Sorry, points of the compass don't come into it as Met Viz is the lowest value in any direction as estimated from the point of the observer.
Each station made up their own "spotting" card with known distances to significant landmarks such as line of trees, church spires, radio masts etc. There was a bit of guesswork when you could see one point at 1200m reasonably well but not the next at 1500m so the observer would say 1400m as an educated guess.
Wasn't RVR just a case of counting the lights ?
Happy Landings
