A bearing describes the horizontal direction from an origin to a target or reference point. Expressed as an angle, it requires a named reference direction and an angular unit. During military isolation, it can describe the direction to a landmark or report a person's location relative to a prepared reference point. What matters is which point the direction starts from and which other point it leads towards.
Origin and target
“From my present halt to the single water tower: ninety degrees true” describes a direction from the person to the tower. “From the water tower to my halt” describes the relationship in the opposite direction. A receiver who reads the first statement as placing the person east of the tower, although the person took a bearing to a tower lying to the east, places them on the wrong side of the reference point.
A place name is also insufficient if several towers, junctions or terrain features could be meant. The origin and target must identify the same places for both parties. A precise angle to a misidentified tower still produces an incorrect spatial relationship. In US land navigation, a direction angle measured from a north reference is also called an azimuth; here, the term denotes the angular direction rather than an additional position value.
Which north is the reference?
True north is the direction along the local meridian towards the geographic North Pole. Magnetic north is the direction of the horizontal component of Earth's local magnetic field, with which an undisturbed magnetic compass aligns. Grid north is the north direction of the map grid in use. It can be rotated relative to true north because a flat coordinate grid represents the curved surface of the Earth.
Magnetic declination, also called variation, is the angular difference between true and magnetic north. It changes with location and time. The difference between grid and true north instead arises from the map reference. Consequently, “ninety degrees magnetic” and “ninety degrees grid” describe different lines on the ground where those north directions differ. If the receiver uses the number with the wrong north reference, they shift the observed direction and the area in which they look for the person or reference feature.
Angular unit and relative reference
In full-circle notation with true north as the zero reference, degrees run clockwise: east at ninety degrees, south at one hundred and eighty, and west at two hundred and seventy. A full circle contains three hundred and sixty degrees. Military directions can also use mils. In a circle divided into six thousand four hundred mils, a quarter turn is one thousand six hundred mils. The number ninety represents different angles in these two units; a report therefore needs the actual unit and, for mils, the agreed circle division.
A relative bearing instead begins at another expressly defined direction, such as a vehicle's heading or the direction in which the person is facing. “Thirty degrees to the right of my facing direction” means something different from “thirty degrees from north”. If the person turns, their relative angle to the stationary tower changes. “On my right” and “on your right” can also refer to opposite sides. Such a reference must identify whose facing direction or vehicle heading is meant.
Reciprocal direction, position and course
A reciprocal or back bearing denotes the opposite direction along the same line. For a short local reference line using the same direction reference, ninety degrees becomes two hundred and seventy degrees in the reverse direction. The reciprocal direction still gives no distance: many possible locations lie along the line. A relative position report additionally needs the clearly known reference point and a usable distance.
A bearing to a point does not specify a route through the terrain. It describes where that point lies from the origin; a course describes an intended direction of movement. An impassable rock face, a body of water or ground controlled by the adversary may lie between the two places. Reading an observed target direction as an instruction to move straight towards it would disregard those obstacles and the threat.
Measurement, estimate and report
A measured angle, a rough direction estimate and an assumption must remain distinguishable. Without a usable instrument or known north reference, seeing the arrangement of two features does not produce a measured magnetic bearing. The observation can still be described concretely: “From my viewpoint, the tower stands to the right of the pale rock pinnacle.” This identifies the features seen and the person's viewpoint without inventing an unknown angle from north.
Even when a direction value is available, the quality of the underlying information matters. It must be clear when the reference feature is uncertain, the angle is estimated or the person has left the place from which the observation was made. At greater distances, the same angular error produces a larger lateral discrepancy. Extra digits remove neither this error nor a wrong origin. If the person moves, the observed value therefore belongs to the halt at which it was established.
If the retained means allow contact with recovery forces, the direction is passed in the jointly established format. US Army PR preparation includes reference points and agreed bearing and distance formats. The person states or confirms the reference actually used and identifies estimated values; a received direction is interpreted from the same origin, reference direction and angular unit. The spatial report and authentication serve different purposes: the bearing describes a direction, while authentication checks the identity of the person behind the contact.