For info, from our Ops Manual (UK, (CAA-approved!) long haul operator)-
1)For Cat II/III Ops with no decision height (ie DH = 0'), "at least one RVR value must be available at the aerodrome".
2)Under "Failed and Downgraded equipment" - "Touchdown Zone RVR may be temporarily replaced by Mid zone RVR if approved by the State of the Aerodrome. RVR may be reported by human observations."
3) Stop end RVR is always advisory (ie not required).
So, multiple RVRs are not required - we only need Touchdown RVR to do a Cat IIIB, and it can be replaced by Mid point RVR. And a human observation is perfectly acceptable - but as said above, the chances of finding a major aiport with a human observer available are probably a bit slim.
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