"Basemap does not match the layer's spatial reference (WKID: 25832) and was therefore dropped"

Error Message

The following error may be encountered when attempting to add a layer to a scene in ArcGIS Online:

"Basemap does not match the layer's spatial reference (wkid:25832) and was therefore dropped."

This issue occurs when the basemap used in a 3D scene has a different coordinate system than the data layer, in this case, UTM zone 32 (EPSG:25832). ArcGIS Online scenes require all layers and the basemap to share the same spatial reference.

Cause

The default basemaps in ArcGIS Online use Web Mercator (EPSG:3857), which is not compatible with layers in UTM32 (EPSG:25832) unless reprojected. If there's a mismatch, the platform will drop the incompatible layer from the scene.

Solution or Workaround

To work around this issue and keep the UTM32 data in its original projection, follow these steps in ArcGIS Pro:

1. Create a local Scene.
2. Remove the Ground Layer (unless you have one in UTM32).
3. Add a basemap that uses UTM32 (EPSG:25832) as its coordinate system, for example, a custom tiled layer designed for that projection.
4. Publish the scene as a Web Scene from ArcGIS Pro to ArcGIS Online.
5. In ArcGIS Online, open the newly published web scene and add the item you've saved that uses the same spatial reference.
6. The layer should now display correctly without triggering the spatial reference mismatch error: