STAC overview for Microsoft Planetary Computer Pro

This article provides an overview of the SpatioTemporal Asset Catalog (STAC) specification and how Microsoft Planetary Computer Pro uses it.

STAC specification

The STAC specification is an open, community-driven standard that makes it easy to find, combine, and use geospatial data. STAC provides a common structure for describing and cataloging "spatiotemporal assets." This structure lets you index and organize data across both space and time.

With STAC, organizations can make their geospatial assets accessible to a broad range of users. You can use STAC catalogs to organize many types of geospatial asset data, including:

• Satellite, aerial, and drone imagery
• LIDAR and SAR data
• Full Motion Video
• Hyperspectral data
• Other derived data formats

Additionally, you can use STAC with existing and emerging cloud-native data formats such as Cloud Optimized GeoTIFFs (COGs) and GeoParquet.

Since its release in 2018, many organizations quickly adopted STAC to organize their spatial data. These organizations include satellite operators, government agencies, civil society groups, and commercial companies.

The STAC specification consists of four complementary standards for describing geospatial assets, organizing those assets into groups, and making those assets searchable via common APIs. Specifically, these STAC standards include:

• STAC Catalog
• STAC Collection
• STAC Items
• STAC API

Planetary Computer Pro uses the STAC specification across all aspects of data management.

flowchart LR
    subgraph GC["GeoCatalog (Azure resource)"]
        direction TB
        subgraph C1["STAC Collection"]
            I1["STAC Items"]
        end
        subgraph C2["STAC Collection"]
            I2["STAC Items"]
        end
        subgraph C3["STAC Collection"]
            I3["STAC Items"]
        end
    end

    API["STAC API"]
    GC -- exposes --> API

    classDef resource fill:#0a3d62,stroke:#0a3d62,color:#ffffff;
    classDef collection fill:#e8f1fb,stroke:#0a3d62,color:#0a3d62;
    classDef items fill:#ffffff,stroke:#0a3d62,color:#0a3d62;
    classDef api fill:#1e824c,stroke:#1e824c,color:#ffffff;

    class GC resource;
    class C1,C2,C3 collection;
    class I1,I2,I3 items;
    class API api;

GeoCatalogs and STAC

Introduction to GeoCatalogs

The Planetary Computer Pro service enables you to create a GeoCatalog resource in your Azure subscription to ingest, manage, search, and distribute geospatial datasets. A GeoCatalog is an Azure resource that exposes a STAC-compliant API for the geospatial data you manage with it. In addition to STAC API support, a GeoCatalog provides ingestion, managed storage, identity-based access control, visualization, and other Azure-native capabilities that aren't part of the STAC specification itself.

From a STAC API perspective, a GeoCatalog presents a top-level STAC Catalog object that groups its STAC collections and STAC Items. You can view that top-level STAC Catalog JSON for a specific GeoCatalog by using the JSON web viewer at https://<your geocatalog uri>/json-api?path=/. For more information about the STAC Catalog specification, see STAC Catalog Spec.

A GeoCatalog is defined using the following information:

Currently, Planetary Computer Pro can deploy GeoCatalogs in the following Azure regions:

• East US
• North Central US
• West Europe
• Canada Central
• UK South
• US Government Virginia

You can deploy a GeoCatalog by using the Azure portal or the Azure REST API. To learn how to deploy a GeoCatalog into your Azure subscription, see create a GeoCatalog resource.

STAC collections

Introduction to collections

A GeoCatalog allows you to create collections to store and organize geospatial datasets on Azure. Use a STAC collection to describe a group of STAC Items that share properties and metadata, such as a common geographic area or sensor. For more information about the STAC collection concept, see STAC collection Spec.

Collection definition

Planetary Computer Pro adheres to the STAC collection specification, which defines a set of common fields to describe the dataset and included Items.

Within a collection, you can specify the type and structure of data stored in that collection. You can also add render configuration settings to visualize data within the collection using Planetary Computer Pro's Explorer.

You define collections in GeoCatalog in JSON format. The definition includes the following fields:

Item assets

The item_assets field at the collection level shows what assets (data files) are available in any child Item. The listed assets in this field don't imply that all assets are available for all Items. The field shows the union of the available assets, not the intersection. You enable this field in a GeoCatalog through the item_assets extension of the STAC specification. You need the items assets extension if you want to visualize Items in the GeoCatalog Explorer.

The item_assets field is an object with at least two of the following fields:

Collection JSON examples

The following example shows a minimal collection JSON. For more fields, see the STAC collection specification.

{
  "id": "example-collection",
  "type": "Collection",
  "title": "Example collection",
  "description": "An example collection",
  "license": "CC-BY-4.0",
  "extent": {
    "spatial": {
      "bbox": [
        [
          -180,
          -90,
          180,
          90
        ]
      ]
    },
    "temporal": {
      "interval": [
        [
          "2018-01-01T00:00:00Z",
          "2018-12-31T23:59:59Z"
        ]
      ]
    }
  },
  "links": [],
  "stac_version": "1.0.0"
}

For a slightly more complex example JSON, see this example describing an open dataset from the National Agriculture Imagery Program (NAIP).

Collection configuration

To visualize collections in the GeoCatalog Explorer, you must define several configurations, including:

• Mosaic definition
• Render configuration
• Tile settings
• Queryable fields

STAC items

Introduction to STAC items

A GeoCatalog stores and organizes geospatial datasets into collections. A STAC Item is the core object in a GeoCatalog's collection. It contains metadata for a scene and links to assets from that scene, such as a satellite image. An Item's metadata allows GeoCatalog to search and query spatial assets. For more information about STAC Items, see STAC Item Spec.

Item definition

The Planetary Computer Pro adheres to the STAC Item Specification, which defines a set of common fields to describe an Item, such as time range and the assets related to the Item. You define Items in JSON format and can flexibly expand them to include more metadata.

A valid STAC Item requires the following fields:

Common metadata for Items beyond these required fields includes date and time, licenses, providers, instrument, and more.

Item JSON example

The following example shows a basic item JSON.

{
  "stac_version": "1.0.0",
  "stac_extensions": [],
  "type": "Feature",
  "id": "20201211_223832_CS2",
  "bbox": [
    172.91173669923782,
    1.3438851951615003,
    172.95469614953714,
    1.3690476620161975
  ],
  "geometry": {
    "type": "Polygon",
    "coordinates": [
      [
        [
          172.91173669923782,
          1.3438851951615003
        ],
        [
          172.95469614953714,
          1.3438851951615003
        ],
        [
          172.95469614953714,
          1.3690476620161975
        ],
        [
          172.91173669923782,
          1.3690476620161975
        ],
        [
          172.91173669923782,
          1.3438851951615003
        ]
      ]
    ]
  },
  "properties": {
    "datetime": "2020-12-11T22:38:32.125000Z"
  },
  "collection": "simple-collection",
  "links": [
    {
      "rel": "collection",
      "href": "./collection.json",
      "type": "application/json",
      "title": "Simple example collection"
    },
    {
      "rel": "root",
      "href": "./collection.json",
      "type": "application/json",
      "title": "Simple example collection"
    },
    {
      "rel": "parent",
      "href": "./collection.json",
      "type": "application/json",
      "title": "Simple example collection"
    }
  ],
  "assets": {
    "visual": {
      "href": "[URL]",
      "type": "image/tiff; application=geotiff; profile=cloud-optimized",
      "title": "3-Band Visual",
      "roles": [
        "visual"
      ]
    },
    "thumbnail": {
      "href": "[URL]",
      "title": "Thumbnail",
      "type": "image/jpeg",
      "roles": [
        "thumbnail"
      ]
    }
  }
}

STAC extensions

Currently, a GeoCatalog automatically adds the following extensions to all ingested collections:

• item-assets
• table

You can also use STAC extensions at the STAC Item level.

For a full list of STAC extensions, including the maturity of each one, see the STAC extensions page on GitHub.

STAC API

The Planetary Computer Pro's APIs conform to the STAC API specification, so you can quickly and easily search petabyte-scale datasets to find specific data assets that meet your needs. Once you identify these assets, you can view or download the assets by using GeoCatalog's APIs.

Next steps

Related content

• Create a STAC Collection with the Microsoft Planetary Computer Pro web interface
• Create a STAC Item in Microsoft Planetary Computer Pro