What formula is used to compute the angular deviation between the OT line and the known point?

The mil relation formula is employed to compute the angular deviation between the Observation Target (OT) line and a known point because it is specifically designed to convert distance measurements into angular measures, expressed in mils. This is critical in fire support operations, where precise targeting is needed to align artillery or other support fire effectively. The mil relation formula utilizes the relationship between angles and distances, which is vital when determining the necessary adjustments for angles of fire based on geographic or battlefield conditions. In contrast, other formulas such as the distance equation, altitude adjustment formula, and grid coordinate method serve different purposes and do not provide the specific angular deviation needed in this context.