piloting tips and techniques 85
- Choose a danger bearing. Pick a charted, visually prominent object such
that a line drawn through the object will skirt the shoal’s near edge at its far
end and pass near your approach point at its near end. Th is is your danger
bearing. Draw short tick marks along the line pointing toward the side of the
danger (see illustration). Th is helps the danger bearing stand out from other
lines, such as your trackline. - Determine the direction of the danger bearing. Measure the direction
to the object twice to confi rm the bearing. Convert a true bearing to a
magnetic bearing by applying variation (add westerly or subtract easterly
variation). Label the top of the danger bearing line with the magnetic
danger bearing (045°M in the illustration). - Prefi x the danger bearing. If the danger lies to starboard of the bearing, use
the prefi x NLT (not less than) in front of the danger bearing. If the hazard
lies to port, use the prefi x NMT (not more than). In the illustration we write
NLT in front of the danger bearing of 045 degrees magnetic. As long as your
bearing to the tank reads more than 045 degrees, you’ll pass safely. If it reads
045 degrees or less, you need to turn left until you cross the danger bearing.
RADAR DANGER RANGES AND CIRCLES OF POSITION
Radar-equipped vessels oft en use predetermined range settings to clear shoals.
As discussed earlier, lines of position are actually parts of circles. Compare a
As long as the bearing to the tank reads more than 045 degrees magnetic, you will clear the
shoal to starboard. If the bearings start to decrease, turn left to cross the danger bearing
line and return to safe water.