= 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: [https://tools.ietf.org/html/rfc7946 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.

== Related ticket ==

#6705 

== Implementation ==

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

== Voting history

+1 from JukkaR, HowardB, DanielM and EvenR