General Nav Flashcards
Symbols on Admiralty Charts
Chart 5011
International Regulations for Preventing Collision at Sea
MISC Pub 127
Three methods of calibrating a log
Dutchmans Log, GPS over measured 1nm, Dan Buoy
3 types of Nav Warnings
NAVAREA, Coastal, Local
Fetch
The long distance travelled by winds and waves over open water
4 Gyroscopic Laws
Gyroscopic Precision, Gyroscopic Inertia, Gravity, Earth’s Rotation
5 Gyro Errors
Lattitude, Ballistic, Speed, Rolling, Lock in
5 limitations of GPS
Spoofing, Over Reliance, Dilution Of Satelites, Human Error
3 Types of Speed Logs
DVL, Dutchamn’s Log, EM Log
3 Categories that effect radar detection
Material, Size, Shape
Unintentional Radar interference
Rain, Sea, Floating Objects
Luminous Range
The max distance at which it can be seen, determined only by its intensity and the prevailing visibility
Geographic Range
the max distance a light can reach an observer as determined by the height of the observer, the lights elevation and the curvature of the earth
Nominal Range
Is a lights luminous range for a meteorological visibility of 10 miles.
layers in the earth atmosphere
Troposphere, Stratosphere, mesophere, thermosphere, exosphere
Four processes for forming Clouds
lifting, expansion, cooling, condensation
Confined Waters
Any condition in which the navigation is constrained due to a decrease in available waters in relation to the proximity of land, dangers and navigational hazards
Restricted Manoeuvering
Any condition where the ships machinery or external factors such as tugs, navigational hazards or weather impede the ships manoeuvrability.
PDOP, HDOP, VDOP, TDOP, GDOP,
Position, Horizontal, Vertical, Time, Geometrical
AFTP 1
General Orders
AFTP 4
Fleet Training
AFTP 9
SUBSAR
Aus NAVAREA
NAV AREA 10 - 16 total
Laser Range bino limitations
Metal objects, magnetic field can cause errors, accuracy diminshed through bridge windows, not as effective in damp/wet weather
effective range approx 3nm
RADAR Definition
Radio Detection and Ranging
Transmitting Path
Transmitter, Duplexer, reciever, display
Reflective Properties
Material, Shape and Size
Super Refraction
Occurs when a visible light or radar wave is bent DOWN around the Earth’s surface in a duct.
= Increased horizon and detection ranges.
Experienced in:
- High latitudes (sea surface very low)
- Anticyclonic conditions, light winds and calm
- Trade Wind zones
- Coastal waters (warm air over a cool sea)
- Behind cold front of a depression
Sub-Refraction
Opposite to Super Refraction and occurs less frequently.
- Decreases normal detection range
- Temperature and humidity causes radar wave to bend UPWARDS instead of down.
- May be reduced to the point that contacts are visible by eye, but not displayed on radar.
Expected in:
- Cool air over a warmer sea (coastal waters – especially Polar regions IVO very cold land masses or ice fields)
- Warm moist air over the sea (increase in humidity with altitude may occur)
Attenuation
- Attenuation is the absorption and scattering of radar transmissions by rain and other forms of precipitation which may substantially affect radar performance. Rain, Ice, Hail and Snow may affect attenuation.
Confined Waters Examples
Berthing/Unberthing, Buoy Approach
wave length
the horizontal distance from a crest to the next succeeding crest of a wave, or between two corresponding points on successive waves
wave height
the vertical distance of a crest above the troughs on either side. This is the Crest-to-Trough height, not the height of the crest above the still water line
wave period
time which elapses between the passage of two successive wave Crests past a fixed point
Swell
waves that continue through their own momentum after the wind has stopped generating them
Period of encounter
the time which elapses between the passage of two successive wave Crests past a moving point
Sagging
convex bending of the hull usually due to greater buoancy fore and aft. Frequent when a vessel has full tanks
Hogging
Concave bending of the hull, usually due to greaterr buoyancy amidships.
Pooping
- Ship’s length is similar to wave length
- Ship’s speed is slower than wave speed
Wave may overtake the ship and break over its stern. Water will then sweep along upper decks at 1 ½ times wave speed, causing substantial damage
Broaching
- Ship’s length is similar to wave length
- Ship’s speed is similar to wave speed
Ship may ‘run’ for some time on crest of wave. Much more hazardous than being pooped.
Trigger Mechanisms
Convection, Turbulence, Orographic, Widespread Ascent (frontal)
5 factors affecting tides
Astronomical, Meteorological, Geographic, Resonance, Seismic waves
Four influences on tides
Declination and position of moon, of sun, latitude of the port, Natural resonance of the water
information on Echo Sounders
depth measured from, reporting units, standard report, date of last calibration, result of calibration
Possible Errors
Error depth calculation, operator read error, tranducer seperation error, false echoes, weak echoes
Calibrating echo sounder
Bar Check, Lead Line
Tropical Cyclone Formation Requirements
- An area of pre-existing low pressure
- Surface temp >26
- A min 5N/S
- Upper level divergence
- Little or no vertical wind shear
3 types of charts
Mercator, Gnomic projection, Transverse Mercator
Chart Reliability
Date of Survey, Survey Authourity, Type of survey, scale of chart, status of T’s and P’s, Topography, ZOC diagrams, completeness of coast lines
Nadir
The point on the celestial sphere vertically below the observer
apoggee/perigee
Moon and Earth
Aphelion/perihelion
Sun and Earth
