Why uses RA instead of DH in ILS CAT 2 approach ?

[Sepp]

Originally Posted by 42go

Roj - "At the point where you reach the DH, 97Ft RA, you will be 100Ft above the landing runway. (There is obviously a 3ft difference in the height of the ground at that point to the end of the runway, ARTE)

I hope that helps"

Not really - slightly irrelevant? It disregards the wording quoted by 66. I repeat, with emphasis:

A Category 2 decision height must be identified by reference to radio altitude and must not be less than
100ft arte or the OCH

What do you reckon the OCH is?

AIP Austria chart LOWW AD 2.24-6-4 states that the OCH for a Cat C a/c conducting a Cat II ILS rwy 29 at LOWW is 91ft. Does this allay your worries?