBAL#Analysis_or_forecast_generating_process_identifier_defined_by_originating_centre">Coastal
Ocean Circulation Model</Item>.
    <Item name="NC_GLOBAL#Conventions">CF-1.6</Item>.
    <Item name="NC_GLOBAL#featureType">GRID</Item>.
    <Item name="NC_GLOBAL#file_format">GRIB-2</Item>.
    <Item name="NC_GLOBAL#GRIB_table_version">2,1</Item>.
    <Item name="NC_GLOBAL#history">Read using CDM IOSP GribCollection
v3</Item>.
    <Item name="NC_GLOBAL#Originating_or_generating_Center">US National
Weather Service, National Centres for Environmental Prediction
(NCEP)</Item>.
    <Item name="NC_GLOBAL#Originating_or_generating_Subcenter">0</Item>.
    <Item name="NC_GLOBAL#Type_of_generating_process">Forecast</Item>.
    <Item name="NETCDF_DIM_EXTRA">{time}</Item>.
    <Item name="NETCDF_DIM_time_DEF">{1,6}</Item>.
    <Item name="NETCDF_DIM_time_VALUES">3</Item>.
    <Item name="time#calendar">proleptic_gregorian</Item>.
    <Item name="time#long_name">GRIB forecast or observation time</Item>.
    <Item name="time#standard_name">time</Item>.
    <Item name="time#units">Hour since 2014-01-23T00:00:00Z</Item>.
    <Item name="u-component_of_current_surface#abbreviation">UOGRD</Item>.
    <Item name="u-component_of_current_surface#coordinates">reftime time
lat lon </Item>.
    <Item
name="u-component_of_current_surface#Grib2_Generating_Process_Type">Forecast</Item>.

    <Item name="u-component_of_current_surface#Grib2_Level_Type">Ground or
water surface</Item>.
    <Item
name="u-component_of_current_surface#Grib2_Parameter">{10,1,2}</Item>.
    <Item
name="u-component_of_current_surface#Grib2_Parameter_Category">Currents</Item>.

    <Item
name="u-component_of_current_surface#Grib2_Parameter_Discipline">Oceanographic
products</Item>.
    <Item
name="u-component_of_current_surface#Grib2_Parameter_Name">u-component of
current</Item>.
    <Item
name="u-component_of_current_surface#Grib_Variable_Id">VAR_10-1-2_L1</Item>.

    <Item
name="u-component_of_current_surface#grid_mapping">LatLon_Projection</Item>.

    <Item name="u-component_of_current_surface#long_name">u-component of
current @ Ground or water surface</Item>.
    <Item name="u-component_of_current_surface#missing_value">nan</Item>.
    <Item name="u-component_of_current_surface#units">m/s</Item>.
    <Item name="abbreviation" sample="0">UOGRD</Item>.
    <Item name="coordinates" sample="0">reftime time lat lon </Item>.
    <Item name="Grib2_Generating_Process_Type" sample="0">Forecast</Item>.
    <Item name="Grib2_Level_Type" sample="0">Ground or water
surface</Item>.
    <Item name="Grib2_Parameter" sample="0">{10,1,2}</Item>.
    <Item name="Grib2_Parameter_Category" sample="0">Currents</Item>.
    <Item name="Grib2_Parameter_Discipline" sample="0">Oceanographic
products</Item>.
    <Item name="Grib2_Parameter_Name" sample="0">u-component of
current</Item>.
    <Item name="Grib_Variable_Id" sample="0">VAR_10-1-2_L1</Item>.
    <Item name="grid_mapping" sample="0">LatLon_Projection</Item>.
    <Item name="long_name" sample="0">u-component of current @ Ground or
water surface</Item>.
    <Item name="missing_value" sample="0">nan</Item>.
    <Item name="NETCDF_DIM_time" sample="0">3</Item>.
    <Item name="NETCDF_VARNAME"
sample="0">u-component_of_current_surface</Item>.
    <Item name="units" sample="0">m/s</Item>.
    <Item name="UNITTYPE" sample="0" role="unittype">m/s</Item>.
</GDALMetadata>

The periods at the end of the line are not valid, not sure where they are
coming from, exiftool reports them out
of one tiff file I have handy, which was converted out of a grib file a few
years ago

Cheers
Andrea

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