STAC collection conventions

Metadata required for entries in VEDA STAC to work with the VEDA Dashboard

Copied from veda-backend#29

Dashboard-specific notes that supplement the full stac-api collection specification. Note that there is no schema enforcement on the collection table content in pgstac—this provides flexibility but also requires caution when creating and modifying Collections.

Collection field, extension, and naming recommendations

Field &/or Extension	Recommendations
id	If dataset exists in NASA’s Earthdata or presumably from some other data provider like ESA, use that ID. If appropriate, add a suffix for any additional processing that has been performed, e.g. “OMSO2PCA_cog”. If dataset is not from NASA’s Earthdata, we can use a human readable name with underscores like “facebook_population_density”.
dashboard extension	To support the delta-ui we have added two new fields in a proposed dashboard extension. For now we are just adding the fields but after testing things out, we can formalize the extension with a hosted json schema. Dashboard extension properties are only required for collections that will be viewed in the delta-ui dashboard.
dashboard:is_periodic	True/False This boolean is used when summarizing the collection—if the collection is periodic, the temporal range of the items in the collection and the time density are all the front end needs to generate a time picker. If the items in the collection are not periodic, a complete list of the unique item datetimes is needed.
dashboard:time_density	year, month, day, hour, minute, or null. These time steps should be treated as enum when the extension is formalized. For collections with a single time snapshot this value is null.
item_assets	stac-extension/item_assets is used to explain the assets that are provided for each item in the collection. We’re not providing thumbnails yet, but this example below includes a thumbnail asset to illustrate how the extension will be used. The population of this property is not automated, the creator of the collection writes the item assets documentation. Item assets are only required for collections that will be viewed in the delta-ui dashboard.
summaries	The implementation of this core stac-spec field is use-case specific. Our implementation is intended to support the dashboard and will supply datetime and raster statistics for the default map layer asset across the entire collection. Currently summaries are manually updated with a delta-ui specific user defined function in pgstac.
title and description	Use these properties to provide specific information about the collection to API users and catalog browsers. These properties correspond to dataset name and info in the covid-api but the delta dashboard will use delta-config to set these values in the UI so the information in our stac collections will be for data curators and API users.
collection name style choices	Prefer lower-case kebab-case collection names. Decision: Should names align with underlying data identifiers or should it be an interpreted name? omi-trno2-dhrm and omi-trno2-dhrm-difference vs no2-monthly and no2-monthly-diff; bmhd-30m-monthly vs nightlights-hd-monthly
license	SPDX license id, license is likely available in CMR but we may need to research other sources of data. Default open license: CC0-1.0

item_assets example

"item_assets": {
    "thumbnail": {
      "type": "image/jpeg",
      "roles": [
        "thumbnail"
      ],
      "title": "Thumbnail",
      "description": "A medium sized thumbnail"
    },
    "cog_default": {
      "type": "image/tiff; application=geotiff; profile=cloud-optimized",
      "roles": [
        "data",
        "layer"
      ],
      "title": "Default COG Layer",
      "description": "Cloud optimized default layer to display on map"
    }
  }

summaries example for periodic collection

"summaries": {
    "datetime": ["2016-01-01T00:00:00Z", "2022-01-01T00:00:00Z"],
    "cog_default": {
      "max": 50064805976866820,
      "min": -6618294421291008
    }
  }

summaries example for non-periodic collection

"summaries": {
    "datetime": [
      "2020-01-01T00:00:00Z",
      "2020-02-01T00:00:00Z",
      "2020-03-01T00:00:00Z",
      "2020-04-01T00:00:00Z",
      "2020-05-01T00:00:00Z",
      "2020-06-01T00:00:00Z",
      "2020-07-01T00:00:00Z",
      "2020-08-01T00:00:00Z",
      "2020-09-01T00:00:00Z",
      "2020-10-01T00:00:00Z",
      "2020-11-01T00:00:00Z",
      "2020-12-01T00:00:00Z",
      "2021-01-01T00:00:00Z",
      "2021-02-01T00:00:00Z",
      "2021-03-01T00:00:00Z",
      "2021-04-01T00:00:00Z",
      "2021-05-01T00:00:00Z",
      "2021-06-01T00:00:00Z",
      "2021-07-01T00:00:00Z",
      "2021-08-01T00:00:00Z",
      "2021-09-01T00:00:00Z"
    ],
    "cog_default": {
      "max": 255,
      "min": 0
    }
  }