arcgis.geometry.union returns result without reference

ZiqingYu1 — Tue, 26 Aug 2025 09:12:18 GMT

Hi,

I need to union some Polygons into one using geometry.union, however, the result I got doesn't have a spatialReference, and I can't figure out why:

The Polygons are listed in a python list

And I tried both:

wkid = 32632 geo_union_2 = arcgis.geometry.union(shape_list, spatial_ref=wkid)

and

wkid = 32632 ref = arcgis.geometry.SpatialReference(wkid) geo_union_1 = arcgis.geometry.union(shape_list, spatial_ref=ref)

I got the warning

ArcPy\arcpy\geoprocessing\_base.py:502: RuntimeWarning: No spatial reference detected, defaulting to unknown coordinate system.
return self._gp.FromEsriJson(json)

And the result remains:

Anyone has an idea?

Re: arcgis.geometry.union returns result without reference

Clubdebambos — Thu, 28 Aug 2025 13:44:16 GMT

Hi @ZiqingYu1,

I ran into similar a couple of weeks ago. Strangely this only occurred for me in a standalone script. When I used in a Notebook in ArcGIS Online, this issue was not present. For outside, I just update the spatial reference for the geometry returned from union.

unioned = union(geom_list) ## union return a list, access with index[0] unioned[0]["spatialReference"] = {'wkid': 102100, "latestWkid" : 3857}

All the best,

Glen

topic arcgis.geometry.union returns result without reference in ArcGIS API for Python Questions

arcgis.geometry.union returns result without reference

Re: arcgis.geometry.union returns result without reference