Possibility to filter by cloud cover?

[jerstlouis]

It would be great if Earth Search (e.g., endpoint at https://earth-search.aws.element84.com/v1) would support the ability to filter by cloud cover, ideally using an OGC API - Features - Part 3: Filtering and a CQL2-Text filter query parameter (e.g., filter=eo:cloud_cover < 30).

Notably, the queryables end-point usually associated with filtering (at least for Features) at https://earth-search.aws.element84.com/v1/collections/sentinel-2-l2a/queryables already includes eo:cloud_cover.

Currently, the work-around for this lack of functionality is to sort by ascending cloud cover and stop paging items after reaching the maximum acceptable cloud cover.

This missing capability was noticed in OGC Testbed 20 GeoDataCubes (as well as previous OGC innovation initiatives) and is discussed in an upcoming Engineering Report (OGC 24-035).

[ircwaves]

@jerstlouis -- only recently did the CQL2 JSON make its way into stac-server (which Earth Search uses), so it would be good to get an upgrade of the stac-server for that. I'm not sure how much of a lift CQL2 TEXT would be, but I'm sure PRs are welcome on the stac-server repo.

[ircwaves]

@jerstlouis -- Another work around is to use the query extension implementation:

[icooke] src/earthsearch (git)-[update-sentinel2-to-stac-image] % \
  stac-client search  https://earth-search.aws.element84.com/v1/ \
    --collection sentinel-2-c1-l2a \
    --query "eo:cloud_cover<10" \
    --max-items 10 \
  | jq '.features[]|.properties."eo:cloud_cover"'
9.766189
3.966558
2.923066
0.091871
9.998482
5.805432
2.015412
6.686127
0.228114
2.221058

[jerstlouis]

Thanks @ircwaves . It's quite difficult to make the mapping between the the conformance declaration and the actual STAC query extension.

Which conformance entry corresponds to this STAC query? Is it https://api.stacspec.org/v1.0.0/ogcapi-features#query ?

Nothing at https://api.stacspec.org/v1.0.0/ogcapi-features/ seems to hint to the avaiability of that capability.

CQL2-JSON is a great start, and CQL2-JSON <-> CQL2-Text conversion is something for which we eventually plan to provide an open-source library, which could potentially be used if no one has yet implemented this in STAC server by the time this is ready.

[ircwaves]

Which conformance entry corresponds to this STAC query? Is it https://api.stacspec.org/v1.0.0/ogcapi-features#query ?

pystac-client is checking for conformance with [item-search#query](https://api.stacspec.org/v1.0.0/item-search#query). Which jives with the 3rd paragraph in the extension README.

Nothing at https://api.stacspec.org/v1.0.0/ogcapi-features/ seems to hint to the avaiability of that capability.

Yeah, there's some note in that direction here.

... we eventually plan to provide an open-source library, ...

I'll keep an eye out for that library, should it be carved out.

[jerstlouis]

pystac-client is checking for conformance with item-search#query. Which jives with the 3rd paragraph in the extension README.

Unfortunately, the content of https://api.stacspec.org/v1.0.0/item-search/ hints at absolutely nothing related to the functionality described in that query extension README which talks about a query property in the payload for POST requests to /search. So this is very misleading at best (I was not able to figure that out). It would be great if following the conformance URIs would somehow point towards the relevant description of the extension.

[ircwaves]

Sorry I dropped our thread here. I often resort to CatSoT (Code as the Source of Truth), and inspected the stac-server code, along with the extension definition (https://github.com/stac-api-extensions/query). I'm flagging this for api-conformance updates, as you are correct that it should be easier to find.