section d-5 plotting and labeling 1. objectives the student will: learn how to use the cps plotter...
TRANSCRIPT
Section D-5 Plotting and Labeling
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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
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The New Mk II Plotter
• Used to measure TRUE directions on a chart
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Plotting Shapes
North Arrow ALWAYS points North
(using Lat/Lo lines)
Clear tape allows navigator to mark and measure
distances
The New Mk II Plotter
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Boat symbol indicates
direction of travel
Arrow points to Reciprocal reading
on Plotter Rose
Grid Lines
Arrow indicates direction of
Bearing
Reading the Scales
Longitude Chart Line
Points True North
Parallel to Longitude
Line
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90° TRUE100°
Magnetic
Variation
10° West
Reading the Compass
Rose
090°270°
000°
180°
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Finding the TRUE & Magnetic course between two points
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C 300/ 320 M
A
B
300° True
NORTH
Variation20° West
320°Magnetic
S 10.0
Aid
We want to go 040° True from the aid
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C 0
40/ 0
20 M
Turn the Plotter Rose
to the direction 040°Variation20° East020°
Magnetic
S 10.
0
130
True Bearing of 130°
/ 110 M
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Aid
Turn the Plotter Roseto the bearing 130°
NORTH
Bearings go UNDER the line
Variation20° East
110° Magnetic
Drawing Parallel Lines
.
NORTH
Plotter Roseindicates a bearing of
340°
Required distance
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Parallel Lines
Bearing of 340° should
be maintained on plotter
Orig
inal L
ine
New
Lin
e
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)
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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
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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
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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
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Labelling Charts
• A FIX
• A DR position
• Course Line– course in TRUE & Magnetic – speed
• LOPs
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XKnown position = FIX
C 045 / 055 M
S 6.0
Always draw lines from FIXes
The FIX
A FIX is plotted as a dot inside a small circle
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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
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0900
C 045 / 055 M
S 6.0
0800
The DR Position
Note how all symbols have a dot marking the EXACT position
0700
FIX
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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
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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
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Finding the Compass Course to Steer
CDMVT
To steer0
in this course
T plus or minus
V
From
compass rose
From
Course Plot
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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
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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
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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
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0947
1000Measured distance
Using the measured distance (D),
And the time (t) it took to get to that bearing
you would find the Speed Made Good (SMG)
with 60D=St
Using your speed (s) and measured distance (D),
you would find the time (t) expected to get to that bearing from the FIX
with 60D=st
Add the time to the FIX time to get ETA
C 0
39 /
019
M
25
S 10.
0
C 054 / 034
MS 6.0
18
00
17
00
18
43
347 / 327 M
2000
1843
1852
091 / 071 M
1900
C 0
23 /
003
MS
6.0
2100
C 119 / 099 M
2034
S 6.0
You are the navigator on a boat coming into port at dusk on a wet and very windy night.
You draw a line from your last FIX on a course of 054°T to the buoy CS 47.
You plot DRs as every whole hour approaches.
At 1843, you spot a buoy ahead and think you are on track.
You take a bearing of 347° True on a TV tower
You take a bearing of 091° True on a chimney.
FIX
You realize the buoy straight ahead is CS 48 which marks an area of foul ground.
At 1852, you alter course to 023°, again heading for buoy CS 47.
You mark DRs for every whole hour.
At 2034, you pass close aboard CS 47 and change course to 119° to follow the range into the harbour.
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Keeping a LOG
• To maintain a permanent record of the cruise
• Enter– times– courses steered– bearings– FIXes– ETAs– Latitude & Longitude
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LOG
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