Advanced Piloting Course

Chapter 5Positioning Techniques

United States Power Squadrons ®

Slide 2

Positioning for the Advanced Pilot

Staying in touch is imperative

• With the surroundings Constantly looking for navigation aids and

landmarks Reference to the shoreline

• With the chart Awareness of current position

– Plotting GPS position– Comparing Radar position

Checking bearings

• Ready backup Dead reckoning and bearings

Slide 3

Plotting Position

Position provided by GPS• …but the chart tells you where you are (if you plot your position)

Basic technique• Plot latitude and longitude

Watch out for…• Incorrectly read or plot coordinates• Wrong waypoint selected in GPS

8-15© 2004 “The Weekend Navigator” Slide 5

Plotting GPS Position

Slide 6

Disadvantages to Plotting Coordinates

Folded chart• Coordinate scales not visible

Transcription errors• Coordinates are just strings of

numbers

Takes time• May rely on eye or skip entirely

Can be a big mistake!

Slide 7

Other Approaches with GPS?

Plot Bearing & Distance• To a waypoint• Using GPS data fields

Plot Bearings to 2 Waypoints• Using GPS nearest waypoints

Plot Distances to 2 Waypoints• Using GPS nearest waypoints

Plot using Grid Line Crossing• Using GPS coordinates

8-16© 2004 “The Weekend Navigator” Slide 9

Position by Bearing & Distance

Slide 10

Plotting the GPS Bearing

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

Slide 11

Plotting a Waypoint Bearing

Using a Protractor Plotter

1. Place over waypoint

2. 180° on top

3. Line-up with bearing

4. Adjust for variation

variation scale

protractor scalesome plotters have anindex arm with a variation scale

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

Slide 12

Using Plotter with Variation Scale

180° up

center onwaypoint

next, plot distance to waypoint

Slide 13

Exercise 5-1 – Plot Bearing & Distance

Get out Bowditch Bay chart

Plot a fix using bearing & distance

SOLUTION

Slide 14

Solution to Exercise 5-1

Slide 15

Using Bearings to Waypoints

©2003, “GPS for Mariners”, Reprinted with Permission

Slide 16

Using Distances to Waypoints

©2003, “GPS for Mariners”, Reprinted with Permission

Slide 17

Using Grid Line Crossing

©2003, “GPS for Mariners”, Reprinted with Permission

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

Slide 18

Using the Compass Rose as Waypoint

Slide 19

Position with the aid of Radar

Radar can support position• Fixes can be derived from point targets

Buoys– Challenge is to identify the proper return as buoy

Points of land or unique features

• Position can be deduced from shoreline echoes Shoreline echoes

– Identifiable profile – approximate position (seaman’s eye)– Relatively flat shoreline – approximate distance off

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

Slide 20

Using Radar to Avoid Danger

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

Slide 21

Using Radar for Distance Off

Slide 22

Exercise 5-2 – Radar distance off

Get out Bowditch Bay chart

Radar VRM indicates distance off• Can be used to provide an LOP

Slide 23

Solution to Exercise 5-2

Exercise 5-2

RadarDistance

Off

Slide 24

Positioning with Seaman’s Eye

Using Ranges

Avoiding Collisions

Slide 26

Formal Range

Slide 28

Range Pictures

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

Slide 29

Using a Range to Check your Compass

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

Slide 30

Convenient Range to Harbor

Slide 37

Plotting Underway using GPS

Normal plotting

Converting to Dead Reckoning

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

Slide 38

Plotting GPS Fixes Underway

GPS FixVisual on buoy

GPS FixVisual bearing

GPS FixVisual bearing

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

Slide 39

Transition to Dead Reckoning

GPS FixVisual on buoy

GPS FixBearing doesn’t match

Fix from bearingsProceed by Dead Reckoning

Bearing and DRPosition as a check

Slide 40

Monitoring Position while Sailing

Challenge• Sailing into the wind• Powering into the waves

Requires tacking rather than direct path

• Staying safe• Monitoring progress

Use GPS• Data fields

Course, Track, Bearing Crosstrack Error (XTE) VMG (velocity made good)

– Optimize progress and sails

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

Slide 41

Graphical Definition of Data Fields

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

Slide 42

Situation – GPS data fields

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

Slide 43

Using Crosstrack Error to stay safe

Slide 44

Optimizing Progress while Tacking

Challenge for Sailors

1. Selecting the best headingConsidering boat performance relative to the

wind

2. Tuning the sails to the wind

Racers use polar diagrams

You can use your GPS, here’s how…

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

Slide 45

Polar Diagram for Sailboat

As close as you can sail with this boat

You will go faster with this heading, but will it get you there faster?

You’re sailing farther away from your destination!

BOAT SPEED 7 kn

Slide 46

Using GPS Velocity Made Good - 1

Destination

Boat Speed – determined by polar diagram

VMG – determined by vectors

GPS – provides real-time indication of VMG

Wind

Slide 47

Using GPS Velocity Made Good - 2

Destination

Boat Speed – higher in this direction

VMG – higher even though pointed farther from destination

GPS – provides real-time indication of VMG

Slide 48

Using GPS Velocity Made Good - 3

Destination

Boat Speed – still higher in this direction

VMG – lower due to geometry

GPS – provides real-time indication of VMG

Slide 49

Using VMG - heading

VMG

boat heading from wind

45° 50° 55°

steer for max VMG

Slide 50

Using VMG – sail set

VMG

sail set

too loose too tight

adjust for max VMG

Slide 53

Using GPS VMG

Don’t need theory• No polar diagrams

Adjust for maximum VMG• Adjust heading• Adjust sails

Results• Optimum pointing and sail configuration• Real time adaptation to changes in

winds

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

Slide 54

Final Tack – Bearing to Mark

Slide 55

Exercise 5-3 – Route Planning

Use Bowditch Bay chart• Homework

Select a route for sailing into the wind

Make real-time on the water decisions

Sail from R N “14” on main channel To RG “D” on NE Bowditch Bay

Slide 56

Exercise 5-3 Conditions

075°M

Slide 57

Possible Solutions to Exercise 5-3

Slide 58

Questions ? … Comments