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

Emphasize used to measure TRUE directions The New Mk II Plotter Used to measure TRUE directions on a chart Emphasize used to measure TRUE directions the wheel turns 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 Build slide – goes through all of the features one by one. Dwell on the North Arrow and lat/lo lines Plotting shapes: Fix, DR, GPS, Bearing Boat and bearing direction Explain reciprocal Additional grid lines Plotting Shapes 4

Points True North Parallel to Longitude Line Reading the Scales Points True North Parallel to Longitude Line Variation 10° West 100° Magnetic Lo chart line Point to TRUE north Variation scale Multiple build 90° TRUE Longitude Chart Line 5

Reading the Compass Rose 000° 270° Reading the Compass Rose 090° Multiple build may need to repeat once or twice 180° 6

Finding the TRUE & Magnetic course between two points Variation 20° West 300° True 320° Magnetic C 300 / 320 M Place plotter in direction of travel (we are going from A to B Draw course line Align Lo line with chart Lo line Read off TRUE direction 300 deg Note VAR 20 deg W Label C300 / 320M and speed Mention the exercise on Page D43 – do on own time at home S 10.0 B A 7

We want to go 040° True from the aid Turn the Plotter Rose to the direction 040° Variation 20° East 020° Magnetic / 020 M S 10.0 C 040 We know the FIX position (close aboard charted aid “AID”) Want to travel 040 True from AID Set 040 on plotter Align plotter rose with any Lat line Align plotter edge with AID Draw course line Calculate VAR Label Aid 8

Bearings go UNDER the line True Bearing of 130° N O R T H Bearings go UNDER the line 130 / 110 M We need to travel towards a mark at a bearing of 130 TRUE Point plotter towards aid Set 130 on the plotter rose Align plotter rose line with nearest Lo line and edge of plotter with Aid Draw course line Set VAR Label bearing UNDER the line Aid 110° Magnetic Variation 20° East Turn the Plotter Rose to the bearing 130° 9

. Drawing Parallel Lines Required distance Original Line N O R T H New Line Bearing of 340° should be maintained on plotter Parallel Lines Method of finding parallel line Assume we have an existing course line Align plotter edge with the course line Align plotter rose with Lo line with rose point North Read off True direction (340) Set required distance off (how?) Slide plotter to new position while maintaining 340 set Draw new course line Plotter Rose indicates a bearing of 340° 10

Standards of Accuracy For directions For time to the nearest degree in 3 digits (e.g. 075) For time to the nearest minute in 4 digits (e.g. 1345) Directions Nearest degree (round up) For time To nearest minute In 4 digits 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 Distances Nearest 10th of a nm (10.1 nm) Lat/Long Nearest 10th of a minute Speed Nearest 10th 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 We assume two crew – one to handle navigation full time 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 LOPs course in TRUE & Magnetic speed LOPs 15

A FIX is plotted as a dot inside a small circle The FIX Always draw lines from FIXes C 045 / 055 M S 6.0 Known position = FIX X FIX – a known and charted position Dot in a circle We draw lines from the FIX Label appropriately 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 We start from a FIX – label it Label course line 0900 0800 C 045 / 055 M Note how all symbols have a dot marking the EXACT position S 6.0 FIX We start from a FIX – label it Label course line Label the DR at convenient interval – we are using 60 minutes The DOT marks the EXACT position (calculated!) 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 V T From Course Plot From compass rose T plus or minus V in this course To steer Start with “T” and ask class where we find each piece of information Slides builds with answers 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

Starting from FIX, calculate first DR and label Label course 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 039 / 019 M S 10.0 Using DR and bearings Starting from FIX, calculate first DR and label Label course Plan ahead to establish when abeam Pt Cowan light (what’s that?) Measure Distance (how?) and use what (60Dst) to calculate time to reach that position (ETA) – why ETA? When actually at bearing you can get the SMG 1000 Measured distance 0947 25

Work way through the build At 2034, you pass close aboard CS 47 and change course to 119° to follow the range into the harbour. You mark DRs for every whole hour. You take a bearing of 347° True on a TV tower At 1843, you spot a buoy ahead and think you are on track. You realize the buoy straight ahead is CS 48 which marks an area of foul ground. FIX At 1852, you alter course to 023°, again heading for buoy CS 47. You take a bearing of 091° True on a chimney. 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. 2034 2100 1843 C 119 / 099 M S 6.0 2000 1800 Refer to Fig D-5.7 in notes Work way through the build C 023 / 003 M S 6.0 347 / 327 M C 054 / 034 M 1700 S 6.0 1900 1852 091 / 071 M 1843 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 Log pages at back of notes This is the last slide 28