Before revision: A position line or line of position is a line (or curve) that can be both identified on a chart (nautical chart or aeronautical chart) and observed on the surface of the earth.
After revision: (LOP), more generally, a curveA position line or line of position is a line (or curve) that can be both identified on a chart (nautical chart or aeronautical chart) and observed on the surface of the earth.