How is a line of position established in navigation?

A line of position in navigation is established when a navigator determines a specific bearing or line of sight to an object from the current location of the boat. This can involve taking a compass bearing to a landmark or celestial body, which forms a straight line on which the vessel is assumed to be located. Typically, this line isn't a precise point but rather a width of possibilities due to inherent navigational uncertainties.

When a bearing is taken, it indicates a direction in which the vessel lies relative to the object observed. This information can then be cross-referenced with other lines of position obtained from different objects or bearings to triangulate the exact position of the boat. The idea is to create a network of lines, allowing for a more accurate determination of the vessel's location.

Other options, while they can relate to navigation practices, do not specifically define how a line of position is established. A straight path marked on the chart may indicate a course or route but does not directly denote the vessel's current position. GPS coordinates represent a precise location rather than a navigational line of position, and radar reflections serve more to provide distance from objects rather than establishing a line. Therefore, the correct answer emphasizes the fundamental navigation technique of using bearings to ascertain a position.