cochise, regarding the replacement read the previous post I couldn't have put any better. simply put, 90 meters outta cockpit window equates to 125 M RVR for all airbus models therefore whether you see 90 m or RVR 125 is reported is the same. Conclusion TDZ RVR replacement by pilot's observation is allowed regardless of NO report or reported below, above or whatever.
Relevant is what it is: closely connected or pertinent to the matter from the dictionary. In practical terms: if you skip the first 1/3 of the rwy and make intersection takeoff TDZ is irrelevant, isn't it? If you calculate the performance within 2/3 or the TODA, the last 1/3 is irrelevant, isn't it? If the rwy has got 4 RVR readings and over 4000 m long do you care bout the 4th RVR reading? No, hence irrelevant. Apropos it's valid for landing as well. Let's say a very long runway with only ILS CAT 1 approach from one end reports RVR of 100/100 M due to thick fog. You can clearly see the other half of the RWY from the flight deck due to local WX phenomena. Is RVR 100/100 relevant and if so for what? Well, it is for the ILS from one side but completely irrelevant from the other coz it's possible to shoot a visual.
