A compass depending for its directive force upon the attraction of the horizontal component of the earth’s magnetic field for a magnetized needle or sensing element free to turn in a horizon tal direction. 
A compass depending for its directive force upon the attraction of the horizontal component of the earth’s magnetic field for a magnetized needle or sensing element free to turn in a horizon tal direction. 
Related Terms 

VIBRATING NEEDLEA magnetic needle used in compass adjustment to find the relative intensity of the horizontal components of the earth’s magnetic field and the magnetic field at the compass location. Also called HORIZONTAL FORCE INSTRUMENT. 
COEFFICIENT AA component of magnetic compass deviation of constant value with compass heading resulting from mistakes in calculations, compass and pelorus misalignment, and unsymmetrical arrangements of horizontal soft iron. 
DIRECTIVE FORCEThe 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 
MAGNETIC MERIDIANA line of horizontal magnetic force of the earth. A compass needle without deviation lies in the magnetic meridian. 
COEFFICIENT EA component of magnetic compass deviation varying with the cosine function of twice th 
COEFFICIENT CA component of magnetic compass deviation, varying with the cosine function of the compas 
COEFFICIENT BA component of magnetic compass deviation, varying with the sine function of the compas 
COEFFICIENT DA component of magnetic compass deviation, varying with the sine function of twice th 
MAGNETIC DIPAngular 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. 
GAUSSIN ERRORDeviation of a magnetic compass due to transient magnetism caused by eddy currents set up by a changing number of lines of force through soft iron as the ship changes heading. Due to these eddy currents, the induced magnetism on a given heading does not arrive at its normal value until about 2 minutes after change to the heading. This error should not be confused with RETENTIVE ERROR. 
MarineProHelp 2018.