## Stereoscopic Distance Estimates

An observer can judge long distances between the observer and another object if the approximate size of the object or near by object is known.
The ratio of a typical persons arm length to the distance between their eyes is about 10. Using this information and trigonemetry the distance to the object
can be calculated. If the observer holds up their thumb and aligns it with the object with one eye closed and then notes the distance the object moves when
the eye used is switched. If it is known that a person is about 6 ft tall and the person appears to move 2x their height when the eyes are alternated, then that
person would be about 10 x (2 x 6 ft) away or 120 ft away.