1. Advanced Piloting Course Chapter 5 Positioning Techniques
United States Power Squadrons ®
Advanced Piloting Course Chapter 5 Positioning Techniques
Introduce USPS and what we do
Introduce the Instructor(s) and Proctors
Explain the logistics for the session

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

3. Plotting Position Position provided by GPS Basic technique
…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

4. Plotting Coordinates You must plot the GPS coordinates on a chart
GPS indicates:
L 38° 53.0 N
Lo 94° 49.3 W
You must plot the GPS coordinates on a chart
38° 53.0´ N
As in the earlier example, you need to plot your position to know where you are. There are two techniques that we will show.
In the first, you plot the coordinates from the latitude and longitude scales as shown.
94° 49.3´ W
©2003, “GPS for Mariners”, Reprinted with Permission

5. Plotting GPS Position
Figure Plotting GPS Position – You can plot your GPS position by using a pair of dividers. First, set the latitude using one point of the dividers and place the second point on the nearest grid line. Then transfer this distance across the chart to your approximate location. Make a light pencil mark. Second, repeat the process for the longitude. Make sure that you read the numbers accurately and select the appropriate point on the latitude and longitude scales.
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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!

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
Plot using Grid Line Crossing
Using GPS coordinates

8. Plotting Distance and Bearing
GPS indicates:
Bearing 20°
Distance 1.2nm
The GPS provides continuous updates of Distance & Bearing to the Waypoint
Distance 1.2 nm
Bearing 20°
An alternative technique uses the GPS provided Bearing and Distance to the waypoint to plot location. You simply draw a line going through the Waypoint at a 20° angle to the grid line, and then mark off the distance of 1.2 nm along that line. That is your location.
This technique is less likely to produce and error and it is more intuitive than plotting coordinates. It’s also quicker.
This approach is quicker, more intuitive, and less prone to error than plotting coordinates
©2003, “GPS for Mariners”, Reprinted with Permission

9. Position by Bearing & Distance
Figure Position by Bearing and Distance – An even better and more intuitive approach uses another feature of the GPS, namely, the distance and bearing from your current location to a waypoint. If you place a protractor plotting tool over the waypoint and set the reciprocal reading on the arm, you can draw the bearing line and measure the distance directly to your position.
You will need to set the protractor arm to the magnetic bearing if you have set up your GPS to magnetic direction. You can do this by converting the magnetic to true or use a plotting tool with a variation scale incorporated on the arm as shown. You can make your own distance scale by making pencil marks on the protractor arm using the latitude scale.
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10. Plotting the GPS Bearing

11. Plotting a Waypoint Bearing
Using a Protractor Plotter
Place over waypoint
180° on top
Line-up with bearing
Adjust for variation
variation scale
some plotters have an
index arm with a
variation scale
protractor scale
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12. Using Plotter with Variation Scale
180° up
next, plot
distance to waypoint
center on
waypoint
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13. Exercise 5-1 – Plot Bearing & Distance
Get out Bowditch Bay chart
Plot a fix using bearing & distance
SOLUTION

14. Solution to Exercise 5-1

15. Using Bearings to Waypoints
©2003, “GPS for Mariners”, Reprinted with Permission

16. Using Distances to Waypoints
©2003, “GPS for Mariners”, Reprinted with Permission

17. Using Grid Line Crossing
©2003, “GPS for Mariners”, Reprinted with Permission

18. Using the Compass Rose as Waypoint
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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

20. Using Radar to Avoid Danger
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21. Using Radar for Distance Off
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22. Exercise 5-2 – Radar distance off
Get out Bowditch Bay chart
Radar VRM indicates distance off
Can be used to provide an LOP

23. Solution to Exercise 5-2
Exercise 5-2
Radar
Distance
Off

24. Positioning with Seaman’s Eye
Using Ranges
Avoiding Collisions

25. Ranges Ranges are Pre-Plotted Bearings Uses Very Precise
Use two visible charted landmarks
Bearing line intersects both landmarks
Uses
Navigation in narrow channels
Alignment with Harbors
Formal navigation aids
Can build own to help navigate
Very Precise

26. Formal Range

27. Informal Range

28. Range Pictures

29. Using a Range to Check your Compass
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30. Convenient Range to Harbor
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31. Collision Bearing – 3D View
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32. Collision Bearing – from the Boat 1
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33. Collision Bearing – from the Boat 2
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34. Collision Bearing – from the Boat 3
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35. Other Boat Passing Ahead – 3D View
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36. Other Boat Passing Behind – 3D View
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37. Plotting Underway using GPS
Normal plotting
Converting to Dead Reckoning

38. Plotting GPS Fixes Underway
Visual bearing
GPS Fix
Visual bearing
Figure Plotting GPS Position on a Chart – While on a cruise, particularly when venturing into unfamiliar waters, you should plot your GPS position on a chart on a regular basis. The actual frequency depends upon your speed and local features. The primary reason that you do this is to have a reference point should your GPS fail, or visibility degrades. At the same time that you plot and label your GPS position on the chart, you should attempt to verify the GPS by taking a visual bearing to an active waypoint.
GPS Fix
Visual on buoy
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39. Transition to Dead Reckoning
Bearing and DR
Position as a check
GPS Fix
Bearing doesn’t match
Fix from bearings
Proceed by Dead Reckoning
GPS Fix
Visual on buoy
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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

41. Graphical Definition of Data Fields
Figure Graphical Definition of GPS Data Fields – Your GPS provides a variety of data fields that can assist in your navigation tasks. The names may vary slightly from one model to another, but the geometry of these data fields is relatively common. From your current location, indicated by the boat in the graphic, your actual path over ground is indicated in red and is known as your TRACK or COG (Course Over Ground). Your SPEED is your actual speed over ground, also called (Speed Over Ground). The direct path to the ‘active to waypoint’ is shown in orange. The associated data fields are BEARING and DISTANCE to Waypoint and VMG (Velocity Made Good). Your original COURSE is shown in green. This is the path that you intended to take. Your OFF COURSE distance is shown in yellow. This is also known as Crosstrack Error. Your Heading is the only information that the GPS does not have.
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42. Situation – GPS data fields
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43. Using Crosstrack Error to stay safe
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44. Optimizing Progress while Tacking
Challenge for Sailors
Selecting the best heading
Considering boat performance relative to the wind
Tuning the sails to the wind
Racers use polar diagrams
You can use your GPS, here’s how…

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
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46. Using GPS Velocity Made Good - 1
Boat Speed
– determined by polar diagram
VMG
– determined by vectors
Wind
GPS
– provides real-time indication
of VMG
Destination

47. Using GPS Velocity Made Good - 2
Boat Speed
– higher in this direction
VMG
– higher even though pointed
farther from destination
GPS
– provides real-time indication
of VMG
Destination

48. Using GPS Velocity Made Good - 3
Boat Speed
– still higher in this direction
VMG
– lower due to geometry
GPS
– provides real-time indication
of VMG
Destination

49. Using VMG - heading steer for max VMG VMG 45° 50° 55°
boat heading from wind

50. Using VMG – sail set adjust for max VMG VMG too loose too tight

51. Tacking at 45° to Wind
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52. Tacking at 50° to wind
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53. Using GPS VMG Don’t need theory Adjust for maximum VMG Results
No polar diagrams
Adjust for maximum VMG
Adjust heading
Adjust sails
Results
Optimum pointing and sail configuration
Real time adaptation to changes in winds

54. Final Tack – Bearing to Mark
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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

56. Exercise 5-3 Conditions
075°M

57. Possible Solutions to Exercise 5-3

58. Questions ? … Comments
Surely, you have questions.