NAV - Magnetism & Compasses Flashcards
What is True North? (1)
The direction that points directly towards the geographic North Pole
What is Magnetic North? (2)
- The direction that a compass needle points to as it aligns with the Earth’s magnetic field
- Magnetic North Pole shifts and changes over time in response to changes in the Earth’s magnetic core
What is Magnetic Variation? (2)
- AKA Magnetic declination
- The angle between magnetic north and true north
What is Magnetic Declination? (2)
- Changes over time and with location
- Compass points with local magnetic fields, a declination value is needed to obtain true north
What is Deviation?
The angle between Magnetic North and Compass North measured in degrees East or West from Magnetic North
What do Magnetic Compasses suffer from? (3)
- Manufacture error
- Irregularities
- Fluctuations in Earth’s Magnetic Field
What is an Isogonal line? (1)
Magnetic variation shown on a map, with Lines across a map joining points of equal variation
What is a Marginal Diagram? (1)
Shows True North (TN) and Magnetic North (MN) and the angle between them
What is a Double Compass Rose? (1)
A large compass rose aligned to TN and a
smaller inset compass rose aligned to MN
What is Compass North? (1)
Magnetic north corrected for deviation
Deviation Card diagram
MN to TN Variation calculation example (1 of 2)
The aircraft is heading 178°M.
If the variation is 7°E, what is the true heading?
“Variation east magnetic least, variation west magnetic best”
MN to TN Variation calculation example (2 of 2)
The aircraft is heading 287°M.
If the variation is 11°W, what is the true heading?
“Variation east magnetic least, variation west magnetic best”
MN to TN Deviation calculation example
The aircraft is heading 185°M.
If the deviation is 7°E, what is the compass heading?
“Deviation east compass least, deviation west compass best”
Compass variations Practice questions
(Answers on slide 18/25)
