Units

Original Goal

To add some notation of units to the metadata.json file.

There are standards for units - but several of them

units should be machine readable, so we need a standard
the standard should include the derived units we need to express
the standard should be acceptable to tools/languages that will want to read the data
- Python and R
- collaborators like Catalyst

Things to look at:

UDUNITS2
- https://cran.r-project.org/web/packages/units/vignettes/measurement_units_in_R.html says works in R
  - " udunits on the other hand is the units standard of choice by the climate science community, and is adopted by the CF (Climate and Forecast) conventions, which mostly uses NetCDF"
- there are python language packages too
pint
- is python for sure but R = ??
- used by Catalyst and Datacette. Well, maybe not
UCUM Unified Code for Units of Measure is maybe dead?
- that R ref says "... links seem to be dead. UCUM is the preferred encoding for standards from the Open Geospatial Consortium"
https://cf-xarray.readthedocs.io/en/latest/units.html extends pint to be like UDUNITS1
https://github.com/frictionlessdata/specs/issues/216 and also https://github.com/frictionlessdata/specs/issues/537
https://www.qudt.org/doc/DOC_VOCAB-UNITS.html
- QUDT is a non-profit charity that is derived from the NASA Exploration Initiatives Ontology Models (NExIOM) project.
- it is under active development
- java libraries. https://github.com/eigendude/pyqudt is 4 years old. But it is RDF and JSON so we might be able to work something out.
https://github.com/annotated-types/annotated-types?tab=readme-ov-file#unit that would annotate a value
- "Please note that annotated_types itself makes no attempt to parse or validate the unit string in any way. That is left entirely to downstream libraries, such as pint or astropy.units."

Because the choice of standard was unclear, Ian just picked one from R