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Piloting Course Chapter 4
On-the-Water
United States Power Squadrons ®
Slide 2
Responsibilities of the Skipper
You are responsible for the safety of• Your crew• Your boat
Consequently, you decide on navigation• Use the techniques that ensure your safety
The Piloting Course provides the tools• It’s up to you to decide how to apply them
Slide 4
View from the Water
Learn to recognize ‘on-the-water’ views• Navigation Aids• Landmarks• Land Features
Study charts so you know what to look for
Practice on clear days so you know the landscape when it turns foul
Slide 5
Use GPS as Primary Position Sensor
Properly Set Up GPS• Chart Datum -- WGS 84 (or other as
required)• Latitude & Longitude (grid)
Degrees, Minutes, Tenths of Minutes for most coastal charts
Degrees, Minutes, Seconds for many inland charts
• Magnetic reference (preferred, auto set)
• Nautical Units Matches the chart (coastal)
– Nautical Miles (nm) & Knots (kn) Statute units (Great Lakes and inland charts)
– Statute Miles (mi) & Miles per Hour (mph)
Slide 6
Use the Compass for Steering
GPS is NOT a compass• It provides direction based on movement
history• Will not work in static situation
Compass is easier to steer with• May need to use GPS to get oriented• Then, read and follow the compass heading
Slide 7
Attributes of a Quality Compass
Repeatability• Always returns to the same reading• When, returned to the same heading
or, when temporarily diverted using a magnet or metallic object
Damping• Turns smoothly on your boat• Sail & Powerboat compasses are
different
Largest you can afford• Easier to read, smoother movement• Top Reading, preferred
© 2003, R J Sweet, “GPS for Mariners.” Reprinted with permission© 2004, “The Weekend Navigator”
Slide 8
Ship’s Compasses
Courtesy: Ritchie
Front Reading
Top Reading
© 2003, R J Sweet, “GPS for Mariners.” Reprinted with permission© 2004, “The Weekend Navigator”
Slide 9
Sailboat Compasses
Courtesy: Ritchie
Top Reading Bulkhead Mounted
Angle of Heel
Sailboat compasses have differentDampening than powerboat compasses
© 2003, R J Sweet, “GPS for Mariners.” Reprinted with permission© 2004, “The Weekend Navigator”
Slide 10
Hand Bearing Compasses
Courtesy: Ritchie, Davis, Plastimo
© 2003, R J Sweet, “GPS for Mariners.” Reprinted with permission© 2004, “The Weekend Navigator”
Slide 11
Compass Binoculars
Slide 12
Errors Affecting Compasses
Metallic Objects• Alter local magnetic fields• Can cause compass errors
Current-carrying Wires• Create their own magnetic fields• Interfere with Earth’s field near
compass
Compass Error – called DEVIATION• Dependent upon heading of boat• How to Measure – Appendix B
The boat’s effect on the compass…
© 2003, R J Sweet, “GPS for Mariners.” Reprinted with permission© 2004, “The Weekend Navigator”
Slide 13
Boat Effects on Compass
In one direction the metallicmass may have little effect on the local magnetic field
In another direction the metallicmass may have a much greatereffect on the local magnetic field
Slide 14
DEVIATION
Compass can be adjusted• Counteract local deviation using • Compensating magnets in compass
Compass Adjusting• Recommend a professional adjuster
Residual Deviation• Even after compensation – some
deviation• May need to correct compass readings to
magnetic (or vise-versa)
Slide 15
Deviation Table
Table of Corrections
Deviation Table
Magnetic to Compass Compass to Magnetic
Magnetic Degrees
Deviation Degrees
Magnetic Degrees
Deviation Degrees
Compass Degrees
Deviation Degrees
Compass Degrees
Deviation Degrees
000° 1°W 180° 0° 000° 1°W 180° 0° 045° 2°W 225° 2°E 045° 2°W 225° 2°E 090° 2°W 270° 1°E 090° 2°W 270° 1°E
135° 1°W 315° 1°E 135° 1°W 315° 1°E
Ref: WN Ch 28 – Measuring Compass Deviation using GPS
© 2003, R J Sweet, “GPS for Mariners.” Reprinted with permission© 2004, “The Weekend Navigator”
Slide 16
Correcting True to Compass
TTruerue
VVariationariation
MMagneticagnetic
DDeviationeviation
CCompassompass
WW EEadd Westgoing down
or.. subtract East
add Eastgoing up
Slide 17
Remembering the Correction
remember…
When converting from True to Compass
• “West is Best” – add West
• “East is Least” – subtract East
Slide 18
Practical Compass Use
Typical Compass• 5° - graduated increments• Read to about 2-3°
Properly corrected compass• Residual Deviation typically < 2°• Ignore Deviation for moderate runs
Slide 19
Fluxgate Compass
Economical Electronic Compass
Uses electronics to sense the magnetic field
Self-compensating• automatically builds deviation table• automatically applies deviation to reading• continuously updates deviation table
Extremely Accurate• Typically < 1°
© 2003, R J Sweet, “GPS for Mariners.” Reprinted with permission© 2004, “The Weekend Navigator”
Slide 20
Fluxgate Compass
Slide 21
Plotting Magnetic
4 x 15 Plotter uses Grid Lines• Oriented to True not Magnetic• Requires conversion
Alternative• Use Compass Rose• Inner scale is oriented to Magnetic• Parallel rules
© 2003, R J Sweet, “GPS for Mariners.” Reprinted with permission© 2004, “The Weekend Navigator”
Slide 22
Compass Rose
Slide 23
SKILL – Using the Compass Rose
Chart Compass Rose provides• Variation• Scale calibrated to Magnetic
Can be used to plot courses
SKILL• Plot & label courses & bearings using
the compass rose
© 2003, R J Sweet, “GPS for Mariners.” Reprinted with permission© 2004, “The Weekend Navigator”
Slide 24
Parallel Rules
© 2003, R J Sweet, “GPS for Mariners.” Reprinted with permission© 2004, “The Weekend Navigator”
Slide 25
Parallel Rules with the Compass Rose
read magneticBearing directly
© 2003, R J Sweet, “GPS for Mariners.” Reprinted with permission© 2004, “The Weekend Navigator”
Slide 26
Using a Rolling Parallel Rule
read magneticBearing directly
Slide 27
Exercise 4-1 - Using Compass Rose
Use Bowditch Bay Chart
Follow instructions in Student Guide• Measure magnetic courses using the
Compass Rose
Slide 28
Exercise 4-1
Plotting with rectangular course plotter and parallel rules using the Compass Rose.
Plot a course from G “7” Fl G 4s Main Channel to G “5” Fl G 4s GONG Main Channel. Measure and label the magnetic course using parallel rules and the nearest compass rose.
C 081M
T = 066V = 015WM = 081
Slide 29
Exercise 4-1
Plotting with rectangular course plotter and parallel rules using the Compass Rose.
Plot a course from G “7” Fl G 4s Main Channel to G “5” Fl G 4s GONG Main Channel. Measure and label the magnetic course using parallel rules and the nearest compass rose.
Plot a course from R “6” Fl R 4s Main Channel to R “8” I Q R Main Channel using the rectangular course plotter and the nearest compass rose.
C 081M
T = 066V = 015WM = 081
T = 267V = 015WM = 282
THE OUTER SCALE IS READ FROM A
MERIDIAN OF LONGITUDE. THE
INNER SCALE FROM A PARALLEL
OF LATITUDE.
090
270
180
000
080 070060
050
040
030020
01000
0
260 250240
230
220210
209190
180
100
110
120
130
140
150
160
170
180
280290
300
310
320
330
340
350
360
170 160 150140
130
350 340 330 320
310
190200
210
220
230
010020
030
040
050
C 282M
Slide 30
T = 267V = 015WM = 282
Exercise 4-1
Plotting with rectangular course plotter and parallel rules using the Compass Rose.
Plot a course from G “7” Fl G 4s Main Channel to G “5” Fl G 4s GONG Main Channel. Measure and label the magnetic course using parallel rules and the nearest compass rose.
Plot a course from R “6” Fl R 4s Main Channel to R “8” I Q R Main Channel using the rectangular course plotter and the nearest compass rose.
Plot and label a course of 220º magnetic from R “4” Fl R 6s BELL Main Channel using the rectangular course plotter and the nearest compass rose.
C 081M
C 282M
M = 220V = 015WT = 205
THE
OU
TER
SC
ALE
IS R
EA
D F
RO
M A
ME
RID
IAN
OF
LON
GIT
UD
E. T
HE
INN
ER
SC
ALE
FR
OM
A P
AR
ALL
EL
OF
LATI
TUD
E.
090
270
180
000
080
070
060050
040 030 020 010000
260
250
240230
220 210 209 190180
100
110
120
130
140
150
160
170
180
280
290
300
310
320
330
340
350
360
170
160
150140
130
350
340
330 320 310
190
200
210
220
230
010
020
030
040
050
C 2
20M
Slide 31
M = 220V = 015WT = 205
Exercise 4-1
Plotting with rectangular course plotter and parallel rules using the Compass Rose.
Plot a course from G “7” Fl G 4s Main Channel to G “5” Fl G 4s GONG Main Channel. Measure and label the magnetic course using parallel rules and the nearest compass rose.
Plot a course from R “6” Fl R 4s Main Channel to R “8” I Q R Main Channel using the rectangular course plotter and the nearest compass rose.
Plot and label a course of 220º magnetic from R “4” Fl R 6s BELL Main Channel using the rectangular course plotter and the nearest compass rose.
Plot and label a course of 029º magnetic from G C “1” Perkins Cove using parallel rules and the nearest compass rose.
C 081M
C 282M
C 2
20M
M = 029V = 015WT = 014
C 0
29M
Slide 32
Cruise
Begin – Part I of Cruise
• Cruise is in 5 parts
• One part with each of remaining sessions
Slide 33
Questions ? … Comments