Can't sleep either J_T?
Slope based Data - Generally only available (to my knowledge) within the Australian system. There's sure to be other countries supplying it, but I'm not aware of who they may be. It's all discrete obstacle data in the other countries within which I've done work.
Therein lies my generalisation that the TODA/STOD correction methods discussed here might not have much applicability outside the Australian system, even for a FAR 25 aircraft.
Regards,
Old Smokey