[gdal-dev] Extending GDAL Color Interpretation enumeration for infra-red bands (+ band wavelength) ?

[Javier Jimenez Shaw]

Hi Even,

My bias is towards agriculture drone images, that I was processing in my
current employer. To compute vegetation indices the "Central Wavelength"
and "FWHM" are the best definition. Different sensors have different
"types" of Red, Blue, NIR or LWIR. So I see these two numbers the best
option.
Regarding the units, micro vs nano meters, I do not have a strong opinion.
(nano looks nicer in visible range, micro in thermal range).

About the names (in addition to the wavelength and fwhm), I would not go
into the details like "green05". That is very specific to a certain
satellite, and will be obsolete immediately. I agree with more generic
names like pan, blue, green, red, rededge, nir, lwir, ...
(for agriculture I would say that if I have to choose 3 bands, "red,
rededge, nir" would give a lot of information. But of course, other bands
are also used)

In Pix4D, for the radiometric correction needed in the images, we defined
this XMP namespace years ago:
http://pix4d.com/camera/1.0/
There are "Xmp.Camera.CentralWavelength", "Xmp.Camera.WavelengthFWHM" and
"Xmp.Camera.BandName". I do not mean that we should do the same, but just
an example of how that information was important.

One question. The IMAGERY metadata is available only on TIF, or also in
other file formats like JPG? I mean without any sidecar.

Cheers,
Javier.

On Sat, 31 Aug 2024 at 16:22, Even Rouault via gdal-dev <
gdal-dev at lists.osgeo.org> wrote:

> Hi,
>
> The GDAL Color Interpretation enumeration is a good start, but is quite
> limited regarding band spectral properties with just Red, Green, Bland,
> and nothing for other band wavelengths, particularly for infra-red.
>
> I was looking a bit at the classifications at
> https://en.wikipedia.org/wiki/Infrared#Regions , and there are several
> ones, like the "commonly used subdivision scheme" (NIR, SWIR, MWIR,
> LWIR, FIR) or "CIE division scheme" (IR-A, IR-B, IR-C) or "ISO 20743
> scheme" (NIR, MIR, FIR).
>
> My inclination would rather to re-use the STAC EO classification at
> https://github.com/stac-extensions/eo?tab=readme-ov-file#common-band-names,
>
> which shows a lot of similarities with
>
> https://github.com/awesome-spectral-indices/awesome-spectral-indices#expressions
> , and has a nice mapping with a few popular instruments.
>
> While we are it, should we standardize central wavelength and full width
> half max (FWHM), has special properties of a bands rather than generic
> text-based metadata, like:
>
> double GDALRasterBand::GetCentralWaveLengthMicrometer() -> NaN if unknown
> double GDALRasterBand::GetFWHMMicrometer() -> NaN if unknown
> void GDALRasterBand::SetCentralWaveLengthMicrometer(double)
> void GDALRasterBand::SetFWHMMicrometer(double)
>
> Or maybe just standardize a "CENTRAL_WAVELENGTH" and "FWHM" metadata
> items in the "IMAGERY" metadata domain:
>
> https://gdal.org/en/latest/user/raster_data_model.html#imagery-domain-remote-sensing
> ?
>
> Thoughts?
>
> Even
>
> --
> http://www.spatialys.com
> My software is free, but my time generally not.
>
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>
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