Definition
The visual perception of depth and three-dimensional structure produced when the brain combines the slightly different images received from each of the two eyes. Because the eyes are separated horizontally, each one sees objects from a marginally different angle, and the brain fuses these two views into a single image that conveys distance and solidity.
Plain English
It is the way your two eyes work together to let you see the world in 3D. Each eye sees a slightly different picture, and your brain combines them so you can judge how near or far things are.
Context Anchor
Seen in aviation medical, vision, night flying, landing, taxi, and collision-avoidance discussions.
Derivation
From the Greek 'stereos', meaning 'solid', and 'opsis', meaning 'sight' or 'vision'. Literally, 'solid sight' — seeing the world as solid, three-dimensional shapes rather than as a flat picture.
Why Pilots Care
Accurate depth judgment helps pilots set the correct glide path, flare height, and spacing from other aircraft during visual approaches and landings.
Analogy
Similar to how two slightly offset camera views create the sense of depth in a 3D movie.
Grounding Statement
When you look at a nearby object with both eyes, your brain compares the two slightly different views and turns them into a sense of distance.
Intuition Check
Stereopsis is not the same as all depth perception. It is specifically the depth information your brain gets from using both eyes together.
Example Sentence 1
Because stereopsis only works at short distances, pilots judging the height of the runway during the flare also rely on cues like the apparent rate at which the ground expands in their view.
Example Sentence 2
Good stereopsis allowed her to maintain proper spacing behind the aircraft ahead on final approach.