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Developer invited to help advance SpatioTemporal Asset Catalog (STAC). But what is STAC? WHy does should it matter?

The Open Geospatial Consortium (OGC) and the SpatioTemporal Asset Catalog (STAC) community together invite developers to participate in the follow-up to the successful OGC API Hackathon. The ‘2019 OGC API – Features and Catalogues Sprint’ will occur at IQT CosmiQ Works, Arlington, VA, USA on 5-7 November, 2019.

OGC has been developing a new generation of web API standards leveraging OpenAPI to document requirements for implementation. In parallel, but in close coordination, the STAC community has been advancing a specification focused on imagery catalogs, which is based on OGC API – Features.

The Sprint is organized jointly with the STAC community to advance work on OGC’s emerging standards for Features and Catalogues, which is of mutual interest to both groups.

Developers will work on the Query and Filter ‘building blocks’ for data that will extend functionality of OGC API – Features and OGC API – Catalogue.

Read more here

But what is SpatioTemporal Asset Catalog (STAC)

To begin with, a “spatiotemporal asset” is any any file that represents information about the earth captured in a certain space and time. These could be anything like Imagery, SAR, Point Clouds, Data Cubes, Full Motion Video, etc. Thus, given the number of entities that generate and share such fiies its necessary that there exists a set of formats and schemas that data that is produces in.

The SpatioTemporal Asset Catalog (STAC) specification therefore provides a common language to describe a range of geospatial information, so it can more easily be indexed and discovered.

If you’re a consumer of any of the spatiotemporal datasets and your are building tools or platforms to automatically consume these data, you definitely will not be impressed at rolling your sleeves to write new code every time you want to use a new dataset.

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Also you can argue that the reason why exabytes of datasets that are available out there remain inaccessible because of the different formats that they are provided in.

This is where STC comes in.

“The STAC spec itself provides a lowest common denominator JSON format to wrap around any relevant data about the earth. The core GeoJSON object and related structures are designed for extension, so it can adapt to different domains. For more information about the specification, see the Spec Overview page. The core JSON pages can be transformed into browsable, interactive HTML pages with tools like STAC Browser. When STAC is used in concert with emerging formats like Cloud Optimized GeoTIFF the result vastly lowers the barriers for anybody to find and use geospatial assets like satellite imagery:” STAC Website.

STAC SPEC Schema
STAC SPEC Schema

According to their website,the STAC specification has 4 components that are independent however works best when together.

  • STAC Item is the core atomic unit, representing a single spatiotemporal asset as a GeoJSON feature plus datetime and links.
  • STAC Catalog is a simple, flexible JSON file of links that provides a structure for to organize and browse STAC Items. A series of best practices helps make recommendations for creating real world STAC Catalogs.
  • STAC Collection is an extension of the STAC Catalog with additional information such as the extents, license, keywords, providers, etc that describe STAC Items that fall within the Collection.
  • STAC API provides a RESTful endpoint that enables search of STAC Items, specified in OpenAPI, following OGC‘s WFS 3.
You can read more about this specification here

A number of tools have been developed by the community to help wiith using the spec as follow;

  • STAC Browser is a Vue-based browser for STAC catalogs.
  • Cognition is a pluggable, STAC-compliant, proxy for searching geospatial assets.
  • STAC Validator is a python utility to validate STAC json files against the STAC spec or against local STAC extensions.
  • Serverless STAC Crawler is a static STAC crawler that runs on Lambda and SQS integration.
  • Sat-utils is a set of utilities for searching/processing satellite data, including:
    • Sat-api is a STAC compliant web API for searching and serving metadata for geospatial data.
    • Sat-search is a Python 3 library and a command line tool for discovering and downloading publicly available satellite imagery.
    • Sat-stac is a Python 3 library for creating and working with STAC catalogs.
    • Sat-stats is a Python 3 library for calculating zonal statistics on images being stored remotely on S3.
    • Sat-fetch is a Python 2/3 library and command line tool for fetching, warping, and clipping remote imagery datasets.
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About OGC

The Open Geospatial Consortium (OGC) is an international consortium of more than 530 businesses, government agencies, research organizations, and universities driven to make geospatial (location) information and services FAIR – Findable, Accessible, Interoperable, and Reusable.
OGC’s member-driven consensus process creates royalty free, publicly available geospatial standards. Existing at the cutting edge, OGC actively analyzes and anticipates emerging tech trends, and runs an agile, collaborative Research and Development (R&D) lab that builds and tests innovative prototype solutions to members’ use cases.
OGC members together form a global forum of experts and communities that use location to connect people with technology and improve decision-making at all levels.

Visit www.opengeospatial.org for more info on theirwork.

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