GEOSGeometry fails on instance with GEOJson and srid not 4326.

[Walter Lorenzetti]

On creating a GEOSGeometry intance by a GEOJson string with a srid not 4326, I obtain this error:
coord = '{"type": "Point", "coordinates": [10000, 10000]}'

g = GEOSGeometry(coord, srid=3857)
Traceback (most recent call last):
  File "<input>", line 1, in <module>
  File "/home/envs/g3w_suite_dj22/lib/python3.6/site-packages/django/contrib/gis/geos/geometry.py", line 732, in __init__
    raise ValueError('Input geometry already has SRID: %d.' % input_srid)
ValueError: Input geometry already has SRID: 4326.

So to fix it I use this not beautyfull solution:

g = GEOSGeometry(GEOSGeometry(coord).wkt, srid=3857)

Thanks in advance.
W

[Mariusz Felisiak]

It's ​documented that "for the GeoJSON format, the SRID is set based on the crs member. If crs isn’t provided, the SRID defaults to 4326". So if you want to use GeoJSON with a different SRID you need to use crs, e.g.

{
  "type": "Point",
  "coordinates": [2, 49],
  "crs": {
    "type": "name",
    "properties": {
      "name": "urn:ogc:def:crs:EPSG::3857"
    }
  }
}

[MangoMango666]

I would argue in favor of this bug that when a GeoJSON is created from PostGIS using the ST_AsGeoJSON function, there is 'crs' member (only 'type' and 'coordinates').

Also, in the same page of the doc, it is written "All these constructors take the keyword argument srid.", hence the confusion of Walter.