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Range Estimation was last updated: 20091228 1801

Range Estimation
Range estimation is the process of determining the distance between
two points. The ability to accurately determine range is the key
skill needed by the shooter to make a shot of an unknown distance.

Range can be determined by measuring or by estimating. Below are
three main factors that affect the appearance of objects when determining
range by eye.

Nature of the Target -
Objects of regular outline, such as a house, will appear closer than
one of irregular outline, such as a clump of trees. A target that contrasts with
its background will appear to be closer than it actually is. A partially exposed
target will appear more distant than it actually is.

Nature of the Terrain -
Observing over smooth terrain, such as sand, water, or snow, causes
the observer to underestimate distance targets. Objects will appear nearer
than they really are when the viewer is looking across a depression, most of
which is hidden from view. They will also appear nearer when the viewer is
looking downward from high ground or when the viewer is looking down on a
straight, open road or along railroad tracks.

As the observer's eye follows the contour of the terrain, he tends to
overestimate the distance to targets. Objects will appear more distant than they
really are when the viewer is looking across a depression, all of which is visible.
They also appear more distant than they really are when the viewer is looking
from low ground toward high ground and when the field of vision is narrowly
confined, such as in twisted streets or on forest trails.

Light Conditions -
The more clearly a target can be seen, the closer it will appear. A
target viewed in full sunlight appears to be closer than the same target
viewed at dusk or dawn or through smoke, fog, or rain. The position of the
sun in relation to the target also affects the apparent range. When the sun is
behind the viewer, the target appears closer. When the sun appears behind
the target, the target is more difficult to see and appears farther away.

MILING THE TARGET FOR RANGE -
When ranging on a "human sized" target, the shooter may use two different
methods. The first method is to range on the target using the vertical
crosshairs and mil dots. The second method is to use the horizontal crosshairs
and mil dots.

Vertical Method -
A sniper most often uses this method of range finding when using
the M3A. He must become very good at estimating the height of the target in
either meters or feet and inches. The shooter has the option of using a 1-meter
(head to crotch) target frame or using the entire target (head to toe) as the
target frame. To use the vertical method, the shooter places the crosshairs at
either the feet or crotch, and measures to the top of the head of the target.
The mil value is then read for that target. The shooter must determine the
height of the target if he is not using the 1-meter target frame. Since the
telescope is graduated in meters, the height of the target must be converted
into meters. The shooter then calculates the range using the mil-relation
formula. The estimation of the height of the target may be the most
important factor in this formula. An error of 3 inches on a 5-foot 9-inch target
that is actually 5 feet 6 inches results in a 19-meter error at a reading of
4 mils.

Normal height of the human = 69 inches

69 inches * 25.4 / Size of target in mils (4) = Range to target in meters (438.5 or 440meters)

NOTE: This example may prove to be of specific use when facing an enemy
entrenched in bunkers or in dense vegetation.

Horizontal Method -
The horizontal method is based upon a target width of 19 inches at
the shoulders. This technique can be very accurate out to ranges of 350
meters, and is very effective in an urban environment. Beyond this range it is
no longer effective. The shooter should use this method to double-check ranges
derived from groin to head. For example, a range estimate derived from a
groin to head (1 meter) measurement of 2 mils would be equal to a
1 mil shoulder to shoulder measurement (horizontal = 1/2 vertical). A good
rule of thumb is that if the target is smaller than 1 1/2 mils (322 meters),
it is more accurate to use the vertical method in combination with the
horizontal method.

The mil dots in an M3A are 3/4 MOA in diameter. Therefore, it is
important to note where on the dots the bottom or the top of the target falls
within the mil dot. The mil dots are spaced 1 mil from center to center,
or cross to center of first dot.

Objects viewed from an oblique angle may cause the shooter to
overestimate the range to that object. Shooters should be aware of this effect
and compensate accordingly.