[Patch] save coordinates in current map projection

[TobWen]

Since JOSM supports multiple map projections with the plugin "proj4j" and since it supports output in GeoJSON and GPX, it would be nice to export coordinates in the current map projection.

When working in EPSG:31466, coordinates get transformed back to EPSG:4326 on export. Since the transformation isn't perfect, errors are growing. Sure, that's not important for OSM, but JOSM can also be used outside of OSM.

GeoJSON, GPX and other formats support different map projects, so it would be nice to see an expert settings to switch from geographic coordinates to map coordinates.

[stoecker]

Regarding the errors it does not help, as JOSM always uses geographics coordinates. Different projections are only used for display. But the idea in itself may have other benefits.

[skyper]

Replying to stoecker:

Regarding the errors it does not help, as JOSM always uses geographics coordinates. Different projections are only used for display. But the idea in itself may have other benefits.

Like the problems with tool functions (e.g. create circle,align etc.) ?

[simon04]

attachment:10770.patch​ adds a *.proj.geojson exporter which writes the GeoJSON file with the currently set map projection. See ​http://geojson.org/geojson-spec.html#named-crs for the CRS specification in GeoJSON.

[simon04]

In 8813/josm:

fix #10770 - GeoJSON export: allow to save coordinates in current map projection

Adds a *.proj.geojson exporter which writes the GeoJSON file with the currently set map projection.

[Larry0ua]

Hi,

There is a problem with the CRS field, it does not comply with the geojson spec.
Spec says: A non-null CRS object has two mandatory members: "type" and "properties".
This CRS object should look like: {"type":"name", "properties":{"name":"EPSG:4326"}}

See ​http://geojson.org/geojson-spec.html#coordinate-reference-system-objects for examples.

[Larry0ua]

CRS name to the correct place in geojson

[simon04]

Replying to Larry0ua:

There is a problem with the CRS field, it does not comply with the geojson spec.

Please make sure to reopen tickets when there are sill problems. Otherwise – as in this case – further comments are overlooked. Fixed in #12803.

[simon04]

See also #13358: GeoJSON as in RFC 7946 no longer permits projections other than WGS84.