Exam 1 Flashcards
What is a great circle?
Example
The largest possible circle that can be drawn around a sphere.
*Equator, Meridians
What are the two main chart projections and which one is used more?
Mercator (Most common)
*Great circles plot as curves
Gnomonic
*Great circle plot as a line
4 Types of chart scales
Smallest to Largest
1. Harbor
2. Coastal
3. General
4. Sailing
What is the Datum?
Specific Datum used
Datum info (Reference point) Always use same point
*Defines origin and orientation of the coordinate system on a chart
*WGS1984
Chart No.1
*Information on how to read charts, symbols, etc.
NAVDORM
*Policies, procedures, and organizational standards
*Navy instruction on navigating ships
Fleet guides
Info on US Navy ships
NOAA Coast Pilots
Updates on all US ports
USCG Light List
(US) Explain lights
List of Lights
(International) Explain lights
Local Notice to Mariners
Specific US regions
Sailing Directions
*Port information
*Foreign coastal waters
World Port Index
*All ports in the world that are frequently used
*Basic info, size, services
*Reference number to associate with Sailing Directions
NGA/USCG Notice to Mariners
*Weekly updates
*Kinda like a NOTAM
*For all Mariners
Types of tidal patterns
How many highs and lows for each?
*Semidiurnal tide: Twice a day, most normal
*Diurnal tide: Once a day
*Mixed tide: Could be anything
Ebb/Flood Current
*Ebb current: flow away from the shore (follows a high tide)
*Flood Current: flow towards the shore (follows a low tide)
OTSR
Optimum Track Ship Routing
5 Buoy types
Lateral
*What is safe is within the buoys
Isolated danger buoy
*Black and red
Safe water
*Red and white
*Any shape
*In open ocean/safe water when present
Special
*Prohibited areas
*Fishing traps, etc.
Information/regulatory
What does a preferred channel buoy mean?
Move in the direction of the top color
IALA A v IALA B
IALA B (Red Right Returning)
*Used by US, Japan, South Korea, & Philippines
IALA A (opposite)
* Used by everyone else
What reference plain for water depth/water height does the US use on our charts?
WGS1894
Types of Nav equipment
Radar: used for distance (range) only
Stadimeter: Used to determine precise ranges between ships in formation
Laser Range Finder: Used to determine ranges between ships or objects in close proximity
GPS: Used for nav, should not be only distance finder
Describe how radar detects other surrounding ships and how far away they are from you
Emits a Radio Wave that reflects off of all objects within its range. A computer system notes the angle at which the radio wave returns to find the bearing of the object. The same computer calculates the time between when the radio wave left the radar and when the radio wave returned and multiplies by the speed of light to determine range.
3 types of magnetism
How they differ
Terrestrial: Variation (Magnetic North)
Induced: Variation (steel in ship causes changes in magnetism)
Permanent: Ship gains extra magnetism when being repaired at port, loses most extra when underway, some if left which is permanent
Controllable Forces
*Lines
*Anchors
*Tugs
*Thrusters
*Engines
*Rudders
Semi-Controllable Forces
*Venturi effect
*Shallow water effects
*Squatting
*Bank effect
Uncontrollable Forces
Wind and Currents
How to determine a ship’s relative bearing to us
If a ship has a 090 relative bearing to us, it is directly off our starboard beam.
<–Port (ship) Starboard–>
LOPS, and what order to take them in
Lion of Position
3 LOPs are required to get a fix
1. LOP Beam
2. LOP Bow
3. LOP Stern
Fixes
Fic is the current location
*Visual fix (circle)
*Radar fix (triangle)
*Dead Reckoning/ DR (Half circle)
*EP (square)
6 Rules of dead reckoning
Polt a DOR
*Every hour on the hour
*Every course change
*Every speed change
*When obtaining a single line of position
*When obtaining a fix or a running fix
*Plot and label new course, speed, time, and DR out two fix intervals
Set and Drift
*Set: the direction of the current: typically expressed in “T”
*Drift: the speed of the water, expressed in knots
Advance and Transfer
When a ship begins a turn,
*Advance is how far forward the ship moves before reaching desired heading
*Transfer is how far horizontally a ship moves before reaching desired heading
