Milliradian

A milliradian is one-thousandth of a radian, approximately 0.0573 degrees. For small angles, it spans about one unit of distance per thousand units of range.

Mil-dot reticle: A telescopic sight pattern with spaced marks used to estimate range and adjust aim in milliradians. Its marks let shooters estimate target size or range using milliradian proportions.
Radian: An angular unit equal to the angle subtended at a circle’s center by an arc as long as its radius. A milliradian is defined as one-thousandth of this unit.
NATO mil: An angular unit defined as one six-thousand-four-hundredth of a full circle. Its value is close to, but not exactly, one milliradian.
Circle: A plane curve whose points are all equidistant from a fixed center. Radians are defined through arc length and radius on a circle.
Artillery: The use of large-caliber weapons to deliver munitions over long distances. Artillery systems use angular units, including milliradians, to measure direction and elevation.
Angle: A geometric measure of the rotation or separation between two intersecting lines or directions. Milliradians measure angles, using a scale convenient for small directional changes.
Soviet mil: An angular unit defined as one six-thousandth of a full circle. Its scale differs from the milliradian and from the NATO mil.
Central angle: An angle whose vertex lies at the center of a circle. The milliradian measures the central angle associated with a short circular arc.
Rangefinding: The measurement of distance to an object using optical, acoustic, or electromagnetic methods. Known object size and angular width in milliradians can yield an estimated range.
Arc length: The distance measured along a curved portion of a circle or other curve. At one milliradian, arc length equals one-thousandth of the circle’s radius.

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Minute and second of arcCompared with: It is an alternative small-angle unit used in optics, navigation, and engineering.