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					Bay Navigation II




   Lines of Motion
     Set & Drift
  Lines of Position
  Points of Position
Electronic Navigation
               Bay Navigation II
                                                                      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



          Bay Navigation II
Standard Labeling Conventions

Course to Steer

Course to steer
corrected for leeway

Track or
Course made good


Current Vector
                                                PPT-4


            Bay Navigation II

         Dead Reckoning (DR)
The process of estimating the ship’s position
on the chart relative to its last accurately
determined position, using only:
  - course
  - speed
  - elapsed time
                   Bay Navigation II
                                                                      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
              Bay Navigation II
                                                    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
           Bay Navigation II
                                               PPT-7




1. Plot a DR position every hour on the hour




                                       ST
          To determine distance:   D = 60
             Bay Navigation II
                                                  PPT-8




2. Plot a DR position at every change in course




                                         ST
            To determine distance:   D = 60
             Bay Navigation II
                                                 PPT-9




3. Plot a DR position at every change in speed




                                         ST
            To determine distance:   D = 60
            Bay Navigation II
                                                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
                  Bay Navigation II
                                      PPT-11




1. Plot FIX.


2. Plot Track.


3. Determine & label
   Course.

4. Label Speed.

5. Determine & label
   DR Position for 2200
   (Rule #1).
              Bay Navigation II
                                                    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
                    Bay Navigation II
                                                          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
             Bay Navigation II
                                                 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.
                    Bay Navigation II
                                        PPT-18




1. Plot the LOP.


2. Plot the DR position
   for the LOP.


3. Determine and plot
   the EP.
              Bay Navigation II
                                                  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
           Bay Navigation II
                                               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
             Bay Navigation II
                                                  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



             Bay Navigation II

               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
            Bay Navigation II
                                                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
             Bay Navigation II
                                                  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.
                          Bay Navigation II
                                                     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.
              Bay Navigation II
                                                 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)
           Bay Navigation II
                                              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.
                           Bay Navigation II
                                               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.
             Bay Navigation II
                                                  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
          Bay Navigation II
                                       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



           Bay Navigation II

          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


                        Bay Navigation II

                       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
    Speed of Advance
                       Bay Navigation II
                                                                          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”
                  Bay Navigation II
                                                             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”
                 Bay Navigation II
                                                          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”
                 Bay Navigation II
                                                           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”
                 Bay Navigation II
                                                                        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
                       Bay Navigation II
                                                                                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
          Bay Navigation II
                                             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



               Bay Navigation II
           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
               Bay Navigation II
                                                 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
                      Bay Navigation II
                                          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
        Bay Navigation II
                                   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
            Bay Navigation II
                                               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.
                         Bay Navigation II
                                             PPT-53




1. Plot the FIX and DR
   track.

2. Plot the Danger
   Bearing.
                Bay Navigation II
                                           PPT-54




            Electronic Navigation
• Global Positioning System (GPS) is a
  satellite-based navigation system made
  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.
           Bay Navigation II
                               PPT-55




Variations on the theme
               Bay Navigation II
                                   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)
               Bay Navigation II
                                    PPT-57




        Determining your position
• Read lat/lon from GPS
• Use dividers to plot lat/lon
  on chart
• Plot using GPS-Fix symbol
  and establish new course
  line
              Bay Navigation II
                                     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
              Bay Navigation II
                                                  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
              Bay Navigation II
                                    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
Bay Navigation II
                    PPT-61




Electronic Charts
 Bay Navigation II
                     PPT-62




Integrated Systems
         Bay Navigation II
                                           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
         Bay Navigation II
                                          PPT-64




 When using an integrated system,
NEVER use an ATON’s exact position as a
            GPS waypoint!
           Bay Navigation II
                                               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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