For Category II operations the TDZ measurement is required, and for Category III operations the TDZ and MID measurements are mandatory. For CAT III without DH EU-OPS 1 requires only one RVR measuring point on the runway. FAA requires all 3 RVR readings to be available and above minimum. Approach ban Policy regarding an approach ban may differ from country to country. Usually the final approach segment may not be continued beyond the OM or equivalent DME distance if the reported RVR is below the published minima for the required transmissometers. After OM or equivalent position, if RVR becomes lower than the minima, the approach may be continued. FAA certified operators usually have OPS specs with FAF being nominated as approach ban point. Some countries set the approach ban at IAF.
