How are scope rings height measured relative to mounting rail?

[LostInTranslation]

On rail there are (listed from top to bottom, all accessible from top) top of rail - highest surface, widest point of side rib, and lowest surface. When height for scope rings/mounts is specified -is there a standard to which of those three points it is to (from centerline of scope)?

Intuitively it makes sense to use widest point of the rib as that's where scope mount is aligning to...

 

[Rob01]

Top. Highest part where the ring sets.

 

[PinesAndProjectiles]

 

[_Windrider_]

Ring height calc



(Obj diameter/2)-((obj diameter-tube diameter)/2)+lens cap thickness + cant



(56/2) + ((56-34)/2)+3

Example:

28+11+3= 42 mm or 1.6”