Line of Position (LOP)

A line on which an observer’s position must lie according to one measured bearing, range, angle or other observation.

Examples include a bearing line to a charted object, a radar range circle, a depth contour under suitable conditions or a celestial position line. Two independent LOPs may intersect at a fix, while three can reveal inconsistency as a cocked hat.

Accuracy depends on object identification, geometry, timing, instrument and plotting error. LOPs taken at different times require allowance for vessel movement before they are combined.

Terms with the same meaning:
Position Line