I used to be a gunner on an M1A1, and although we had laser range finders, we also practiced with the old style optical sights that were installed alongside the main gun.  How range finding works with optical sites is you usually have a series of marks in the viewfinder that you use to physically measure what you&#x27;re aiming at, so if the tank&#x2F;plane&#x2F;whatever is between particular two pips (or whatever; edit iirc the M1 had two curved lines you would placer over the target) you know that it&#x27;s about x meters away. The pips are calculated knowing the average length of the object, so this is, in practice, close enough.<p>The procedure is; measure the target, then use cross marks on the cross hairs to raise the gun tube to the appropriate level, manually guess lead and defilade, fire, on the way. It obviously takes practice to get good at.  I found it curious that the US Army continued to teach&#x2F;train&#x2F;use this method, as well as land navigation with compass&#x2F;mapp instead of gps. The idea is to not rely on technology entirely.<p>Edit: turns out I am describing stadiametric rangefinding:<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Stadiametric_rangefinding" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Stadiametric_rangefinding</a>