Transcript Plotting and Labelling

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
The New Mk II Plotter
Clear tape allows navigator
to mark and measure
distances
North Arrow ALWAYS
points North
(using Lat/Lo lines)
Arrow indicates
direction of
Bearing
Boat symbol
indicates
direction of travel
Grid
Lines
Arrow points to
Reciprocal reading
on Plotter Rose
Plotting Shapes
4
Reading the Scales
90° TRUE
Points True
North
Parallel to
Longitude
Line
Variation
10°
West
100°
Magnetic
Longitude
Chart Line
5
000°
270°
180°
Reading the
Compass
Rose
090°
6
Finding the TRUE & Magnetic course between
two points
300° True
N
O
R
Variation
T
20° West
H
320°
Magnetic
B
A
7
We want to go
040° True from
the aid
020°
Variation
20° East
Turn the Plotter Rose
to the direction 040°
Magnetic
Aid
8
True Bearing of
130°
N
O
R
T
H
Bearings go
UNDER the line
Aid
Turn the Plotter Rose
to the bearing 130°
110°
Magnetic
Variation
20° East
9
Drawing
Parallel Lines
.
Required
distance
N
O
R
T
H
Parallel Lines
Bearing of
340° should
be maintained
on plotter
Plotter Rose
indicates a
bearing of
340°
10
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 FIX
Always draw lines
from FIXes
X
Known position = FIX
A FIX is plotted as a dot
inside a small circle
16
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
The DR Position
Note how all symbols have a
dot marking the EXACT position
FIX
0700
18
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
Finding the Compass Course to Steer
T
V
M
D
C
From
Course Plot
From
compass rose
T
plus or minus
V
0
in this course
To steer
21
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
Using the measured
distance (D),
Using your speed (s) and
measured distance (D),
And the time (t) it took to
get to that bearing
you would find the time (t)
expected to get to that
bearing from the FIX
you would find the Speed
Made Good (SMG)
with 60D=st
with 60D=St
Add the time to the FIX time
to get ETA
1000
Measured distance
0947
25
You
realize
buoy
You
are you
thethe
navigator
on a
At
2034,
pass
close
AtYou
1852,
you
alter
course
to
1843,
draw
a line
spotfrom
a buoy
your
straight
ahead
is
CS
48
You
mark
DRs
for
every
boat
coming
into
port
at
You
take
a
bearing
of
347°
plot
DRs
as
every
091°
aboard
CS 47
and change
023°,
again
heading
ahead
last FIX
and
onthink
a course
youfor
are
of on
FIX
which
marks
area
of foul
whole
hour.
dusk
on
a119°
wet
and
very
True
hour
on
aan
approaches.
TV
tower
course
to
chimney.
to
follow
the
buoy
CS
054°T
to47.
the buoy CS 47.
track.
ground.
windyinto
night.
range
the harbour.
1843
2034
1700
1800
2000
1900
1852
091 / 071 M
26
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