Navigation
Learning Objectives
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Explain the differences between pilotage and dead
reckoning.
List at least 7 items of equipment for diving navigation.
List at least 6 aids to natural navigation.
List at least 5 ways to measure distance underwater
and state which is most accurate.
Compare the following: heading, bearing, course, and
fix.
Describe variation and deviation and state the cause
and effect
of each.
Explain how to circumnavigate an underwater
obstacle.
Contrast true north and magnetic north.
Main Points
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Methods of Navigation
Measuring Distance Underwater
Natural Navigation
Fixing a position
Compass Navigation
Methods of Navigation
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Pilotage
– Confirming location using visual checkpoints
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Dead Reckoning
– Estimating position based on distance and
direction.
– This system requires keeping track of
speed, time, and direction of travel.
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Combination
– Using one system to confirm the other
Measuring Distance Underwater
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Measured line/tape measure
– most accurate
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Arm spans
Kick cycles
Air consumption
Time
Natural Navigation
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Underwater landmarks
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Ripple Marks
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parallel to the wave front
deeper/steeper ripples = waves feel bottom more
ripples closer together = waves closer together
Surge
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pick something permanent.
typically onto and off of shore
strongest toward shore
Currents
Bottom contours
Sunlight or changes in light
Fixing Position
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Ranges
– Establishes 1 line of position (LOP)
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Fixes
– Use multiple lines of position to establish
position
Compass Navigation
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Terminology
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True North
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Magnetic North
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Point near the North Pole towards which a compass needle
points.
Variation
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Geographic North pole
Local differences between True and Magnetic North.
Deviation
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Difference between Magnetic and Compass North.
Caused by
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Metal
Magnetic source
Compass Navigation cont.
– Bearing
• Angular direction from an object expressed in
degrees. Bearings may be expressed in terms of
True, Magnetic, Compass or relative degrees.
– Heading
• A course followed or to be followed
– Leeway
• Sideways slipping due to wind or current.
Compass Navigation Cont.
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Uses of a compass
– Follow a specified heading/direction/course
– Establish bearing/direction to an object
– Fix position
Compass Navigation Cont
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Parts of a compass
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North seeking needle
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Compass card
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card with course numbers always points north
Lubber line
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needle always points
used to determine direction of travel
Sights
Index marks
Rotating Bezel
Navigators window
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allows you to read the course from the side of the compass
Provides actual compass course
Compass Navigation Cont
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Siting a course
– best way is to site across the compass
– alternatively align lubber line with center of
diver and desired course.
Compass Navigation Continued
• Patterns
– Straight line/reciprocal
– Squares/Rectangles
– Triangles
– Circumnavigating
• 90° turns
• Constant distance
Compass Navigation Cont
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Common Errors
– Not paying attention
– Compass not level
– Not believing the compass and following
your nose
– Compass pointed in the wrong direction
– Not keeping track of distance
Compass Navigation Cont.
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Miscellaneous Equipment
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Slates
Markers
Floats
Compass board
Charts
Main Points
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Methods of Navigation
Measuring Distance Underwater
Natural Navigation
Fixing a position
Compass Navigation
Learning Objectives
•
•
•
•
•
•
•
•
Explain the differences between pilotage and dead
reckoning.
List at least 7 items of equipment for diving navigation.
List at least 6 aids to natural navigation.
List at least 5 ways to measure distance underwater
and state which is most accurate.
Compare the following: heading, bearing, course, and
fix.
Describe variation and deviation and state the cause
and effect
of each.
Explain how to circumnavigate an underwater
obstacle.
Contrast true north and magnetic north.