Transcript Chapter 7: Planning to Avoid Danger

The Weekend Navigator
Part II
Copyright 2008 Coast Guard Auxiliary Association, Inc.
Chapter 7: Planning to Avoid
Danger
Chapter 7: Planning to Avoid
Danger
• Where you do NOT want to go
• Avoidance techniques using GPS with
paper or digital charts
Define the Area
• How large an area you want to pre qualify
• Know the characteristics of hazards
• Clearly mark hazards and enter information
into GPS
Mark the Obstacles
• Isolated hazards
– Wrecks, submerged pilings, rocks
– Plot a radius of 1/10th mile or 600 feet
• Hazardous regions
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Rock outcroppings
Encompass a large area
Draw a circle or boundary around the area
Enter center points into your GPS
Mark the Obstacles
• Shoals
– Cover far more extensive area
– Shoal characteristics determine its degree of
danger
– Always check your depth criterion
Mark the Obstacles
• Bands of clear area
– Use crosstrack error
to define safe areas
– Indicate the distance
right or left of current
position from an active
course line
– Create a band of
– chosen width centered on an active line between
two waypoints
Mark Landmarks
• Using ranges (or Clearing lines)
– Use two charted objects that define an edge
rather than the center of the channel
– Used where navigation aids are not present
Mark Landmarks
• Using danger bearings
– Use only one visible, charted landmark or
ATON from which a line is drawn across the
safe side of the hazard
– Challenge is determining
whether the safe side
needs to be less than or
more than the danger
bearing
Mark Landmarks
• Using danger circles
– Circle of position (COP) requires knowing your
distance from a charted object
– Measure the radius of the arc and stay outside
the radius