How do experienced riders develop their eye for distances?

Experienced riders develop their eye for distances through the accumulated pattern recognition of approaching thousands of fences at various paces on various horses over many years — a perceptual learning process that cannot be shortcut through any single exercise but that can be accelerated by specific training methods that develop the skill more efficiently than unguided jumping experience. The most efficient specific training method is systematic work with placing poles — a ground pole placed nine to ten feet before a fence that ensures a consistent takeoff regardless of what the rider sees or does, allowing the rider to feel the correct distance repeatedly without the variability of finding different distances. After many repetitions of feeling the correct placing-pole distance, the rider begins to recognize the canter quality and the visual appearance of the approach that produces this feel, establishing the internal reference point from which the eye develops. Working with an experienced trainer who calls the distance as it appears — calling long, short, or good as the rider approaches — develops the rider's ability to match their trainer's label to what they are seeing and feeling, building the vocabulary for what each distance category looks and feels like. Video review of jumping rounds allows the rider to see what they were actually riding versus what they felt they were riding, which is often illuminating early in the eye's development when the felt distance and the actual distance frequently diverge. Riding many different horses with different stride lengths and different jumping styles accelerates distance eye development by forcing the rider to calibrate to different stride lengths rather than becoming accustomed to a single horse's specific canter. The most important component of the process is that each jump is seen as a learning opportunity — actively asking after each fence what the distance was, what produced it, and what adjustment would have improved it rather than simply jumping and moving on without reflection.