What are the processing levels and where do they belong in STAC

[jeffnaus]

We should start reporting on the processing levels of our images. What are the processing levels and where should we report them. Is this one extension or is this additions to lots of extensions.

[jeffnaus]

Can we get direction from the ARD group about this?

[dlindenbaum]

Examples of different processing

• https://landsat.usgs.gov/landsat-processing-details

• https://sentinel.esa.int/web/sentinel/user-guides/sentinel-2-msi/processing-levels

• http://www.geo-rapp.org/wp-content/uploads/2014/12/GEOGLAM-RAPP-Campinas_Joao-Soares_INPE.pdf

[dlindenbaum]

As a second comment:

Should there be a processing extentension

[sjskhalsa]

a little history - processing levels for satellite data originated with CEOS, I believe, but were adopted by NASA - "To facilitate the discussion of data processing in practice, several processing levels were first defined in 1986 by NASA as part of its Earth Observing System and steadily adopted since then" (wikipedia). https://science.nasa.gov/earth-science/earth-science-data/data-processing-levels-for-eosdis-data-products

[matthewhanson]

There are no standard processing levels, everyone uses different nomenclature, and I really don't think there's any way we can hope to define a standard for that providers would use.

It makes more sense to have fields that specify units, or a flag for surface reflectance or atmospheric correction, or orthorectification, but even then I'm not sure how useful that is. Only if users were searching a catalog for specific types of data.

It seems more useful to use Datasets/Collections and have a good description of what the data is rather then trying to define a new set of standards for how data has been processed.

[jeffnaus]

I would go along with the idea of flags for "well know" processing steps like orthorectification and atmospheric correction and so on.

[fredliporace]

I've drafted something on the line that @jeffnaus suggested:

https://gist.github.com/fredliporace/217d1dbd59ff1ba633ce145f04a39d55

I'm in transit now, will detail later as I reach the office.

[fredliporace]

See https://github.com/radiantearth/stac-spec/issues/150 for related discussion

[cholmes]

Where are we going to put this? As some attribute on the asset / asset definition?

[fredliporace]

@cholmes I'm preparing a PR to the EO extension based on the draft above for further discussion. Note that I'll limit that to "Electro-optical" sensors, other sensors should probably have specific attributes defining their processing levels.

[m-mohr]

@matthewhanson wrote in #235:

@fredliporace I recently went to the ARD workshop this month at USGS, and this was one the things that was discussed.

It's just the start, but we've set up an ard-spec repo to start hashing out some sort of standards to describe processing as well as metrics for uncertainty.

If some standard fields come out of that effort, we can utilize those in STAC.

So I'm going to close this, feel free to post your ideas over in the ard-spec.