RFC 7946

RFC 7946

Overview

RFC 7946 is an Internet standards document that defines the GeoJSON format for encoding geographic data structures. It specifies how geographic features, feature collections, and geometry objects are represented in JSON for use across protocols and applications associated with Internet Engineering Task Force, World Wide Web Consortium, Open Geospatial Consortium, Mozilla Foundation, and Google. The specification impacts implementations by vendors such as Esri, Mapbox, Microsoft, Amazon (company), and Apple Inc. and informs projects like Leaflet (software), OpenLayers, PostGIS, QGIS, and GDAL.

History and development

The document emerged from discussions within the Internet Engineering Task Force and related working groups, drawing on precedents from earlier formats used by GeoRSS, KML (Keyhole Markup Language), GML (Geography Markup Language), and the Spatial Data on the Web Working Group. Influential contributors and organizations included participants from University of California, Berkeley, Massachusetts Institute of Technology, University of Oxford, Oracle Corporation, and NASA. The standardization process involved coordination with stakeholders such as OpenStreetMap, Natural Resources Canada, United States Geological Survey, and commercial vendors represented at forums like FOSDEM and OSGeo conferences.

Specification and structure

The specification defines top-level object types and their JSON structure, detailing required members and optional members used by implementers including Red Hat, IBM, Canonical (company), Atlassian, and Twitter. It prescribes how feature objects include properties for identifiers and attribute data, aligning with conventions familiar to databases like PostgreSQL and extensions such as PostGIS. The document’s structure influences APIs developed by platforms like CartoDB, MapQuest, HERE Technologies, and services provided by institutions like European Space Agency and National Oceanic and Atmospheric Administration.

Geometry types and properties

RFC 7946 enumerates geometry types including Point, MultiPoint, LineString, MultiLineString, Polygon, MultiPolygon, and GeometryCollection, guiding rendering in libraries such as D3.js, Three.js, Cesium (software), and Deck.gl. It explains property handling for feature attributes, identifiers, and bounding constructs used in datasets maintained by United Nations, World Bank, European Commission, and International Telecommunication Union. The treatment of polygons, linear rings, and winding order affects conversion from formats like Shapefile and interoperability with spatial databases like Oracle Spatial and Microsoft SQL Server.

Coordinate reference system and precision

The specification mandates usage of the WGS 84 datum expressed with longitude, latitude, and optional altitude, linking to standards maintained by International Organization for Standardization, National Institute of Standards and Technology, International Hydrographic Organization, and geodetic realizations such as WGS 84 (G1762). It addresses coordinate order and numerical precision considerations relevant to implementations at Esri, Trimble, Topcon, and research institutions like Scripps Institution of Oceanography and Jet Propulsion Laboratory. The document also discusses limitations and interoperability with projected coordinate systems used in projects by European Space Agency, USGS, and regional agencies like Ordnance Survey.

Media types and interoperability

RFC 7946 specifies media type registration, content negotiation, and interoperability expectations used by web servers and clients such as Apache HTTP Server, Nginx, Node.js, nginx Unit, and IIS (web server), and influences mapping services like Mapbox GL JS and Google Maps Platform. Interactions with web standards bodies like World Wide Web Consortium and registries managed by Internet Assigned Numbers Authority inform how user agents and middleware implement content types for exchange between applications including Jupyter, Grafana, and Kibana.

Implementations and adoption

Adoption spans open-source projects and commercial products: server-side processing in PostGIS, client rendering in Leaflet (software) and OpenLayers, mapping platforms by Mapbox and Esri, and data portals run by data.gov, europeandataportal.eu, Natural Resources Canada, and Australian Bureau of Statistics. Libraries in languages such as Python (programming language), JavaScript, Java (programming language), C++, and Go (programming language) implement the specification through projects like GDAL, Shapely (software), Turf.js, and geojsonio. The standard’s influence is evident in international initiatives involving United Nations, World Health Organization, and regional infrastructures like INSPIRE and Copernicus Programme.

Category:Internet standards