A = Make sure the arrow is pointing in the direction you wish to travel
B = Make sure the arrows are pointing to North on the Chart
C = Read off the bearing
Calculating effective bearings involves:
- T - True Course in Degrees,
- V - Apply Variation,
- M - to give us a Magnetic course,
- D - Apply Variation,
- C - to give us a Compass Course.
1) PICK TWO POINTS YOU WISH TO TRAVEL BETWEEN ON THE CHART
2) LINE UP THE PLOTTER BETWEEN THE FIRST AND SECOND POINT, MAKING SURE THE DIRECTION OF BEARING ARROW IS POINTING IN THE DIRECTION YOU WISH TO TRAVEL.
3) LINE UP THE COMPASS ON THE PLOTTER WITH THE GRID LINES ON THE CHART
4) TURN THE PLOTTERS COMPASS UNTIL THE N IS POINT TO NORTH ON THE CHART
5) THE NUMEBR ON THE PLOTTERS COMPASS BELOW THE 0 IS YOUR ‘TRUE’ BEARING. IN THIS EXAMPLE IT IS 291 DEGREES (TRUE)
6) CALCULATE VARIATION: LOCATE THE COMPASS ROSE ON YOUR CHART NEAREST TO YOUR POINT OF TRAVEL (BEARING)
7) IN THIS EXAMPLE: THE VARIATION MARKED ON THE CHART IS 2 DEGREES 25’ WEST.
8) TO CALCULATE VARIATION USE THE FOLLOWING:
WEST IS BEST, EAST IS LEAST. THEREFORE IF YOU HAVE AN EAST VARIATION YOU WILL ADD IT TO YOUR ‘TRUE’ BEARING. IF YOU HAVE A WEST VARIATION YOU WILL SUBTRACT IT FROM YOUR ‘TRUE’ BEARING.
IN THIS EXAMPLE:
TRUE BEARING = 291 DEGREES
VARIATION = 2 DEGREES WEST
THEREFORE MAGNETIC BEARING = 289 DEGREES (M)
9) DEVIATION: IS CAUSED BY THE MAGNETIC FIELDS GENERATED ONBOARD YOUR BOAT I.E. ENGINES, ELECTRONICS, METAL WORK ETC. EACH VESSEL WILL HAVE ITS OWN UNIQUE DEVIATION WHICH IS CALCULATED AND DETAILED ON THE BOATS DEVIATION CARD.
What is a True North?
True North is where the Longitude Lines meet at the North Pole.
What is Variation?
In a nutshell it is the difference between True North and Magnetic North.
True North is where the Longitude Lines meet at the North Pole. Magnetic North is where our compass points which is towards the Magnetic North Pole; how much variation and whether it lies to the East or West depends on where we are in the world. Variation is shown on the Compass Rose on your Chart.
What is Compass Deviation?
Deviation is created by items such as electronics, metal work, engines etc on your boat all of which create their own magnetic field which in-turn effects your compass. Every vessel will therefore have its own unique variation which can be calculated and logged on a Deviation Table.