# PowerPoint Presentation - Pentagon Sailing Club

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```					Bay Navigation II

Lines of Motion
Set & Drift
Lines of Position
Points of Position
PPT-2

Standard Labeling Conventions
C 146 M
Lines of Motion:            course direction:

speed:          S 4.5

1535
Lines of Position (LOP):                time:

direction:          210

Points of Position:
1710
Dead Reckoning (DR)       Running Fix (R-FIX)                 R-FIX

Fix (FIX)           1050

Estimated Position (EP)
GPS Fix (GPS-FIX)                   1325
PPT-3

Standard Labeling Conventions

Course to Steer

Course to steer
corrected for leeway

Track or

Current Vector
PPT-4

The process of estimating the ship’s position
on the chart relative to its last accurately
determined position, using only:
- course
- speed
- elapsed time
PPT-5

Line of Motion: The DR Track
Labeled with course (3-digit M or T) above, and speed below (in knots).

Depicts the course the boat is steered, and its
speed through the water. Originates at a Fix or
Running Fix (R-Fix).

1315
PPT-6

DR Point of Position: An approximation of
the ship’s position along a DR track, using speed
and elapsed time to calculate distance from last
known Fix or R-Fix.

Plot a DR position:
1. every Hour on the Hour
2. at every Change in Course
3. at every Change in Speed
4. for every Line of Position (LOP)
5. for every Fix or R-Fix
Start a New DR track from every Fix or R-Fix
PPT-7

1. Plot a DR position every hour on the hour

ST
To determine distance:   D = 60
PPT-8

2. Plot a DR position at every change in course

ST
To determine distance:   D = 60
PPT-9

3. Plot a DR position at every change in speed

ST
To determine distance:   D = 60
PPT-10

In-class Practical #1:
At 2130, in close proximity to Thomas Point
Light, you head south towards R“84A”, NW
of Poplar Island. Your boat speed is 6.0 Kts.

a. Plot the DR track using standard notation
PPT-11

1. Plot FIX.

2. Plot Track.

3. Determine & label
Course.

4. Label Speed.

5. Determine & label
DR Position for 2200
(Rule #1).
PPT-12

. Plot a DR position for every Line of Position

Line of Position (LOP): A line along which
the observer (and, thus, the boat) is located, as
determined from a single observation of a
known charted object.
Types of LOPs:
1. Bearing
2. Range
3. Advanced LOP (covered under Running Fix)
PPT-13

Bearing: the horizontal direction from the
observer to a charted object, as determined by
compass.

Light

FL 6s 58ft 9M        Plot a DR position
for the time of the LOP.
[ D = (S X T) / 60 ]
D = (6.5 X 35) / 60
D = 3.8
PPT-14

Range: the horizontal direction from the observer
to two charted objects in alignment

Plot a DR position
for every LOP

Iso G
6s 41ft

Iso R
10s 113ft
PPT-15

Coincidental (non-ATON) Ranges
Tank

Spire

Plot a DR position
for every LOP
PPT-16

Estimated Position #1: An estimate of the ship’s
position along a DR track, based on a single LOP
and a DR position.
The EP of the boat is the
point where a line drawn
perpendicular to the LOP,
intersects the DR position
for that LOP.

Indicate the EP with a box
PPT-17

In-class Practical #2:
At 2210, enroute to R“84A”, you take a Bearing
of 070M off of Bloody Point Light.

a. Plot this LOP.
b. Plot your EP.
PPT-18

1. Plot the LOP.

2. Plot the DR position
for the LOP.

3. Determine and plot
the EP.
PPT-19

5. Plot a DR position for every Running Fix or Fix.

5a. Running Fix
Steps:
1. Given a DR track from the last known Fix,
take a bearing on a charted object and draw
LOP #1.
2. Mark the DR position for LOP #1.
PPT-20

Running FIX: steps 1 and 2.

Light

FL 6s 58ft 9M

1400
PPT-21

Running Fix
3. After at least 20 minutes (to allow for
sufficient separation between LOPs), take
a second bearing on the same ATON and
Draw LOP #2 on the chart.
4. Mark your DR position for LOP #2.
PPT-22

Running FIX: steps 3 and 4.

Light

FL 6s 58ft 9M

1400
PPT-23

Running Fix
5. Determine the distance traveled between
the DRs for LOP #1 and LOP #2.
6. Measure this same distance from the point
where LOP #1 intersects the DR track. Mark
the end point of that distance on the track.
PPT-24

Running FIX: steps 5 and 6.

Light

FL 6s 58ft 9M

1400
PPT-25

Running Fix

7. Draw a line parallel to LOP #1 through
the endpoint just marked on the track.
Label this advanced LOP with both the
original time and the time it was advanced.
PPT-26

Running FIX: step 7.

Light

FL 6s 58ft 9M

1400
PPT-27

Running Fix

8. The point where the advanced LOP and
LOP #2 cross is the Running Fix position.
Mark this point with a circle and label as
“R-FIX” with the time.
9. Begin a new DR track (with course and
speed noted) from the R-FIX.
PPT-28

Running FIX: steps 8 and 9.

Light

FL 6s 58ft 9M

1400

R-FIX 1440
PPT-29

In-class Practical #3:
At 2230, R“84A” is abeam to port. You change
course to 250 M, and reduce speed to 5.0 kts.
On this course, you can just make out the light
from G“83” ahead to port. At 2250, your first
LOP on G“83” is 180M; at 2310, your second
LOP on G“83” is 125M.
a. Continue standard notation of your DR track.
b. Plot a Running Fix and new DR track.
PPT-30

2230
1. Plot the FIX and the
new DR track.

2. Plot the 1st LOP and
its DR position.

3. Plot the 2nd LOP and
its DR position.

4. Advance LOP #1.

5. Plot the R-FIX and the
new DR track.
PPT-31

5. Plot a DR position for every Running Fix or Fix.

5b. Fix: a determination of the ship’s
position along a track -
1. Based on two or more LOPs taken
simultaneously, OR
2. Based on close proximity to a charted
object.
PPT-32

Fix based on two or more LOPs taken
simultaneously

Tank

Light
FL 6s 58ft 9M

1030
PPT-33

Fix based on close proximity to a charted object
(usually when it’s abeam)
PPT-34

In-class Practical #4:
Continuing from the R-FIX, at 2325 you take
a Bearing to port on Fl G 2.5s 21ft 4M “1”
and get 212 M. At the same time, you take a
Bearing to starboard on Fl G 4s 15ft 4M “1”
and get 290 M.
a. Plot the Fix and new DR track.
PPT-35

1. Plot the 1st Bearing.

2. Plot the 2nd Bearing.

3. Plot the DR position.

4. Plot the FIX and the
new DR track.
PPT-36

REVIEW: The Six Rules of Dead Reckoning

Plot a DR Position:
1. every Hour on the Hour
2. at every Course Change
3. at every Speed Change
4. for every Line of Position (LOP)
5. for every Fix or R-Fix
6. Start a New DR Track from every Fix or R-Fix
PPT-37

“Best-to-Least” Scale of Reliability
for Determined Points of Position

1. Fix (FIX)
2. Running Fix (R-FIX)
3. Estimated Position (EP)
4. Dead Reckoning Position (DR)
…but DR is better than nothing!
PPT-38

Current Sailing

• You don’t always go directly in the
direction you plan
• Known or unknown current (rivers &
tidal currents)
• Wind (leeway)
• Steering inaccuracy
• Undetermined compass error
PPT-39

Current Triangles
• Set - S
– the direction of current or leeway
• Drift - D
– The speed of current
Estimated (known)                           Actual current triangle
current triangle          Target location
C
Track
PPT-40

Correcting for Known Set and Drift
Determine the course to GC “7” from your Fix near GC “5”.
Assume a boat speed of 5.0 kts. The known current has a
set of 130M, and a drift of 1.5 kts.
SET = Direction of Current DRIFT = Speed of Current

Steps:
1. Plot and label the Track from the point
of departure to GC “7”
GC “7”

GC “5”
PPT-41

Correcting for Known Set and Drift
2. From the point of departure, plot the Set & Drift Line
for 1 hour (1.5 kts/hr = 1.5nm; the distance you
would drift in 1 hr).
SET = 130 M
DRIFT = 1.5 kts
GC “7”
GC “5”
PPT-42

Correcting for Known Set and Drift
3. Plot a Boat Speed Line from the Set & Drift Line
that intersects the Track line in 1 hour at the
current speed (5.0 kts/hr = 5.0 nm; thus the
distance traveled).

4. Determine course.
GC “7”
GC “5”
PPT-43

Correcting for Known Set and Drift
5. Plot the DR track parallel to the Boat Speed line.
6. Plot a DR position for 1 hr from the point of
departure.

GC “7”
GC “5”
PPT-44

Correcting for Known Set and Drift
7. From the 1 hr DR, draw a line parallel to the
Set & Drift line to determine the EP.
T = (60 X 0.9) / 5.0
8. Advance the EP and use DR to               T = 11 min

calculate the estimated time
of arrival at GC “7”.

GC “7”

GC “5”

Thus, steering a course of 085M
will result in a Track of 100M to
GC“7”, with an ETA of 1401
PPT-45

Estimated Position #2: An estimate of the ship’s
position along a DR track, based on a DR position
corrected for known Set and Drift.
SET = Direction of Current
DRIFT = Speed of Current
For this example,
the set of the current is 160M
and the drift is 1.0kts

From the 1300 DR position, the boat’s
Estimated Position is 1.5 NM in the
direction of 160 M, due to the elapsed time
(1 ½ hrs) from the last known Fix
PPT-46

Calculating Actual Set and Drift
DR

The vessels fixed position at any time
will always be offset from the
corresponding position in the direction
of the set of the current by the distance
the drift would have carried the vessel
during the time periodonding DR
PPT-47

Actual Set & Drift
DR

• The actual set can be determined simply by
measuring the direction of a fix from the
corresponding DR position at any time.
• The actual drift can be determined by measuring
the distance form the DR to the fix position, and
then dividing this distance by the number of hours
elapsed
• It is easier using an hour fix point
PPT-48

In-class Practical #5:
You depart R 2 in Annapolis on a course for
Bloody PT at 1000. Your boat speed is 5.0
kts. At 1100 you take the following bearings:
Thomas Pt Light 319M
Curtis PT          268M
Bloody PT Light 192M
1.   Plot a DR course
2.   Plot the 1100 fix
3.   Calculate actual set & drift
4.   Determine actual course and speed
PPT-49

1.   Plot the D from R
2 to Bloody PT
2.   Plot 1100 fix.
3. Determine set &
drift.
4.   Plot the Track
5. Determine course
and speed over
ground
PPT-50

Danger Bearings

Preplotted “limiting” LOPs drawn
in advance on a chart to help
position a boat away from a
known charted hazard.
PPT-51

+
+ + +
+ + +
+ + +
+ + +
Where
do you
make
the turn?
3

3

3

3
Danger Bearings
3
PPT-52

In-class Practical #6:
At 1100, you fix your position as abeam of R
86 on course 178 M and speed of 5.0 Kts.
Your destination is Eastern Bay. Your draft
is 6 ft.
a. Plot your DR track.
b. Plot a Danger Bearing for the turn into
Eastern Bay.
PPT-53

1. Plot the FIX and DR
track.

2. Plot the Danger
Bearing.
PPT-54

• Global Positioning System (GPS) is a
up of 24 satellites.
• GPS receivers use triangulation to
calculate the user's exact location.
• GPS receivers are accurate to ~30m or
3m, depending upon your equipment.
PPT-55

Variations on the theme
PPT-56

Setting up the GPS

• Set GPS to same datum as your
charts (generally WGS 84)
• Set GPS to magnetic heading
• Set GPS to Nautical Units
(nautical miles and knots)
PPT-57

• Read lat/lon from GPS
• Use dividers to plot lat/lon
on chart
• Plot using GPS-Fix symbol
and establish new course
line
PPT-58

Establishing Waypoints
• Plan a safe course to
destination on chart
• Determine lat/lon coordinates at
each course change (waypts)
• Enter waypt coordinates into
GPS
PPT-59

Navigating to Waypoints
• Use “Goto” to navigate to each waypoint
• Use “Map” or “Highway” view to stay on course and
monitor progress
• Double check using traditional piloting techniques
PPT-60

Creating Routes
• A route is a collection of
waypoints
• Route-capable GPS offers
several options to create and
edit routes:
• Select previously established
waypoints
• Create waypoints in map view
• Upload from chart software
PPT-61

Electronic Charts
PPT-62

Integrated Systems
PPT-63

Integrated Systems

• Enable linkages between the GPS, chart
plotter and auto-pilot
• Allow for the auto-pilot to maintain
course based on waypoints previously
set in the GPS
PPT-64

When using an integrated system,
NEVER use an ATON’s exact position as a
GPS waypoint!
PPT-65

Conclusion
Piloting and navigation skills, once gained,
stay with you only through practice.
The more you practice, the easier these
skills will come to you when most needed
(i.e., when the electronics go out, when
visibility is reduced, when your skipper or
crew is incapacitated).
Practice, practice, practice!

```
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 views: 4 posted: 2/10/2012 language: pages: 65