In celestial navigation, what does the term "LOP" stand for?

In celestial navigation, "LOP" stands for "Line of Position." This term refers to a line that represents all the possible locations where a vessel could be, based on celestial observations such as sightings of stars, the sun, or other celestial bodies. When navigators take measurements and plot them, they create a line rather than a specific point, indicating the uncertainty in their exact position.

The Line of Position is important because it allows sailors to determine their location relative to visible celestial bodies and, when multiple lines of position are used together, can lead to a more accurate fix of their actual position at sea. In practice, a navigator typically takes several sightings and creates multiple LOPs that intersect, helping to pinpoint the vessel's true location more precisely. This technique is a cornerstone of traditional navigation, especially before the advent of modern GPS technology.