MARINA OIC-NW Theoretical Exam flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

Latitude and longitude

Latitude is angular distance north or south of the equator, 0 to 90 degrees. Longitude is angular distance east or west of the prime meridian, 0 to 180 degrees. One minute of latitude equals one nautical mile.

Speed distance time formula

Distance in nautical miles equals speed in knots multiplied by time in hours. Time equals distance divided by speed. Speed equals distance divided by time. The three-minute rule gives distance run as speed divided by twenty.

Running fix

A position fix obtained by advancing an earlier line of position by the course and distance steamed, then crossing it with a later line of position. Accuracy decreases with elapsed time and with set and drift.

Compass error CADET rule

Compass plus Deviation equals Magnetic. Magnetic plus Variation equals True. Reverse the sequence to convert from True to Compass. Deviation comes from the deviation card and variation from the chart.

Chart datum and soundings

Chart datum is normally Lowest Astronomical Tide. Charted soundings show depths below datum, and drying heights show heights above datum. Actual depth equals charted depth plus height of tide.

Overtaking rule

Under Rule 13 any vessel overtaking another must keep clear until finally past and clear, regardless of vessel type. Overtaking exists when approaching from more than 22.5 degrees abaft the other vessel's beam.

Crossing rule

Under Rule 15, when two power-driven vessels cross, the vessel that has the other on her own starboard side is the give-way vessel and must keep clear. The other vessel keeps course and speed.

Risk of collision

Under Rule 7, risk of collision is assumed if the compass bearing of an approaching vessel does not appreciably change. Do not assume no risk merely because a bearing change is observed at long range.

Restricted visibility conduct

Under Rule 19 no vessel has right of way in restricted visibility. Reduce speed to minimum steerageway when a vessel is detected forward of the beam, and alter course to starboard if possible.

Power-driven vessel lights

A power-driven vessel underway shows masthead light or lights, red sidelight on port, green sidelight on starboard, and a sternlight. Vessels of 50 metres or more show two masthead lights, the after one higher.

Buys Ballot's Law

In the Northern Hemisphere, with your back to the wind, low pressure lies to your left and high pressure to your right. The rule is reversed in the Southern Hemisphere.

Beaufort scale

The Beaufort scale relates wind speed to sea state. Force 6 is a strong breeze at 22 to 27 knots. Force 8 is a gale at 34 to 40 knots with moderately high waves and foam streaks.

Tropical revolving storm

A tropical cyclone forms over warm ocean water, typically above 26 to 27 degrees Celsius. It has a calm eye and circulates counter-clockwise in the Northern Hemisphere, generally moving westward then recurving poleward.

Advection fog

Advection fog forms when warm moist air moves over a colder surface, commonly over cold ocean currents. It differs from radiation fog, which forms over land on clear calm nights.

Swell

Swell consists of wind-generated waves that have propagated out of the generating area. It can arrive well ahead of a storm and indicates distant weather. Wave height depends on wind speed, fetch, and duration.

Metacentric height

Metacentric height equals KM minus KG. A positive value means initial stability. A larger value gives a stiff, fast roll; a smaller value gives a tender, slower, larger roll.

Free surface effect

Free surface effect reduces effective metacentric height. The free surface correction equals the sum of free surface moments divided by displacement. Keep tanks pressed or empty to limit the loss.

Turning circle terms

Advance is the distance ahead from the start of the turn to the point where the vessel is 90 degrees from the original course. Transfer is the sideways distance at 90 degrees. Tactical diameter is transfer at 180 degrees.

Squat

Squat is the vertical drop and trim change of a vessel moving through shallow water due to reduced under-keel clearance. It increases with speed and with the square of the Froude number.

OOW handover

Before taking over the watch, confirm the vessel's position, course, speed, traffic, weather, machinery status, and any standing orders. Never hand over without a proper briefing.

Bridge resource management

BRM uses closed-loop communication, challenge and response, and clearly delegated tasks. It manages complacency and fatigue and ensures the whole bridge team contributes to safe navigation.

Official log book

The official log book and deck log record courses, speeds, positions, weather, incidents, drills, and deviations. Entries must be factual, timely, and signed by the responsible officer.

Radar horizon formula

Radar range in nautical miles equals 1.23 multiplied by the square root of the sum of antenna height in feet and target height in feet. The radar horizon exceeds the visual horizon.

Radar resolution

Range resolution depends on pulse length, with a shorter pulse giving better resolution. Bearing resolution depends on horizontal beamwidth, with a narrower beam giving better bearing resolution.

ECDIS safety settings

ECDIS must display electronic navigational chart data, own position, and alarms. Set the safety contour and safety depth, verify the position source, and keep chart updates current.

AIS limitations

AIS transmits identity, position, course, speed, and heading, but it does not replace radar or visual lookout. AIS data can be absent, delayed, or erroneous, so use it only as an aid.

GMDSS sea areas

Sea Area A1 is VHF coverage with DSC, A2 is MF coverage with DSC, A3 is Inmarsat coverage, and A4 is outside A1 to A3. Distress alerts use VHF channel 70 or MF 2187.5 kHz.

MARPOL annexes

MARPOL Annexes cover oil, noxious liquid substances, harmful packaged substances, sewage, garbage, and air pollution. Oil Record Book entries are mandatory. Plastics are never discharged.

Fire triangle and classes

The fire triangle is fuel, heat, and oxygen. Fire classes are A for solids, B for flammable liquids, C for gases, D for metals, and E for electrical. Use the correct extinguishing agent for each class.

IMDG dangerous goods classes

IMDG classes are 1 explosives, 2 gases, 3 flammable liquids, 4 flammable solids, 5 oxidizers, 6 toxic and infectious, 7 radioactive, 8 corrosive, and 9 miscellaneous. Incompatible classes must be segregated.

Cargo liquefaction

Bulk concentrates can liquefy and shift if moisture exceeds the Transportable Moisture Limit. Check the TML, avoid overloading, and maintain adequate freeboard to reduce the risk of cargo shift.

Anchor scope

Anchor scope should be about five to seven times the depth in good holding ground, and more in poor holding ground or heavy weather. The anchor holds by its flukes digging in, not by weight alone.

Mooring lines

Spring lines prevent fore-and-aft movement, breast lines hold the vessel alongside, and head and stern lines control position. Watch the tide and adjust lines to avoid excessive strain.