Section One: 4. The Magnetic Compass and Direction Flashcards
045, 135,225 and 315 degrees are what kinds of directions?
Quadrantal points
Grid north is the same as
True North
What is ‘variation’?
Angular difference between North Geographic and Magnetic Poles
Why is magnetic variation not uniform across the Earth’s surface?
Due to the angular difference between the two kinds of Poles
What is an isogonal?
Line joining locations of equal magnetic variation
What kind of variation is experienced over the UK currently?
Western
What is an agonic line?
Indication of where magnetic variation is 0
Isogonals are shown for every what increment in mag variation?
0.5 degrees
If mag north is WEST of true north (westerly direction), the magnetic direction will have a
Higher angular value than true direction
If mag north is EAST of true noth (easterly direction), the magnetic direction will have a
Lower angular value than true direction
If magnetic direction has a higher angular value than true direction, what variation exists?
Westerly
If magnetic direction has a lower angular value than true direction, what variation exists?
Easterly
Rhyme to remember for mag/true variation
Variation west - Magnetic Best, Variation East - Magnetic Least
The metallic structure and equipment of an aircraft has what effect on navigational ability?
Compass deviation occurs
Rhyme to remember for compass deviation
Deviation west - compass best, deviation east - compass least
Why is magnetic compass reliability poor near the magnetic poles?
Magnetic dip is greater
Weaker horizontal component
At what approximate latitudes does do magnetic compasses become unreliable?
60 degrees North or South