1. NAVIGATION TRAINING Section 4 Compass
The Canadian Coast Guard Auxiliary Pacific Region has made a substantial contribution to boating safety in Canada through their successful adaptation of the United States Coast Guard Auxiliary’s Coastie program to the Canadian environment, in the form of the Bobbie the Safety Boat program.

2. Table of Contents • Section 1 Types of Navigation
• Section 2 Terrestial Coordinates
• Section 3 Charts
• Section 4 Compass
• Section 5 Nautical Publications
• Section 6 Navigational Aids
• Section 7 Buoyage
• Section 8 Position Lines and Fixes
• Section 9 Tides
• Section 10 Currents
• Section 11 Weather

3. Compass Types of Compasses • Magnetic Compass
A compass that senses direction by interaction between its own permanent magnets and the earth’s magnetic field.
• Gyroscopic Compass
A electrical gyroscopic that is designed to seek true north

4. Compass
Compass Rose
Sometimes called a windrose, is a figure on a compass, map, nautical chart or monument used to display the orientation of the cardinal

5. Compass

6. Compass Directional Reference Systems
Relative Bearings (˚R) = bearings measured with reference to the ship’s longitudinal axis
Magnetic Bearings (˚ M) = bearings measured with respect to magnetic north.
True Bearings (˚ T) = bearings measured with respect to true of geographic north.
Ship’s Head (or heading)= a special bearing denoting the direction in which the ship is pointing.

7. Compass
000ºT
True Bearings
270ºT
090ºT
180º T

8. Compass
Magnetic Bearings
000ºM
Variation Easterly
270ºM
090ºM
180º M

9. Compass
270ºR
Relative Bearings
180ºR
000ºR
090º R

10. Compass Port Beam Right Astern Dead Ahead Starboard Beam
Relative Bearings
Dead Ahead
Starboard Beam
Port Beam
Right Astern

11. Compass Magnetic Compass Error: Variation
• Variation is the angle between a magnetic line of force and a geographic (true) meridian at any location on the earth.
• Variation exists because the earth’s magnetic and geographic poles are not in the same location.
Magnetic anomalies in the earth’s crust also contribute to variation.

12. Compass
Magnetic
North Pole
True North Pole
Notice that the two poles aren’t together. The magnetic compass points to the magnetic pole, and this gives us VARIATION.

13. Compass Magnetic Compass Error: Variation
Variation also changes from year to year as the earth’s magnetic poles tend to wander.
Variation is printed inside compass roses on all navigation charts.
Always use the compass rose nearest your current Dead Reckoning position.
Variation changes as an observer moves along the globe.
However, if a ship moves in such a way that the meridians remained constant, it would be moving along an isogonic line - a line along which variation remains constant.

14. Compass Magnetic Compass Error: Variation
The amount that the Variation changes annually is called the Annual Change.
The amount of Annual Change is to be found on every compass rose on the chart, next to the Variation, and is normally expressed as 004°W 1995 (8’E).
To calculate change in 2008, multiply 8’E by 13 (years from 1995) 104’ or 1.75°E
Apply 1.75°E to Variation of 004°W = 2.25°W

15. Compass
Magnetic Compass Error: Variation

16. Compass Magnetic Compass Error: Deviation
•This is the angle between the magnetic meridian and the north line on the compass card.
•Deviation is caused by the interaction of the ship’s metallic structure, electrical systems, metallic objects (such as a cell phone left close to the compass) with the earth’s magnetic field.

17. Compass
Deviation
A ship’s compass also must deal with magnetic forces from the ship itself, e.g. magnets, electrical cabling. The sum total of these forces pulls the compass slightly away from magnetic north, producing DEVIATION.

18. Compass
Deviation
Deviation will change in size, dependant upon the course of the vessel.
Swinging of the ship and proper correction using soft and/or permanent magnets , deviation can be minimized.

19. Compass Compass Conversions Compass to True 1. C D M V T (AE)
Can Dead Men Vote Twice (at elections)?
2. C A D E T
Compass Add East True

20. Compass Compass Conversions
Convert Compass Courses to True Courses - this also applies to bearings, using the deviation for the vessel’s head.
Compass Course
145˚ C
Deviation
2˚W
Magnetic Course
143˚M
Variation
22˚E
True Course
165˚T

21. Compass Compass Conversions Converting True to Compass T V M D C (AW)
True Virgins Make Dull Companions (At Weddings)

22. Compass Compass Conversions
Convert True Course to Compass Course - this also applies to bearings, using the deviation for the vessel’s head.
True Course
165˚ T
Variation
22˚E
Magnetic Course
143˚M
Deviation
2˚W
Compass Course
145˚C