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CANADIAN COAST GUARD AUXILIARY - PACIFIC

NAVIGATION AND CHARTWORK


February 2012


Navigation and Chartwork

• This powerpoint is not intended to cover this whole subject.

• While it covers the main pertinent points of the standard, the candidate is expected to be already familiar with nautical charts, symbols, and various methods of obtaining fixes using visual means, radar and other electronic navigational aids, as well as the nautical publications.


Standard


Standard

• Comprehensive knowledge of charts, chart symbols and chartwork

• Knowledge of bearings, ranges, fixes, running fixes, set and drift

• Compass use

• Knowledge and use of nautical publications

• Navigate in all conditions with due regard for good seamanship


Chart Information


Chart Information

• Chart 1 is the publication containing explanations of the symbols, terms and abbreviations needed to interpret nautical charts published by the Canadian Hydrographic Service.

• Coxswains must be familiar with this document.

• It is available online.


Chart Information


Standard Chartwork Symbols


Descriptions


Taking Visual Fixes

• Visual fixes with bearing taken at the same time.

• Take bearings on the beam first, and those directly ahead or astern last.

• When measuring objects to determine a line of position, measure first those which have the greatest rate of change in the quantity being measured; measure last those which have the least rate of change in that quantity.


Dead Reckoning

Fix

1010 DR

1030

A method to forecast where the vessel will be, knowing true course and speed alone

Course 100T @ 30 knots 20 minutes at 30 knots = 10nm


Estimated Position

Fix

1010EP

1030

A method to forecast where the vessel will be, knowing true course and speed, set and drift

Course 100T @ 30 knots 20 minutes at 30 knots = 10nm

Set 040°T at 6 knots 20 minutes at 6 knots = 2nm


Allowing for Set and Drift

Fix

1010

A method to maintain the desired track allowing for set and drift

Set 040°T Drift 6 knots

Course to make good 100 T

Speed made good 31.5 knots

Course to steer 115TSpeed 30 knots


Running Fix

A method to find the vessel with two bearings off the same object or two different objects


Running Fix 1

A method to find the vessel with two bearings off the same object or two different objects

1000 Bearing 1 010°T

Course 300°T @ 30 knots


Running Fix 2

Lay off second bearing taken at 1015





Running Fix 3

Lay off course and distance traveled to time of second bearing


Course 300°T @ 30 knots (7.5nm)



Running Fix 4

Move bearing 1 to end of course line and distance travelled - fix will be where two bearings cross




1015


Running Fix 5

Set and drift can be added to the course and distance vector, and the transferred bearing line run from that.




1015


Fixes and Cocked Hats


Compass Work


Compass Work

• Remember that the steering compass deviation table will only be accurate if:

1. No major alterations of structure or wiring have been made to the vessel;

2. No metallic objects (walkie talkies, knives, etc.) have been placed close to the compass;

3. Time - a vessels deviation can change over time.


Compass Work

• The variation on this compass rose 021°E (1988 13’W).

• What would the variation be today?


Compass Work

• What would be the deviation on a compass course of 315°C and a compass bearing of 000°C?

15.75 °E 2012


Compass Work• What would be the compass course to steer, if the

true course required was 200°T in 2012?

6°W


Compass Work

• Remember that the hand bearing compass will have different deviation from the vessels steering compass.

180°C


Radar Navigation


Radar Navigation

• The variable range marker (VRM) should be moved out until it just touches the object to be measured - that will be the range.


Radar Navigation

• When taking fixes using ranges taken at the same time, measure objects directly ahead or astern first, and measure objects closest to the beam last.

• This is different to visual bearings.


Radar Navigation

• Radar ranges off two objects should be as close to 90 degrees apart as possible, and with three objects about 60 degrees apart to obtain the greatest accuracy.

• Identify points off the chart, before obtaining radar ranges, NOT the other way around.

• Use two or more objects (points of land or small isolated islands) that can be positively identified, both on the chart and by the radar.


Radar Navigation

• Racons are receiver/transmitter (R/T) transponder devices that can be used as a navigation aid that shows on the radar screen.

• Racons and their identifying Morse mark are indicated on marine charts.

• Measure the range to the racon from the first dot or dash nearest your own vessel on the screen.


Radar Visibility

• Sight relies on light waves.

• Radar relies on electromagnetic waves.

• On our rescue vessels, the horizon for both is not far

Height of eye or radar

Distance to Visual Horizon

Distance to Radar Horizon

2 metres 3.0 nm 3.1 nm3 metres 3.6 nm 3.8 nm4 metres 4.2 nm 4.4 nm


Radar Visibility

• As such, care needs to be taken when measuring radar ranges over the radar horizon, unless the range being measured is a charted vertical face.


Detection Ranges


Detection Ranges for Low Antenna Heights

• Tankers, bulk carriers, cruise ships 9–12 nm Freighters, cargo ships, medium warships 6–9 nm Lightships 4–7 nm Trawlers, coasters, small warships 3–6 nm Metal-hulled boats 3–4 nm Wood, fiberglass boats with radar reflectors 2–4 nm Large sized buoys with reflector 3–5 nm Large sized buoys without reflector 2–3 nm Medium sized fairway buoys 1–2 nm

canadian coast guard auxiliary - pacific navigation and chartwork canadian coast guard auxiliary -...

Documents

nm slide

canadian hydrographic

good seamanship slide

knots course

chart symbols

drift course

t drift

drift fix