2021.09.28 13:49 "[Tiff] Proposal to create a OGC BigTIFF standard", by Even Rouault

2021.09.30 11:38 "Re: [Tiff] Proposal to create a OGC BigTIFF standard", by Kemp Watson

For completeness here, there is an SGI tag for 3D data registered in TIFF:

(32997) IMAGE_DEPTH Type LONG Count 1 Value 1

Whether anyone uses it, I have no idea.

Kemp