[gdal-dev] How to override WGS84 obligation with IETF GeoJSON?

[Even Rouault]

On mercredi 21 octobre 2020 14:03:37 CEST Rahkonen Jukka (MML) wrote:
> Hi,
> 
> We want to use GeoJSON with national coordinate systems like EPSG:3067,
> EPSG:3046 etc. We can write such GeoJSON with GDAL by using the default
> GeoJSON 2008 mode. However, in the RFC 7946 specification the rules about
> the winding order of polygons were clarified and some GeoJSON parsers
> complain about the polygons (in addition to coordinates).  So we would like
> to write polygons as in RFC 7946 and make the a prior arrangement as in the
> RFC 7946 text and use EPSG:3067 coordinates. I mean this text: "However,
> where all involved parties have a prior arrangement, alternative coordinate
> reference systems can be used without risk of data being misinterpreted."
> 
> At the moment the GeoJSON driver is missing the option for making this a
> prior arrangement because it interprets the standard strictly
> https://gdal.org/drivers/vector/geojson.html "Coordinates must be
> geographic over the WGS 84 ellipsoid, hence if the spatial reference system
> specified at layer creation time is not EPSG:4326, on-the-fly reprojection
> will be done by the driver."
> 
> I guess that there is no hidden switch to override this. What I would like
> to find is something like "-lco a_prior_arrangement=YES". But would it
> break anything if the GeoJSON 2008 part of the driver is modified to write
> the polygons also with counterclockwise external rings, clockwise internal
> rings?

Probably not, perhaps except a few unit tests.

-- 
Spatialys - Geospatial professional services
http://www.spatialys.com