RFC 65: RFC 7946 GeoJSON

Authors: Sean Gillies

Contact: sean at mapbox.com

Status: Adopted, implemented

Implementation version: 2.2

Summary

GeoJSON has been standardized by the IETF: RFC 7946. Updates to the OGR GeoJSON driver are needed so that it may write RFC 7946 GeoJSON.

Rationale

The RFC 7946 standard is backwards compatible with the legacy definition of GeoJSON, but has a few differences (see https://tools.ietf.org/html/rfc7946#appendix-B). For OGR, the most significant are: removal of "crs" (CRS84 only), counter-clockwise winding of polygons, geometry splitting at the antimeridian, and representation of bounding boxes at the antimeridian and poles. Note: RFC 7946 explicitly restricts to 2D and 3D coordinates, and forbid use of the M dimension for example. This was already the case in the existing driver for the GeoJSON 2008 output.

Consensus on the gdal-dev list is that developers should be able to require RFC 7946 GeoJSON by configuring layer creation with an option and that it be an all-or-nothing switch.

Changes

A layer creation option will be added for the GeoJSON driver, e.g., RFC7946=TRUE. When "on", OGR will write GeoJSON with CRS84 coordinates (reprojecting as needed) with 7 places of precision by default, polygons wound properly, and geometries split at the antimeridian.

Related to that work, the OGRGeometryFactory::transformWithOptions() method has been improved to better deal with reprojection of geometries from polar projections, and projections that span the antimeridian, to EPSG:4326

Updated drivers

GeoJSON

SWIG bindings (Python / Java / C# / Perl) changes

None

Utilities

Utilities will implement RFC 7946 by using the layer creation option.

Documentation

Documentation of the new layer creation option will reference RFC 7946.

Test Suite

The ogr_geojson.py file tests the effect of the new option.

Compatibility Issues

As this is a opt-in parameter, no backward compatibility issue. GeoJSON files conformant to RFC 7646 can be read by previous GDAL/OGR versions.

Implementation

Implementation has been done by Even Rouault and sponsored by Mapbox.

Voting history

+1 from JukkaR, HowardB, DanielM and EvenR