Advanced Piloting Course

Chapter 4Avoidance Techniques

United States Power Squadrons ®

Slide 2

Navigation from a different Perspective

What you have learned:• Point-to-point navigation

Primary technique in Piloting & AP Pre-qualify the path, follow the path

Alternative & complementary approach• Navigating to avoid

Avoid shallow water Avoid hazards Avoid restricted areas

• Chapter 4 Danger Bearings, Circles Avoidance Techniques

Slide 3

First Step

Determining what to avoid• Examine chart for region of interest• Identify:

Region for boating» Limits of latitude and longitude» Harbors or bays

Hazards» Rocks» Obstacles» Shallow water

Charted, visible reference points» Navigation aids» Landmarks

© 2003, R J Sweet, “GPS for Mariners.” Reprinted with permission© 2004 “The Weekend Navigator”

Slide 4

Determining the Avoidance Area

Slide 5

Danger Bearings

Intent:• By monitoring bearing to a landmark

Stay away from danger

SKILL• Plotting and Labeling Danger Bearings• Monitoring the bearing on the water

Slide 6

Constructing a Danger Bearing

Slide 7

Constructing a Danger Bearing

Slide 8

Constructing a Danger Bearing

Slide 9

Constructing a Danger Bearing

Slide 10

Constructing a Danger Bearing

Slide 11

Constructing a Danger Bearing

Slide 12

Constructing a Danger Bearing

Slide 13

Constructing a Danger Bearing

Slide 14

Constructing a Danger Bearing

Slide 15

Constructing a Danger Bearing

Slide 16

Constructing a Danger Bearing

Slide 17

Constructing a Danger Bearing

Slide 18

Monitoring Position

Danger Bearings

• Visual bearings Hand-bearing compass Monitor bearing to landmark

• GPS bearings Enter landmark as waypoint Monitor GPS bearing to landmark

© 2003, R J Sweet, “GPS for Mariners.” Reprinted with permission© 2004 “The Weekend Navigator”

Slide 19

Using Danger Bearings

Slide 20

Danger Sector

Slide 21

Exercise 4-1 – Danger Bearing

Take out Bowditch Bay chart

Plot and label danger bearing

Slide 22

Solution to Exercise 4-1

Slide 23

Crosstrack Error

Feature in GPS

• Data Field Indicates deviation from course line Left or Right of intended course Distance in feet or nautical miles

• Alarm An alarm can be set Sounds if exceed crosstrack error

Slide 24

Crosstrack Error

Uses

• Stay close to course line

• Boat freely within lateral limits Sailing

Slide 25

Crosstrack Error – Avoid Hazards

© 2003, R J Sweet, “GPS for Mariners.” Reprinted with permission© 2004 “The Weekend Navigator”

Slide 26

Determining an Avoidance Region

rhumb line

alarm upon exit

© 2003, R J Sweet, “GPS for Mariners.” Reprinted with permission© 2004 “The Weekend Navigator”

Slide 27

Using Crosstrack Error

Slide 28

Exercise 4-2

Using Bowditch Bay chart

Plot & label – Crosstrack Error

Slide 29

Solution to Exercise 4-2

Slide 30

Danger Circles

Danger circles Similar concept to danger bearing Danger is within or outside of the circle

Measuring a danger circle• GPS

Anchor watch (stay within the circle) Avoidance waypoint (stay outside the circle) Alarmed

• Radar Monitor radius to an object Guard zone

– Alarmed

© 2003, R J Sweet, “GPS for Mariners.” Reprinted with permission© 2004 “The Weekend Navigator”

Slide 31

Avoidance Waypoint

© 2003, R J Sweet, “GPS for Mariners.” Reprinted with permission© 2004 “The Weekend Navigator”

Slide 32

Using Danger Circles

Slide 33

Danger Circles

Slide 34

Exercise 4-3 – Danger Circles

Take out Bowditch Bay chart

Plot and label – danger circle• Use radar VRM

Slide 35

Solution to Exercise 4-3

Slide 36

Putting it all Together

Slide 37

Danger Bearing - 1

Slide 38

Danger Bearing - 2

Slide 39

Danger Bearings Define Entrance

Slide 40

Alternative – GPS Bearing + XTE

Slide 41

Danger Circles

Slide 42

Putting it all Together

Slide 43

Other Avoidance Techniques

GPS

• Mark boundaries Linear boundary (artificial buoys) Cardinal boundary (N-S-E-W of danger)

Digital Chart Navigation

• Computer Create any shape for a danger area Tied to an alarm Can select exit or entrance alarm

– Alarm when leave (e.g., anchor watch)– Alarm when enter (e.g., danger area)

© 2003, R J Sweet, “GPS for Mariners.” Reprinted with permission© 2004 “The Weekend Navigator”

Slide 44

Adding Waypoints to Define Shallows

© 2003, R J Sweet, “GPS for Mariners.” Reprinted with permission© 2004 “The Weekend Navigator”

Slide 45

Alarms on a Chart Screen

© 2003, R J Sweet, “GPS for Mariners.” Reprinted with permission© 2004 “The Weekend Navigator”

Slide 46

Safe Area Alarm

Slide 47

Questions ? … Comments