A transmissometer is a ground-based optical instrument used at airports to measure Runway Visual Range (RVR) by determining how much light is lost over a known distance near the runway. It shines a calibrated light beam across a fixed path to a receiver and measures how much of that light is “transmitted” through the air.
Key characteristics:
- Measurement principle: Sends a light beam from a projector to a receiver at a known distance. The system measures how much the light is attenuated by fog, rain, snow, or haze.
- Output: Converts light loss into a visibility value expressed as RVR (e.g., 300 m, 600 m).
- Placement: Typically installed near the touchdown, midpoint, and rollout areas of the runway to provide local RVR readings for each zone.
- Operational role: Feeds real-time RVR data to ATC and airport systems so they can determine whether approaches and landings are allowed for CAT I, II, or III operations.
Application in DCS World
DCS simulates low visibility conditions (fog, reduced visibility, low cloud bases), which effectively mimic what a transmissometer would be measuring in the real world.
DCS does not model transmissometers or RVR sensors explicitly — there is no ground equipment, no RVR readout, and ATC does not report RVR values. Mission designers just set visibility numerically in the weather panel.
Cadets should treat transmissometers as real-world background knowledge that explains where RVR numbers come from. In DCS, they can approximate transmissometer-driven conditions by adjusting fog and visibility distance, then practicing CAT I–III-style approaches in progressively worse settings.