"A rangefinder (also rangefinding telemeter, depending on the context), is a device used to measure distances to remote objects. Originally optical devices used in surveying, they ...
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soon found applications in other fields, such as photography and in the military. They were specially useful for finding the range of a target, such as in naval gunnery and anti-aircraft artillery. The word telemeter is derived from Ancient Greek τῆλε (têle) ´distant, far away´, and μέτρον (métron) ´something used to measure´." - (en.wikipedia.org 10.10.2022)