How is the Observer-Target (OT) direction expressed?

The Observer-Target (OT) direction is expressed in mils to four digits because this method provides a precise angular measurement used in military operations. Mils are a unit of angular measurement that allow for more detailed and accurate targeting compared to degrees, particularly within the context of artillery and fire support. The use of four digits ensures that the measurement is specific enough to guide fire to the target accurately.

In military applications, the angular measurement in mils allows for effective coordination of strikes, as it directly correlates to the artillery's ability to adjust fire based on the position of the observer relative to the target. By using mils, which are defined as 1/6400 of a circle, fire support units can achieve the necessary precision, which is crucial in dynamic combat environments. This level of precision is particularly important when engaging moving targets or when the observer is at a significant distance from the target, where small errors can translate into large discrepancies in fire placement.

Other methods of expression, such as degrees or nautical miles, do not offer the same level of specificity required for effective direct fire control in military situations. This is why mils to four digits is the standard for expressing Observer-Target direction.