What element is crucial when determining a bearing using a ship's compass?

When determining a bearing using a ship's compass, the deviation of the compass is a crucial element. Deviation refers to the error introduced in the compass reading due to local magnetic influences on the vessel itself, typically caused by onboard metal structures and electronic equipment. This error must be accounted for to ensure accurate navigation.

A vessel's compass reads magnetic north, but due to deviation, this reading may not accurately reflect true heading. Navigators rely on deviation tables, which indicate the degree of error at different headings, allowing them to apply corrections and derive the correct bearing. Hence, understanding and correcting for compass deviation is essential for effective navigation and achieving accurate bearings.

The other aspects, such as vessel speed over ground, lines of position (LOPs) from various objects, and distance traveled, are important for overall navigation but do not directly impact the accuracy of bearing readings provided by the compass itself. While these factors contribute to situational awareness and positional fixing, they do not address the inherent errors caused by compass deviation.