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Plotting and Labelling

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					          Section D-5
Plotting and Labeling


                        1
Objectives

The student will:
• Learn how to use the CPS plotter
• Know how to label course lines, LOPs, DR positions,
  Fixes
• Know the required standards of accuracy for
  chartwork
• Be able to plan a cruise




                                                        2
The New Mk II Plotter
• Used to measure TRUE directions on a chart




                                               3
Standards of Accuracy

• For directions
   – to the nearest degree
   – in 3 digits (e.g. 075)


• For time
   – to the nearest minute
   – in 4 digits (e.g. 1345)




                               11
Standards of Accuracy continued
• For distances
   – to the nearest tenth of a nautical mile
   – 10.1 nm

• For positions expressed as latitude and longitude
   – to the nearest tenth of a minute
  L 43° 21.3‟ N
  Lo 123° 10.5‟ W

• For speed
   – to the nearest tenth of a knot
   – 5.2 kn



                                                      12
Planning a Cruise
• Establish a point of departure
   – determine an accurate fix
   – aid “close aboard” means boat is at the aid
      • use dot (or circle) at base of charted aid
      • charted dock can be point of departure


• Establish a destination
   – a clearly identifiable location marked on the chart and
     recognizable from boat
   – last part of any cruise is done through conning


• Plot on chart



                                                               13
Plotting and Labelling Chart
• Look for marked hazards
   – plot around them


• Track is the line showing the intended path of the
  boat.

• TRUE Course equals the Track unless
  compensating for wind or current
   – no wind or current in this course




                                                       14
Labelling Charts

• A FIX

• A DR position

• Course Line
  – course in TRUE & Magnetic
  – speed


• LOPs




                                15
The DR Position

• Plotted
   –   at any convenient time interval
   –   every hour on the hour
   –   when change in course
   –   when change in speed
   –   when a bearing is taken


• Usually plotted only one hour ahead of the boat‟s
  position




                                                      17
LOPs

• Drawn TOWARD the object from seaward

• Time is placed on the „north‟ side of the line (FIX
  does not require LOPs labeled with time).

• Direction of Bearing (in True) is placed on the „south‟
  side of the line followed by a slash and the Magnetic
  Bearing




                                                            19
Finding the Expected Duration

• Measure along the course line from the point of
  departure to the destination

• For Speed
   – powerboats, assume most economical cruising speed
   – sailboats, estimate from direction and force of wind


• 60D=St , solve for t




                                                            20
Selecting Aids and Landmarks

• Study chart to find aids and landmarks you can use
  for either conning or plotting

• Identify possible LOPs
   – ranges, lights, steep cliffs, points of land in line, towers,
     steeples, depths




                                                                     22
Using LOPs

• LOPs drawn parallel with the track can give an
  indication of “cross-track error”
   – the boat‟s distance to the left or right of the track


• On the water, a back bearing on the point of
  departure will give an early indication if the boat is
  on track
   – calculate reciprocal, (boat track = +/- 180)
   – if back bearing equals reciprocal, boat on course
   – if back bearing less than reciprocal, boat is off course to left (Left
     Less)
   – if back bearing greater than reciprocal, boat is off course to right



                                                                              23
Using LOPs continued

• An LOP that cuts the track can give an estimate of
  the distance travelled from the last known position
  (FIX)

• By taking time into account, determine
   – ETA
   – Speed Made Good




                                                        24
Keeping a LOG

• To maintain a permanent record of the cruise

• Enter
   –   times
   –   courses steered
   –   bearings
   –   FIXes
   –   ETAs
   –   Latitude & Longitude




                                                 27
L
O
G




    28

				
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posted:10/8/2011
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