A line connecting points having the same astronomical longitude. Because the deflection of the vertical (station error) varies from point to point, the astronomical meridian is not a plane curve. When the astronomical meridian is corrected for station error, it becomes the GEODETIC MERIDIAN. Also called TERRESTRIAL MERIDIAN and sometimes called GEOGRAPHIC MERIDIAN.

Related Terms

RESTRICTOR

A device for producing a deliberate pressure drop or resistance in a line by reducing the cross-sectional flow area.

SPREAD

The divergence of the air stream in a horizontal or vertical plane after it leaves the outlet.

SPREAD

The divergence of the air stream in a horizontal or vertical plane after it leaves the outlet.

GRID RHUMB LINE

A line making the same oblique angle with all grid meridians. Grid parallels and meridians may be considered special cases of the grid rhumb line.

HAND LEAD

A light sounding lead (7 to 14 pounds), usually having a line of not more than 25 fathoms

GROUND LOG

A device for determining the course and speed over the ground in shallow water consisting of a lead or weight attached to a line. The lead is thrown overboard and allowed to rest on the bottom. The course over ground is indicated by the direction the line tends and the speed by the amount of line paid out in a unit of time.

GYROSCOPIC DRIFT

The horizontal rotation of the spin axis of a gyroscope about the vertical axis

HEAVE

The oscillatory vertical rise and fall, due to the entire hull being lifted by the force of the sea. Also called HEAVING

CASE DRAIN FILTER

A filter located in a line conducting fluid from a pump or motor housing to reservoir.

ELASTOHYDRODYNAMIC LUBRICATION

In rolling element bearings, the elastic deformation of the bearing (flattening) as it rolls, under load, in the bearing race. This momentary flattening improves the hydrodynamic lubrication properties by converting point or line contact to surface-to-surface contact.

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