Instinctive Archer
Similar to radar, the rangefinder sends out a laser beam top aperture and looks for reflections from remote objects captured in the lower aperture, rangefinder then calculates the distance from the time between sending and reception of the reflection. For a much more detailed explanation click here

Laser should be low power to avoid danger of injury from the laser beam, so range is limited and certain topographies can be very challenging, for example try them on a roof for example, can be very misleading as they rangefinder gets so many different results back the answer depends on the way the rangefinder software is programmed
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