Transcript Chapter 2: What is Navigation?

The Weekend Navigator
Basic Level I
Copyright 2008 Coast Guard Auxiliary Association, Inc.
What is Navigation?
• Not the same as driving your
grandparent’s car
• A major part is to avoid hazards while
traveling from Point A to Point B
• On the water, you make your own
roads!
Chapter 2: Lesson Objectives
• Piloting versus navigation
• The three steps of navigation
• Pre-voyage components
– What to include in pre-voyage planning
• Planning on the fly
• What to watch for when underway
Chapter 2: Lesson Objectives
• Double checking
• Piloting without electronics
• Using ATONs, plotting courses and
distances, dead reckoning, visual
bearings, ranges, and relative bearings
• Lesson experience using the sample
cruise experience
The Three Steps of Navigation
• Step #1: Pre-voyage planning or deciding which
path to take
• Step #2: Navigating underway or following the
selected path
• Step #3: Double-checking or confirming by
independent means that you are where you think
you are
• A skilled navigator will not
rely only on his electronic
equipment but will also use
his ship’s compass, his eyes,
charts, and other tools
What is Included in Pre-voyage
Planning?
• Charts and how to use them
• How much planning is enough?
– The kind of boating
– The waters where you will boating
– The conditions under which you will be
operating
What Will Your Voyage Look
Like?
• Proceeding directly from one point to
another?
• Tacking into wind and waves?
• Meandering freely while fishing or just
enjoying yourself?
Step #1: Pre-voyage Planning
• Consider pre-plotted charts and course
segments
• Plot your own courses
• Plot areas that you want to avoid
Step #1: Pre-voyage Planning
• Impulsive behavior can be dangerous
• Make sure to choose a safe path
• Plot your current position and locate
hazards
Step #2: Navigating Underway
• Follow your plan
• Regularly monitor your
course and progress
along your course
• Know where you are at all times!
Step #2: Navigating Underway
• How might
real-life
conditions
cause you to
stray from your
intended path?
Step #3: Double - Checking
• Remember that electronic gear is not foolproof!
• Know where you are at all times!
• What are some simple techniques for
double-checking?
Step #3: Double - Checking
• Use your seaman’s eye to confirm your
position
• Use radar and other devices to confirm GPS
readings
• Do not rely on any one device for navigation!
Piloting Without Electronics
• Navigation with the aid of landmarks,
land features, and charted navigation aids
• Try to begin and end your course at a
navigation aid
• Take bearings from your boat to a
charted object in view
Navigation Aids
Plotting Courses and Distances
• Intended course is the planned route you
will follow
• Track or line of motion is the course you
cover over ground
• What factors cause a deviation from your
intended course?
Plotting Courses and Distances
• Course direction can be measured using
a protractor
• Distance can be measured using a pair of
dividers
Estimating Your Position by
Dead Reckoning
• Dead reckoning is a way to approximate a
boat’s current position using a known
past position and intervening times,
speeds, and directions of travel
• DR plot or DR track is the result of dead
reckoning
Determining Position by
Visual Bearings
• Taking a bearing is the process of
measuring the direction to a charted
landmark you can see from boat
– Taken with a hand-held compass
• Powerful tool independent of GPS or
dead reckoning
Determining Position by
Visual Bearings
• Each bearing taken is considered a line of
position
• Your position is somewhere along your
course line, but where?
• What factors might alter your line of
position?
Determining Position by
Visual Bearings
• A fix is the intersection of two or more
bearings
– More accurate than dead reckoning
Determining Position by
Visual Bearings
• The intersection of three bearings will
form a triangle
– Your position is considered to be in the
center of the triangle
Ranges
• Any visible pair of landmarks can constitute a
range
• What might be some examples of ranges?
Ranges
• Your position will lie on the plotted range
line when the two landmarks are in perfect
alignment
• Some specifically designed navigation aids
may serve as ranges
Relative Bearings
• Relative bearing is any bearing taken with respect
to your boat
• Must be converted before plotting on your chart
• How to convert a relative bearing?
How Do We Convert
a Relative Bearing?
Converting Relative Bearings
• Consider how many degrees the relative
bearing lies clockwise from the heading of
your boat, then add that number to you
boat’s magnetic heading to get the
equivalent magnetic bearing
• Example: Boat’s magnetic heading is 30o
and a port bearing is 270o, then a port beam
bearing is 30o + 270o = 300oM (magnetic)
Sample Cruise