Lines of Position (LOP)

Navigational lines drawn on a chart, each representing a possible location of a vessel based on a single observation or measurement. 

A line of position (LOP) is a fundamental concept in marine navigation used to determine a vessel’s location. It is a line on a nautical chart along which a ship is known to be positioned, based on an observation such as a bearing to a known object, a celestial sighting, or a depth contour. When two or more LOPs intersect, they create a fix, which provides a more precise position. Common methods for obtaining LOPs include taking compass bearings to landmarks, using radar ranges, or employing celestial navigation techniques. The accuracy of a fix depends on the precision of the measurements and the angle at which the LOPs intersect, with angles closer to 90 degrees providing the most reliable results. LOPs are essential for safe navigation, allowing mariners to confirm their position and adjust their course accordingly.