[gdal-dev] Tag for units in GeoTIFF

[Javier Jimenez Shaw]

Thanks!

On Thu, 26 Oct 2023 at 12:27, Even Rouault via gdal-dev <
gdal-dev at lists.osgeo.org> wrote:

> Javier,
> Le 26/10/2023 à 11:59, Javier Jimenez Shaw via gdal-dev a écrit :
>
> Hi
>
> Using a GeoTIFF with a single band and float values can be very useful to
> show any distribution over the terrain. One typical example is DSM (digital
> surface model), where the value is the elevation on every point.
>
> Is there any standard (or accepted) metadata to say the units of those
> values?
>
> API wise in GDAL, you should use the GDALRasterBand::SetUnitType() to set
> the unit
>
> For TIFF, this will be encoded in the GDAL_METADATA TIFF tag like the
> following:
>
> <GDALMetadata>
>   <Item name="UNITTYPE" sample="0" role="unittype">foo</Item>
> </GDALMetadata>
>
> Regarding the value itself, it is mostly unspecified by GDAL. It could be
> a good practice to suggest to use strings recognized by the "udunits"
> package (when possible), like done in the netCDF CF conventions (
> http://cfconventions.org/Data/cf-conventions/cf-conventions-1.10/cf-conventions.html#units
> )
>
> Even
>
>
> In the typical case of DSM it is usually "meter" or "foot". But it can be
> something else, like "people/km2" for population, or "mm" for rain
> precipitation, or "kg/ha" for agricultural yield.
>
> Thanks
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