range finder

A device used to determine the distance between a 'target' and the observer. Range finders are usually seen in military applications, though they are also utilized in civilian use cases such as Golf, Photography. or forestry.

there are three predominant categories of range finder:
- Laser
Usually the most compact, Laser Range Finders are often seen next to snipers, used to adjust lead for a shot.
- Stereoscopic
A horizontal tube with apertures at either end and a pair of eye pieces near the center. Stereoscopic Range Finders make use of human stereoscopic vision to line up the images coming from either end to find an accurate distance to target.
- Coincidence
Similar to the Stereoscopic Range Finder, albeit with only one eye piece, Coincidence Range Finders split the incoming images and overlay one top above the other's bottom. when the two images are adjusted to line up, an accurate range will be found.

In general, Stereoscopic and Coincidence Range Finders benefit from being wider and higher up, leading to them predominantly being seen high in the superstructure of warships up through WWII before being phased out in favor of radar range finders. Medium-to-large naval turrets often featured one or more integrated range finders, such as are seen protruding from the sides of the 16-inch/50-caliber mark 7 gun turrets of the Iowa-class.