An isoclinal; a line connecting points of equal magnetic dip.

Related Terms


A north-south reference line, particularly a great circle through the geographical poles of the earth. The term usually refers to the upper branch, the half, from pole to pole, which passes through a given place; the other half being called the lower branch. An astronomical (terrestrial) meridian is a line connecting points having the same astronomical longitude. A geodetic meridian is a line connecting points of equal geodetic longitude. Geodetic and sometime astronomical meridians are also called geographic meridians. Geodetic meridians are shown on charts. The prime meridian passes through longitude 0°. Sometimes designated TRUE MERIDIAN to distinguish it from magnetic meridian, compass meridian, or grid meridian, the north-south lines relative to magnetic, compass, or grid direction, respectively. A fictitious meridian is one of a series of great circles or lines used in place of a meridian for certain purposes. A transverse or inverse meridian is a great circle perpendicular to a transverse equator. An oblique meridian is a great circle perpendicular to an oblique equator. Any meridian used as a reference for reckoning time is called a time meridian. The meridian used for reckoning standard zone, daylight saving, or war time is called standard, zone, daylight saving, or war meridian respectively. The meridian through any particular place or observer, serving as the reference for local time, is called local meridian, in contrast with the Greenwich meridian, the reference for Greenwich time. A celestial meridian is a great circle of the celestial sphere, through the celestial poles and the zenith. Also called CIRCLE OF LATITUDE.


The magnetic equator; the line on the surface of the earth connecting all points of zero magnetic dip.


A line indicating the direction in which a force acts, as in a magnetic field


A magnetic compass in which the lubber’s line and compass card, or a portion thereof, are viewed as an image projected through a system of lenses upon a screen adjacent to the helmsman’s position.


A line of horizontal magnetic force of the earth. A compass needle without deviation lies in the magnetic meridian.


The force tending to cause the directive element of a compass to line up with the reference direction. Also, the value of this force. Of a magnetic compass, it is the intensity of the horizon- tal componen


A line connecting points of equal magnetic intensity, either the total or any component


A line through the north-south points of a magnetic compass. The COMPASS CARD AXIS lies in the compass meridian


A line joining points of no magnetic variation, a special case of an isogonic line


Angular distance between the horizontal and the direction of a line of force of the earth’s magnetic field at any point. Also called DIP, MAGNETIC INCLINATION.

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