django/django · error · GEOSException

Calling transform() with no SRID set is not supported.

Error message

Calling transform() with no SRID set is not supported.

What it means

Raised by GEOSGeometry.transform (geometry.py:496-520) as a GEOSException when the geometry has no SRID (srid is None) or a negative SRID and the caller passed a target SRID/transform that is not already a gdal.CoordTransform. Reprojection requires a known source SRS, so Django refuses to guess.

Source

Thrown at django/contrib/gis/geos/geometry.py:518

        PROJ string. By default, transform the geometry in-place and return
        nothing. However if the `clone` keyword is set, don't modify the
        geometry and return a transformed clone instead.
        """
        srid = self.srid

        if ct == srid:
            # short-circuit where source & dest SRIDs match
            if clone:
                return self.clone()
            else:
                return

        if isinstance(ct, gdal.CoordTransform):
            # We don't care about SRID because CoordTransform presupposes
            # source SRS.
            srid = None
        elif srid is None or srid < 0:
            raise GEOSException(
                "Calling transform() with no SRID set is not supported."
            )

        # Creating an OGR Geometry, which is then transformed.
        g = gdal.OGRGeometry(self._ogr_ptr(), srid)
        g.transform(ct)
        # Getting a new GEOS pointer
        ptr = g._geos_ptr()
        if clone:
            # User wants a cloned transformed geometry returned.
            return GEOSGeometry(ptr, srid=g.srid)
        if ptr:
            # Reassigning pointer, and performing post-initialization setup
            # again due to the reassignment.
            capi.destroy_geom(self.ptr)
            self.ptr = ptr
            self._post_init()
            self.srid = g.srid

View on GitHub (pinned to ae25a40be0)

Solutions

Set an explicit SRID before transforming: geom.srid = 4326; geom.transform(3857).
Construct the geometry with the SRID up front: GEOSGeometry('POINT(0 0)', srid=4326).
If only the target SRS is known, build a gdal.CoordTransform(source_srs, dest_srs) and pass that instead of a bare SRID.

Example fix

// before
geom.transform(3857)  # geom.srid is None
// after
geom.srid = 4326
geom.transform(3857)

Defensive patterns

Strategy: validation

Validate before calling

def safe_transform(geom, target):
    if geom.srid is None or geom.srid < 0:
        geom.srid = 4326  # or raise, depending on policy
    return geom.transform(target)

Type guard

def geometry_has_srid(geom):
    return geom.srid is not None and geom.srid >= 0

Try / catch

from django.contrib.gis.geos.error import GEOSException
try:
    geom.transform(3857)
except GEOSException:
    geom.srid = 4326  # assume WGS84
    geom.transform(3857)

Prevention

Always set an SRID when constructing geometries from WKT.
Validate geom.srid is set before any transform pipeline.
Prefer CoordTransform when source SRS varies per record.

When it happens

Trigger: Calling geom.transform(3857) (or any int/WKT/PROJ-string target) on a geometry whose geom.srid is None or < 0 and where the target is not a CoordTransform (a CoordTransform bundles its own source SRS and bypasses this check).

Common situations: Loading geometries from WKT without specifying an SRID, geometries deserialized from formats that drop SRID, or input pipelines that forget to call geom.srid = 4326. Also from negative SRIDs used as 'unknown' sentinels.

Related errors

AI-assisted analysis of django/django@ae25a40be0 (2026-08-06). Data as JSON: /api/errors/f8980eea64aeef45. Report an issue: GitHub.