General Bridge / Nav

Question 1

**What is variation?

&

What is Deviation?**

Answer 1

Variation:

• The angular difference between true and Magentic North
• Geographical Location - Nothing to do with the vessel itself

Deviation:

• The differerence between Magentic North and Ships Compass North for a given ships heading
• Calcuation is only on the course steered and nothing to do with the bear of an object

Question 2

What Causes Deviation?

Answer 2

Hard Iron - Permanent Magentism

• Ships construction
• Corrected by athwartship and horizontal magents fore and aft and also vertical magenets, healing bucket

Soft Iron - Induced Magentism

• Ships instructments, electro magnetic equipment, Cargo
• Correced by Flinders Bar and Kevlins Balls, which are made of Soft Iron. They get induced with an equal and opposite effects of what is happening to the Magnetic compass and corrects it.

Question 3

How often should a magnetic compass be swung or checked?

Answer 3

• After being laid up after a long period of time i.e. dry dock
• On installation
• Any major trauma to the ship - Fire, Collision or Grounding
• Or if the Deviation card is inaccurate
• Period not exceeding two years

Question 4

Magnetic Compass Information

Answer 4

• SOLAS requires you to keep a fully corrected magnetic compass. It doesn’t say how often it should be corrected though
• Compass Error book that shows that the deviation card is correct, means that it need not be swung or adjusted
• In Heavy seas / hitting bigs waves, if the MC is not accurate any more - Likely cause is that the magnets have been dislodged. On the reverse side of the deviation card should be the location of the magenets. Compass should then be corrected at the next available opportunity.
• If wake is not in a straight line when steering on autopilot, Could be caused by a wondering gyro. Change autopilot to steering by magentic compass and correct for variation / deviation. Service Gyro and next available opportunity. ( A wondering gyro will see the heading move and then come back as the unit attempts to correct itself. Usually casused by bearings wearing out) Average Gyro life is 5 years.

Question 5

Define Nominal Range, Geographical Range, Luminous Range

Answer 5

Nominal Range = The range of visibilty in 10nm

Geographical Range = The physical range at which you can see an object due to the height of the object and your height of eye

Luminous Range = The power of the light

Question 6

Where can you find details of:

Lights?

Reporting Points?

Chart symbols?

Answer 6

Admiralty List of Lights:

• Go into the back of the book and look up the name
• It will give you a number
• Go into the front of the book with the number
• Details will be great than what can be printed on the chart
• Greater detail of lights can also be found in Sailing Directions

Reporting Points:

• Details can be found in the Pilot Book ALRS Vol 6.
• *Chart Symbols:** NP5011 (Chart 5011)
• *ECDIS Symbols and Abbreviations:** NP5012

Question 7

Define:

Source Data
CATZOG
ECDIS Layers

Answer 7

Source Data:

• Who did the survey, when and how + accuracy
• What the realiabily is (through * in triangles)

CATZOG:

• Category zone of confidence - reliability of the source data - position accuracy, depth accuracy and sea floor coverage
• On an ENC you need to go into custom settings and turn the layer on. Do this when passage planning
• A1, A2, B, C, D, U - 6 stars - no stars. A1 =0.5m depth / 5m position accuracy / full search area

ECDIS Layers:

• BASE
• STANDARD
• CUSTOM / ALL OTHER

Question 8

Chart Corrections

Answer 8

-You can only correct a chart that is the latest edition
-All latest edition charts get corrected from earliest date to present date
-On a weekly basis you download the Weekly Notice to Mariners. If we can’t download it we will get it sent to us.
-All BA Charts from January 2015 have a QR reader code on them. PSC likes to check them -ensures authentic, checks latest edition + NM’s
-Cumulative list of NtM - every 6 months
-AS of NTM - Yearly - All Ts and Ps in force

Question 9

What are the 8 Parts to the Weekly Notice to Mariners?

Answer 9

1. Notes on how to correct Admiralty Publications - New Publications published that week
2. Chart Corrections - Pg1 is chart affected by this weekly edition. Also includes T’s & P’s
3. Reprints of NAVAREA 1 Navigational Warnings
4. Updates to Sailing Directions
5. Updates to Admiralty List of Lights and Fog Signals
6. Updates to Admiralty List of Radio Signals
7. Updates to Miscellaneous Admiratly Publications
8. Updates to Admiralty Digital Products and Services

Question 10

What are temporary and Preliminary Notices (T’s & P’s)?

Answer 10

T = Temporary:

• i.e. A buoy is removed for maintenance and there is no replacement, as it’s near a danger they put a temporary south cardinal telling you to keep south. Once the maintenance is complete and the original buoy is back in place the Temporary Notice is withdrawn

P= Preliminary:

• is a warning that something is going to change. i.e we are going to replace a cardinal mark with an isolated danger at some point in October. Exact date unknown. Once completed it will be issued as a permanent correction

On an annual basis the UKHO issue an Annual Summary Notice to Marines - Reprints of all T’s and P’s current in force from previous years.

Question 11

What is a Mercator chart?

Answer 11

In a Mercator projection:

• Meridians of longitude are parallel.
• Line of latitude, while still parallel are no long equidistant by further apart the further north or south from the equator. This casues distortion in the shape and size of land and ocean masses as these features are enlarged closer to the poles
• The advantage of Mercator chart is that meridians and parallels cross each other at right angles to form a rectangular grid. This means a straight line course through the water can be plotted as a a straight line on the chart. Something that is not possible on other projections
• Transvere Mercator Chart: Is when the cylinder is turned through 90* degrees. Advantages for countries like Chile, which has a long North / South border but a narrow East / West.

Question 12

What is a Gnomonic Chart?

Answer 12

• Meridians converge and lines of latitude are curved. It’s like unfolding a Terry’s Chocolate Orange
• For a Gnomonic Projection, imagine placing a screen tangential to the Earths surface and then project the features onto it (done mathematically) This projection can be used in polar regions where a conventional Mercator projection would not work, it is also used for large scale harbour plans and charts for planning ocean crossings.
• Great circle routes are straight lines and rhumb lines are curved.
• A great circle is the longest line that can be drawn around the earth A segement of a great circle is the shortest distance between two points on the earths surface
• When planning ocean passages, small scale gnomonic charts can be used to calculate great circle routes. On longer passages, ships can save fuel by sailing the shorter great circle route.

Question 13

Traffic Separation Schemes

Answer 13

1. When printed on a chart it is important to know if it is adopted by the IMO - If not, Rule 10 does not apply! However any TSS not adopted by the IMO can still be made to comply with Rule 10 of Colregs. This is done by Rule 1 - Colregs. They make a special rule. If as special rule is in place, it will be noted on the chart in magenta.
2. UKHO will tell us if its not adopted, but will tell us where to get the information if it is adopted:
   - Sailing Directions
   - Annual Summary Notice to Mariners (Old Charts)
   - Mariners Handbook can provide guidance on TSS adoption
3. When Passage Planning, all notes on the chart in magenta should be read prior.

Question 14

What is the annual summary notice to Mariners?

Answer 14

Divided into two parts: NP247(1) & NP247(2)

1. A publication issued by admiralty (UKHO) on yearly basis.
2. The notices advise mariners on the important matters related to ships navigation, hydrographic information, aids to navigation and changes in shipping channels.
3. The current edition supersedes and cancels the previous one
4. This annual summary is of prime importance to mariners in keeping navigational chart folios up to date for corrections pertaining to temporary and preliminary notices for ships navigation and sailing directions
5. The annual summary serves as a database with details of history of corrections for all the charts and sailing directions published by the British Admiralty or UKHO.

Question 15

What are the contents of NP247(1)?

Answer 15

Section 1 - Annual Notices to Mariners section 1 - 26

Section 2 - Temporary and Preliminary Notices

• The publication also includes an exhaustive list of traffic separtion schemes and information related to ship routing system shown on admiralty charts
• It contains port state notification issued under the EU Directives and some parts of ship navigation related regulations issued by the United States. The annex provided with the notice contains extracts from the US navigation safety rules.

Question 16

ALRS Volumes
Volume 1 (NP281)
Maritime Radio Stations (Parts 1 & 2)

Answer 16

Split across two publication, Volume 1 includes radio details for:

• Global Maritime Communications
• Satellite Communication Services
• Coastguard Communications
• Maritime Tele-Medical ASsistance Service (TMAS)
• Radio Quarantine and Pollution reports
• Anti - Piracy Contact Table

Question 17

ALRS Volumes
Volume 2 (NP282)
Radio Aids to Navigation
Different GPS (DGPS)
Legal Time
Radio Time Signals
Electronic Position Fixing System

Answer 17

• Listing of VHF Radio Direction-Finding Stations
• Radar Beacons (Racons and Ramarks)
• Known operational Automatic Identification Systems (AIS)
• Aid to Nagivation (A-to-N)
• Radio Beacons transmitting DGPS corrections
• International Standard and Daylight Saving Times and Dates
• International Radio Time Signal Broadcast Details

Question 18

ALRS Volumes
Volume 3 (NP283)
Maritime Safety Information Services (Parts 1 & 2)

Answer 18

• Maritime Weather Services
• Safety Information broadcasts
• Worldwide NAVTEX and SafetyNET information
• Submarine and Gunnery Warning details (Subfacts and Gunfacts)
• Radio-Facsimile Stations, frequencies and weasther map areas

Question 19

ALRS Volumes
Volume 4 (NP284)
Meteorological Observation Stations

Answer 19

• All Met Observation Station listed worldwide

Question 20

ALRS Volumes
Volume 5 (NP285)
Global Maritime Distress and Safety System (GMDSS)

Answer 20

• Worldwide communication requirements for distress, search and rescue
• Extracts from SOLAS and ITU Regulations
• Distress and SAR (incorporating MRCC and MRSC contacts)
• Worldwide NAVTEX and Maritime Safety Information

Question 21

ALRS Volumes
Volume 6 (NP286)
Pilot Services
Vessel Traffic Services
Port Operations
(Parts 1-8)

Answer 21

• Detailed Pilot Information, contact details and procedures
• Vessel Traffic Service informtaion, contact details and procedures
• National and International Ship Reporting Systems
• Port Information, contact detail and procedures

Question 22

Position Fixing Interval

Answer 22

The frequency of fixing should depend on the distance from navigational hazards and the time the ship would take to run into danger before the fix. Should be at least half the time before running into danger.

Question 23

Monitor GPS accuracy

Answer 23

• Verify number of satellites
• Check DOP values, lower is better -best below 5
• RAIM - Receiver autonomous integrity monitoring
• Cross-reference with other nav. methods (3-point fix, depth)
• Observe sudden accuracy changes
• Use GPS with SBAS support
• Keep GPS up to date (Hardware and Software)
• Understand the GPS limitations

Question 24

Safety Depth vs Safety Contour

Answer 24

Safety Depth = Draught + Squat + UKC (your safety margin/company policy) -HoT

Squat = Cb x V2/100 (Open Water)
Squat = Cb x V2/50 (Confined waters)

Darkens any Soundings / makes them more apparent - set by the navigator. If contour not available the ECDIS will use the next deepest contour

Safety Contour demarks the boundary between safe water and shallow water with an extra wide isoline. Used to give an alarm - set to 30m by ECDIS if not set.

UKC:
* Vessel healing
* Reliability of charted depth data (CATZOCs)
* Reliability of echo sounder
* Tidal Levels
* Ability to fix position
* Mano. of own vessel
* Areas of mobile bottom

Question 25

Distance off danger - coastal navigation

Answer 25

Not possible to lay down hard and fast rules. Depends on: -Draught of the ship relative to the depth of water -Weather conditions / wind / fog -Direction and rate of current and tidal stream -Volume of traffic -Age and reliability of survey information on the chart -Availability of safe water 1.5 - 2NM is advised - close enough to perform suitable terrestrial position fixes. If danger is on Starboard allow room for collision avoidance.

Question 26

Parts of a magnetic compass

Answer 26

Question 27

Rhumb line vs Great Circle

Answer 27

Great circle is a plane on sphere, which passing through its centre cuts it into two equal parts - and is the largest possible circle that can be drawn around a sphere. The shortest distance between two points on a sphere is the arc of the great circle that contains both points. Cuts each meridian at different angle Rhumb line route cuts all meridians at same angle

Question 28

Variation on ECDIS

Answer 28

-Interrogate the cell - purple arrow (pick site for variation at that position) / crosscheck against the variation on GPS unit -Uses the World Magnetic Model, updated every 5 years