COMPASS

COMPASS NOTES

COMPASS

  • Courses on charts are always plotted "True"; North is 000° or 360°
  • All courses are expressed with three digits
  • Variation and deviation are expressed with one or two digits
  • Converting from True to Compass:
    • *T*rue
    • *V*ariation
    • *M*agnetic
    • *D*eviation
    • *C*ompass
    • add for Westerly variations, substract for Easterly
  • Converting from Compass to True:
    • *C*ompass
    • *D*eviation
    • *M*agnetic
    • *V*ariation
    • *T*rue
    • substract for Westerly variations, add for Easterly

VARIATION

  • Caused by earth’s magnetic forces
  • Changes in different locations of the world
  • US West coast variation is always EAST of True
  • Local variation is printed in the center of compass roses

DEVIATION

  • Caused by ferrous metals aboard the vessel and generally located less than three feet from the compass
  • Can change by the heading of the vessel; different heading, different deviation