aggregation.md

Aggregation

Stac-fatsapi-elasticsearch-opensearch supports the STAC API Aggregation Extension. This enables aggregation of points and geometries, as well as frequency distribution aggregation of any other property including dates. Aggregations can be defined at the root Catalog level (/aggregations) and at the Collection level (/<collection_id>/aggregations). The Filter Extension is also fully supported, enabling aggregated returns of search queries. Any query made with /search may also be executed with /aggregate, provided that the relevant aggregation fields are available,

A field named aggregations should be added to the Collection object for the collection for which the aggregations are available, for example:

Available aggregations are:

• total_count (count of total items)
• collection_frequency (Item collection field)
• platform_frequency (Item.Properties.platform)
• cloud_cover_frequency (Item.Properties.eo:cloud_cover)
• datetime_frequency (Item.Properties.datetime, monthly interval)
• datetime_min (earliest Item.Properties.datetime)
• datetime_max (latest Item.Properties.datetime)
• sun_elevation_frequency (Item.Properties.view:sun_elevation)
• sun_azimuth_frequency (Item.Properties.view:sun_azimuth)
• off_nadir_frequency (Item.Properties.view:off_nadir)
• grid_code_frequency (Item.Properties.grid:code)
• centroid_geohash_grid_frequency (geohash grid on Item.Properties.proj:centroid)
• centroid_geohex_grid_frequency (geohex grid on Item.Properties.proj:centroid)
• centroid_geotile_grid_frequency (geotile on Item.Properties.proj:centroid)
• geometry_geohash_grid_frequency (geohash grid on Item.geometry)
• geometry_geotile_grid_frequency (geotile grid on Item.geometry)

Support for additional fields and new aggregations can be added in the OpenSearch database_logic.py and ElasticSearch database_logic.py files.

"aggregations": [
    {
      "name": "total_count",
      "data_type": "integer"
    },
    {
      "name": "datetime_max",
      "data_type": "datetime"
    },
    {
      "name": "datetime_min",
      "data_type": "datetime"
    },
    {
      "name": "datetime_frequency",
      "data_type": "frequency_distribution",
      "frequency_distribution_data_type": "datetime"
    },
    {
      "name": "sun_elevation_frequency",
      "data_type": "frequency_distribution",
      "frequency_distribution_data_type": "numeric"
    },
    {
      "name": "platform_frequency", 
      "data_type": "frequency_distribution",
      "frequency_distribution_data_type": "string"
    },
    {
      "name": "sun_azimuth_frequency",
      "data_type": "frequency_distribution",
      "frequency_distribution_data_type": "numeric"
    },
    {
      "name": "off_nadir_frequency",
      "data_type": "frequency_distribution",
      "frequency_distribution_data_type": "numeric"
    },
    {
      "name": "cloud_cover_frequency",
      "data_type": "frequency_distribution",
      "frequency_distribution_data_type": "numeric"
    },
    {
      "name": "grid_code_frequency",
      "data_type": "frequency_distribution",
      "frequency_distribution_data_type": "string"
    },
    {
      "name": "centroid_geohash_grid_frequency",
      "data_type": "frequency_distribution",
      "frequency_distribution_data_type": "string"
    },
    {
        "name": "centroid_geohex_grid_frequency",
        "data_type": "frequency_distribution",
        "frequency_distribution_data_type": "string"
    },
    {
        "name": "centroid_geotile_grid_frequency",
        "data_type": "frequency_distribution",
        "frequency_distribution_data_type": "string"
    },
    {
      "name": "geometry_geohash_grid_frequency",
      "data_type": "frequency_distribution",
      "frequency_distribution_data_type": "numeric"
    },
    {
      "name": "geometry_geotile_grid_frequency",
      "data_type": "frequency_distribution",
      "frequency_distribution_data_type": "string"
    }
]