050052 : Unsupported spatial reference. TIN will be saved without projection information.

Description

TINs do not support all projections. This is one that isn't supported.

Solution

The TIN is still usable without a projection, so you don't have to do anything. If you must have a spatial reference associated with the surface, use a terrain dataset instead of a TIN. Terrain datasets support all projections in ArcGIS.