Which devices measure Runway Visual Range (RVR) along the runway?

• A. Transmissometers or forward-scatter meters along the runway.
• B. Barometers.
• C. Anemometers.
• D. Thermometers.

Answer: (A)

RVR is the visual range along the runway path used by pilots during landing and takeoff, so you need sensors that measure how far you can see along that specific line. Transmissometers project a beam of light across a defined path to a receiver, and the amount of light that reaches the receiver is reduced by fog, haze, or other particles. That attenuation is converted into an RVR value for that path. Forward-scatter meters work on a similar idea but detect light scattered by particles along the line of sight and translate that into a visibility reading for the runway segment. These devices are installed along the runway (often at touchdown, midpoint, and rollout) to provide accurate, segment-based RVR readings. Barometers, anemometers, and thermometers measure other weather parameters—air pressure, wind speed, and temperature, respectively—and do not provide the direct runway-path visibility used for RVR.