You may find yourself from time to time needing to get a somewhat accurate range estimation without the use of a laser rangefinder or other precision equipment. Most modern optics have various methods to help estimate the range of a variety of objects.
Mil-Dot or Mil-Reticle Pattern
The most common in western optics, the mil-dot pattern uses the angular measurement of milliradians (or mils).
Binoculars / Vector 21
The standard set of binoculars, as well as the Vector 21 use a mil pattern, labeled every 10 mils.
Leupold Mk. 4 / M8451 SDSS / MOS* / LRPS* / ACE SPOTTING SCOPE
These scopes feature a mil-dot pattern, but are incremented every 1 mil (with .5 mil marks as well) due to their higher magnifying power.
*These two are BI scopes (ACE 2D Versions) Their patterns are accurate ONLY at the highest level of zoom. (RHS reticles scale correctly with level of zoom)
Combat Rifle Scopes
Trijicon ACOG (RCO), Elcan LDS
Both the ACOG series (RHS) and Elcan (3CB) feature a small horizontal mil-reticle pattern (unlabeled, without numbers) incremented in 5 mils with larger 10 mil marks (same as the binoculars)
Estimating Range Using Mils
Now that we know how to read the various mil patterns on scopes, we can actually make a range estimation. The formula is quite simple when estimating range in meters. We need two inputs, an actual length, width, or height of the target we are trying to get the range of. We also need to measure that same length in mils using our reticle pattern. Lets use one of the more common measurements, the height of a man. The average height of an ArmA character is 1.8 meters (keep in mind thing like headgear or stance may change the characters height).
Range (meters) = [Length of Target (meters) / Length of target (measured in mils)] x 1000
the range of the target in meters is equal to the actual length of the target in meters divided by the observed length of the target measured in mils, multiplied by one thousand.
Lets see this in action. Say we have a man at an unknown distance from us. We observe the target and measure in mils his height at about 4 mils. Given our average height of the character is 1.8m, we can complete our equation.
1.8 (Average height of character) / 4.0 (measured height in mils) x 1000
ESTIMATED RANGE = 450 METERS
Using a rangefinder, we can see our estimate was only 12m off from the actual range of the target, more than close enough to land a hit with a sniper rifle, or give an accurate range for a polar fire mission. As stated before, the length or width of an object can be used as well, so knowing the approximate length of vehicles for example can help you to make more accurate shots with your anti-tank weapons. Obviously the further away the target is, the more difficult this method becomes, as your measurement will be less precise. Ill add to this post some more methods as I get time.
ACOG, Elcan, etc.
In this example the target is estimated at 400m
PSO-1, various Soviet/Russian Optics
In this example the target is estimated at 350m
Edited by ThePieSpy, 2016-08-18 @ 15:25.