Terrestrial Magnetism - Ch 10

Question 1

DRC / DIC

Answer 1

Direct Reading/Indication compass - looking directly at the sensor and the display

Driven by earths magnetic field - lines of flux

Question 2

Magnetic EQ

Answer 2

Halfway between the magnetic Poles

Question 3

Magnetic Dip

Answer 3

The angle between the freely suspended magnet and the horizontal (local)

Horizontal Component - H
Vertical Component - Z

Question 4

H Component

Answer 4

Max: EQ
Min: Magnetic Poles

DRC is useless at high latitudes and most efficient at the EQ

Question 5

Magnetic EQ (dip)

Answer 5

0 Dip

Question 6

Aclinic Line

Answer 6

A Line of 0 dip

Question 7

Isoclinal Line

Answer 7

Line of equal dip

Question 8

Variation

Answer 8

The difference between the true north and the magnetic north

Max 180 degrees
Where the magnetic lies relative to the true

Question 9

Deviation

Answer 9

Angular difference between the compass heading and the magnetic north

Caused by the ACs own magnetic field - ferrous material / electrical circuits
Error changes depending on heading

Question 10

Compass Swings

Answer 10

Used to reduce deviation in the DRC

Errors are shown on compass deviation / residual card

Question 11

When do you perform compass swings

Answer 11

Periodically 
Latitude base changing
Long period of parking
Major equipment change 
Suspected error
Lightening strike 
Carrying large ferrous/magnetic cargo