Radar
Explain the principles of how a radar works?
Works by sending out pulse
Pulse bounces of targets and returns to vessel
Measures the amount of returning energy
Works by line of sight
What is an S Band radar?
10cm & 3Ghz
Useful for long range detection
Less affected by rain / sea clutter
Requires more adjustment
Requires high sea clutter settings to clear screen
Promulgation errors at long range
More affected by atmospherics
In terms of collision regulations, what advantages does radar give you?
Rule 5 – Look out by all available means
Rule 6 – Helps determine safe speed
Rule 7 – determining the risk of collision
Rule 8 – Action to avoid collision
Rule 19 – Detects by radar alone the presence of another in restricted visibility
Annex I – detects a SARTS and radar reflectors carried by lifeboats and liferafts
Provides relative approach of targets
Target management in high traffic density
What are the limitations of ARPA?
Requires minimum 3 minutes to provide accurate data
Target swap may occur when targets to close together
Inaccurate inputs such as heading and speed
Detection of small targets at an adequate range
Use of clutter controls
Sources of interference and weather
What is the normal Radar set up for collision avoidance?
Course up
Relative trails = early warning for targets
Sea stabilised = own vessel and other vessel influenced the same by tide
How quick should a steering gear turn?
At maximum ahead service speed the rudder must be capable of
- Main:From 35° on one side to 35° on the other in not more than 28secs
- Auxilliary from 15° on one side to 15° on the other side in not more than 60 seconds at one half of the maximum ahead service speed or 7 knots, whichever is the greater.
When should the vessel be in manual control?
Gyro failure
During pilotage
Once per watch -> change over test
Congested traffic
Restricted visibility
What checks would you make when handing over the deck watch?
Depth of water at the berth
Vessel’s draught
High and low water
Mooring arrangement
State of engines
Work to be performed
Nature, amount, cargo operations,
Signals or lights exhibited or sounded
Number of crew on board, minimum amount and shore leave
State of fire fighting equipment
Special port regulations
Gangway watch arrangement
Master’s standing orders
Communication with shoreside
What are the requirements for performing a deck watch?
OOW shall;
Make rounds to inspect vessel at appropriate intervals
Condition of gangway and security arrangement
Mooring / anchoring arrangement
Draught, under keel clearance, heel and trim is within limits
Weather and sea state
Observance of regulations concerning fire and safety
All persons on board
Enclosed space entries
Exhibition and sounding of signals
Receipt of storm warning / strong winds, take appropriate measures to protect vessel, crew, cargo and environment
Measures to prevent pollution
Enter appropriate log book entries
In event of emergency raise the alarm
What is the role of the Pilot?
Advisor to Master on approach to port
Part of the bridge team
Why is a radar useful?
Detects the presence of targets in all visibility - except very heavy rain / snow / sandstorms
Identifies targets relative line of approach
CPA / TCPA
Can detect distress signal - SART
Capability for chart overlay
Display AIS info
What is the procedure for starting a radar?
- Check antennas clear from ropes, halyards or men working at height
- Check no permits to work in force
- Turn on the power
- Transmit
- Tune
- Brilliance - brightness
- Gain – power of transmission signal
- Need slightly speckled background
- Tune
- Tune to correct frequency
- Or use auto tune.
In terms of collision regulations, what disadvantages does radar give you?
Can lead to over reliance on electronic equipment
Requires 3 minutes to produce accurate data
Distracted by radar and not maintaining a look out by using eyes.
Must not rely on scanty radar information
May give false sense of safety and proceed at higher speed
Why are accurate inputs important for ARPA?
Inaccurate heading or speed inputs produce wrong OWA triangles.
Leads to wrong aspect / target heading and speed
But OA line remains accurate therefore so does TCPA / CPA
No gyro input results in un-stablised heading – unable to track targets
No speed input results in bad aspect
What factors affect the range scale of a radar in use?
Need overview of upcoming traffic
Number of radars – two allows long and short range
Vessel speed
Visibility
Navigational hazards – port approaches
On passage – long range needed for early warning
What is restricted visibility?
Restricted visibility means any condition in which visibility is reduced by fog, mist, falling snow, heavy rain-storms, sand storms or any other similar causes.
What is an X band radar?
3cm radar, 9Ghz,
Good definition of small targets
Detects SART (hence why required by SOLAS)
Liable to interference from rain
Why are ranges more accurate than bearings?
Beam has height and width
Flat beam may miss target
Therefore, give height and width over a few degrees to avoid missing targets
Return gives the leading edge of a target
What can over adjustment of clutter controls do to the radar?
Make screen empty of all returns (hence having slightly speckled background)
Miss small targets including vessels and buoys
Reduce leading edge of large targets
What is a slotted wave guide?
- Located at the front of the radar and concentrates the energy into a beam
What is the normal navigation set up for Radar?
North up – same as chart / ECDIS so easier to spot conspicuous objects
Ground stabilised
Fixed Targets with true trails = O
Relative vector is not affected by stabilisation
What are the deck pre-departure checks?
Cargo operations complete
Ballasting operations complete
Final drafts taken, fwd, aft and midships
Dock water density taken
All crew on board & ETD posted
Cargo gear housed and secured
Ship secured and ready to proceed to sea
Hatches battened down
watertight doors secured
Heavy and movable objects secured
Gangway and/ or accommodation ladder secured
If heavy weather us expected have appropriate measures been taken?
Winches checked
Anchors cleared away
Windlass checked
Stowaway search carried out
Crew check carried out
What are the bridge pre-arrival checks?
Has Master Pilot exchange information been prepared?
Has the passage plan been updated?
Has the ETA been sent with all relevant information?
Has the port been informed of special berthing requirements?
Has the engine room been informed 1 hour prior arrival at Pilot station?
Has the bosun and sailors been informed
ECDIS checked and verified
VHF on appropriate channels
Has the steering gear been tested?
Mooring winches and ropes checked and prepared
Anchors been cleared away?
Have local flags been hoisted
What checks would you make when navigating in restricted visibility?
Ensure the following equipment is operational
Radar / ARPA
VHF
Fog signalling apparatus
Navigation Lights
Echo sounder, if in shallow waters
Watertight doors closed
Have look outs been posted
Has the Master and Engine room been informed?
Are COLREG’s complied with, particularly Rule 19?
Is the vessel ready to reduce speed, stop or alter course quickly?
What information can the Pilot provide the Master?
Up to date information
Changes to Nav Aids
VHF channels
Traffic situations
Liaising with locals
Passing through lock procedures
Navigation Equipment
What is the principle of a Sextant?
When a ray of light is reflected twice in the same plane by two plane mirrors, the angle between the first and last directions of the ray is twice the angle between the mirrors.
What is index error?
Mirrors are not parallel with each when at 0°
Hold instrument upright
If there is a step in the horizon then adjust screw nearest instrument.
What can you use a sextant for?
Position fixing from sun, planets and stars
-Sun run sun
-Merpass
-Star fixes
Vertical sextant angle
-Measuring distances from land / dangers
Horizontal sextant angle
-Can also be used for finding compass error.
What is merpass?
- When the sun passes over the observes meridian
What is merpass?
- When the sun passes over the observes meridian
What is perpendicular error?
Index mirror not at 090° to plane of instrument
Hold instrument horizontally
Index arm at 50° - 60°
True and reflected image of graduation arc.
What happens if you are unable to correct the errors from a sextant?
Nearly all errors are correctable
Unit may have some errors already – check card that came with unit.
Adjust micrometer wheel - remember to apply offset to any calculation
What happens if you are unable to correct the errors from a sextant?
Nearly all errors are correctable
Unit may have some errors already – check card that came with unit.
Adjust micrometer wheel - remember to apply offset to any calculation
What is side error?
Horizon mirror not perpendicular to the plan of the instrument.
Hold instrument at 70° with index bar at 0°
Observe the horizon – 2 images should be in line
Adjust with the outer screw
What is side error?
Horizon mirror not perpendicular to the plan of the instrument.
Hold instrument at 70° with index bar at 0°
Observe the horizon – 2 images should be in line
Adjust with the outer screw
what are the uncorrectable errors of sextant?
Uncorrectable errors are found during commissioning and testing of equipment.
Collimation – telescope not parallel
Graduation – marks not accurate
Worm & Rack – mechanism that moves index bar over arc as micrometer turned. May become loose over time
Shade error – imperfections with shades and not parallel
Prismatic -Either index or horizon mirrors, side of mirror not parallel therefore causing bending of light