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 3 The Basic Technique  GPS is your primary position sensor  Ship’s Compass for Steering  Seaman’s Eye to keep in touch with surroundings  Hand-Bearing Compass to take bearings  Plot GPS Position at regular intervals (~1hr) Verify position via independent means

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

© 2004, “The Weekend Navigator” Slide 8 Ship’s Compasses Courtesy: Ritchie Front Reading Top Reading

© 2004, “The Weekend Navigator” Slide 9 Sailboat Compasses Courtesy: Ritchie Top ReadingBulkhead Mounted Angle of Heel Sailboat compasses have different Dampening than powerboat compasses

© 2004, “The Weekend Navigator” Slide 10 Hand Bearing Compasses Courtesy: Ritchie, Davis, Plastimo

© 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…

© 2004, “The Weekend Navigator” Slide 13 Boat Effects on Compass In one direction the metallic mass may have little effect on the local magnetic field In another direction the metallic mass may have a much greater effect 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 Ref: WN Ch 28 – Measuring Compass Deviation using GPS

© 2004, “The Weekend Navigator” Slide 16 Correcting True to Compass T rue V ariation M agnetic D eviation C ompass W E add West going down or.. subtract East add East going 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°

© 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

© 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

© 2004, “The Weekend Navigator” Slide 24 Parallel Rules

© 2004, “The Weekend Navigator” Slide 25 Parallel Rules with the Compass Rose read magnetic Bearing directly

© 2004, “The Weekend Navigator” Slide 26 Using a Rolling Parallel Rule read magnetic Bearing directly

Slide 27 Exercise 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 = 066 V = 015W M = 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 = 066 V = 015W M = 081 T = 267 V = 015W M = 282 C 282M

Slide 30 T = 267 V = 015W M = 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 = 220 V = 015W T = 205 C 220M

Slide 31 M = 220 V = 015W T = 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 220M M = 029 V = 015W T = 014 C 029M

Slide 32 Cruise  Begin – Part I of Cruise Cruise is in 5 parts One part with each of remaining sessions

Slide 33 Questions ? … Comments