Definition

Noun: A fixed reference line marked on a compass or a sighting device, used to indicate the forward heading or bearing of a ship or aircraft. It serves as an alignment mark against which the compass card is read.

Usage

The lubber line is a fundamental navigational aid. It is physically inscribed on the compass housing or a sighting instrument. The navigator aligns the vessel's bow with this line, and the compass card reading directly opposite the lubber line indicates the current heading.

Examples

• The captain checked the compass, ensuring the ship's bow was aligned with the lubber line to read an accurate heading of 270 degrees.
• To take a bearing, turn the compass until the lubber line points directly at the landmark.
• The pilot adjusted the aircraft's course until the desired heading was directly under the lubber line.

Advanced Usage

• "To read against the lubber line": To determine a heading by observing which compass card marking is aligned with the fixed lubber line.
  • The helmsman steered by reading the course against the lubber line.

Variants and Related Words

• Lubber's point: Another term for the lubber line, emphasizing its function as a reference mark.
• Lubber's line: A common variant spelling of "lubber line."

Synonyms

• Reference line
• Heading marker
• Index line

Related Phrases

• Lubber line error: A navigational error caused by misalignment between the vessel's centerline and the lubber line, or by not sighting directly over the line.
  • Incorrect installation can cause a permanent lubber line error.

Noun

1. a fixed line on a ship's compass indicating its heading