Reciprocal Bearings

Making use of back-to-front compass bearings
A reciprocal bearing is the opposite of any ordinary bearing. In other words, it differs in direction from an ordinary bearing by 180 degrees.A compass bearing from a vessel to an object on shore, compared with the reciprocal bearing—a compass bearing of the vessel from the object on shore—will reveal the deviation of her compass on various headings.Light lists are given in reciprocal bearings when they make such comments as: “Shows green from 180° to 200°.” Those bearings are not the directions of the sector edges as they emerge from the lighthouse, but rather the bearings of the lighthouse as taken from a vessel. On the chart, the sector would be shown as ranging from 360° to 020°.A reciprocal bearing of a sailboat’s heading—in other words, a bearing extending aft along her centerline—may be compared to the visible wake to find the amount of leeway she is making.See also Compass Bearings; Leeway.