It seems impossible to redefien the given projection of a TIN. I just want to redefine the projection system for multiple TINs. Although it's already possible to define it through ArcCatalogue for each TIN, it is not possible to reproject the TIN. It would be handy to have a particular function or toolbox allowing to reproject the Tin in a chosen projection system, instead of reprojecting the datasets andrecreating a new set of TIN.
