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radiantearth / stac-spec

SpatioTemporal Asset Catalog specification - making geospatial assets openly searchable and crawlable
https://stacspec.org
Apache License 2.0
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Dataset periods not representable via ISO8601 #212

Closed simonff closed 5 years ago

simonff commented 6 years ago

In rare cases, a dataset has the period that cannot be represented in ISO8601. Two examples I've run into are CHIRPS pentads (http://chg-wiki.geog.ucsb.edu/wiki/CHIRPS_FAQ#How_does_CHIRPS_define_a_pentad.3F) and PDSI files (see https://www.northwestknowledge.net/metdata/data/early/2018/)

In both cases, there are multiple assets per month with duration 5 or 10 days, and the last asset covers the remainder - its duration varies from month to month.

m-mohr commented 6 years ago

ISO8601 was just a quick shot and I feared that there are strange values for periodicity out there. Not sure how we can handle that. Fall back to a simple string data type where you can put a description? That is the least desirable option though and we should try to find something better. How do other standards solve this? I think mostly with free text fields?!

cholmes commented 6 years ago

Yeah, I think the special cases just need a special extension.

I don't want to do something other than ISO8601 for the core, and the special cases can just use it in a crappy way. And then they can have their own way of representing the more advanced things.

m-mohr commented 5 years ago

Issue is outdated as we removed dataset periods from the collection spec. In data cube we now have a "step" field for temporal data, which allows ISO8601 for regular spaced steps and null for irregular steps. I'd say for other periods we need a custom field as Chris said.