lubber's line
Noun: A fixed reference line marked on a compass or a compass housing of a ship or aircraft. It is aligned with the vessel's centerline (fore-and-aft line) and is used to read the vessel's heading directly from the compass card.
The lubber's line provides a stationary point against which the moving compass card is read to determine the direction the vessel is pointing. - The captain aligned the ship's bow with the buoy, checking that it matched the reading at the lubber's line. - To steer a steady course, keep the desired compass bearing directly opposite the lubber's line.
- Taking a bearing: While the primary function is for heading, a navigator can sometimes sight an object over the compass and note the compass card reading at the lubber's line to get a rough bearing.
- He took a quick bearing on the lighthouse by sighting it across the compass and reading the degree mark at the lubber's line.
- Lubber line (noun): The more common modern spelling, often without the possessive 's'.
- Ensure the lubber line is perfectly aligned with the keel during installation.
- Lubber's point (noun): A synonymous term, though less common.
- Reference line
- Heading indicator
- Index line
The term is specific to maritime and aviation navigation. It is named after "lubber," an old term for an unskilled sailor, implying it is the simple, fixed line for even a novice to use as a reference, as opposed to the moving parts of the compass.
- a fixed line on a ship's compass indicating its heading