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TM 9-254
5-8.
Mil System.
a.
The artillery mil system is a means of angular measurement that lends itself to simple mental arithmetic. It
provides accuracy within the limits demanded by the military forces with distinct advantages of simplicity and convenience
not afforded by any other method of angular measurement. It is based on an arbitrary unit of measurement known as the
mil. The mil is exactly 1/6400 of a complete circle
b.
The mil is very nearly the angle between two lines which will enclose a distance of 1 meter at a range of 1,000
meters. Exact computation of the distance enclosed at 1,000 meters by 1 mil gives the result of 0.982 meters. Therefore
in assuming that 1 mil encloses 1 meter at 1,000 meters, an error of 0.018 meter or 1.8 cm is introduced. This error is
negligible for all practical purposes in the use of fire control instruments
c.
A circle of 1,000 meters radius would have a circumference of 6,283 meters. A 1 meter portion of the
circumference would be the 1/6283 fractional part of a circle. By choosing the mil as the 1/6400 fractional part of a circle,
sufficient accuracy is retained for all practical purposes while the number can be handled easily by mental arithmetic.
d.
The mil provides an extremely small unit of angular measurement that is easily adaptable to the small angles
encountered by the artillery man. For example, if an object has an angular width or height of 1 mil, it is 1 meter wide or
high at 1,000 meters; 2 meters wide or high at 2,000 meters; and so on. In angular height, a man is approximately 2 mils
tall at 1,000 meters or 1 mil tall at 2,000 meters
NOTE
The Navy mil and the French infantry mil are exactly 1 meter at a range of 1,000 meters. There are
6283.1853 Navy or French infantry mils in a complete circle.
e.
For quick approximate conversion from artillery mils to degrees, or vice versa, refer to figure 5-1. On this
chart locate the number of degrees or mils to be converted Directly across the black line of arc is its equivalent
f.
A more exact conversion from artillery mils to degrees, minutes, and seconds is listed in table 5-8.
Example:
Convert 2,569 mils to degrees
2,000
mils
=
112°
30'
0''
500
mils =
28°
7'
30"
60
mils =
3°
22'
30"
9
mils =
0
30'
22.5"
143
89'
82.5"
2,569
mils =
144°
30'
22.5"
5-17
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