Navigation Flashcards
What does the direction of the line joining the plots from M1 to M2 represent?
The direction in which the maneuvering ship (M) is moving with respect to the reference ship (R).
What is relative motion?
The motion of one object with respect to another object
How is DRM expressed?
True bearing
What is relative speed?
The speed at which the maneuvering ship is moving in relation to the reference ship.
What is DRM?
This direction of the maneuvering ship (M) moves in relation to the reference ship (R)
What is relative distance?
The distance the maneuvering ship (M) moves with respect to the reference ship in a given period of time
What is SRM?
The speed at which the maneuvering ship moves in relation to the reference ship
What is LRM?
This line starts at M1 and extends through M1, M2 and M3
How do you establish a object’s location geographically?
Use one reference line running in a N-S direction and another line in an E-W direction.
What is projection?
The grid lines on a sphere are round and navigational charts are flat. The process in which grid lines are transferred from a round surface to a flat surface is projection.
What are the two types of projection?
Mercator and gnomonic
What kinds of charts are the most common?
Mercator projection charts
What are the parallels on a chart?
Parallels are the latitude lines. They run E-W and become farther apart as their distance from the equator increases.
What are the meridians?
Meridians run N-S and are the longitude lines. They are parallel and equally distant from one another
What is 1 minute of latitude?
1 nautical mile
What is gnomonic projection?
Gnomonic projection preserves the curvature of the meridians and parallels.
What are polar charts normally in?
Gnomonic projections
What is each degree divided into?
60’ (minutes) or 3600” (seconds)
What is the reference line for all meridians?
Prime meridian
How many meridians does the charting grid have?
360 meridians
What is the reference for the parallels?
Equator
What is the latitude of a point?
The points angular distance in degrees, minutes, seconds of arc north or south of the equator, measured along the meridian that runs through the point.
What is 1’ (minute)?
It is 60 seconds.
Why do you use the latitude scale and not the longitude scale for measuring distance?
The parallels are always equidistant from each other, whereas meridians converge on the poles.
What is the scale of a chart?
The scale indicates the relationship between the size of a feature on the chart and the actual size of the feature on the Earth’s surface.
How does a chart’s scale appear?
One of two ways; ratio or fraction
What does a small scale chart cover?
A large area
What does a large scale chart cover?
A small area
What scale does a harbor chart have?
Scales larger than 1:50,000. Harbor charts are used in harbors, anchorage areas and smaller waterways.
What is the scale for coastal charts?
1:50,000 - 1:150,000 Coastal charts are for coastal navigation, outside reefs and shoals when the vessel is in sight of land or aids to navigation.
What is the scale for sailing charts?
1:600,000 or smaller and are used in fixing a ship’s position as it approaches the coast from open ocean
How are soundings given on a chart?
Depths are given in feet, fathom and meters.
What does Fl 10sec 55ft 12M HORN mean?
Flashing every 10 seconds (one full on-off cycle)
55ft above the mean high water
Light is visible for 12 miles on a clear, dark night
Sounds a horn
What are the four standard colors for lights?
Red, green, yellow, white
If there is no R, Y, G symbol on the chart, what does that mean?
The light is assumed to be white.
What is the chart symbol for a buoy?
Diamond shape
A small dot is near every buoy symbol. What does it mean?
That is the buoy’s approximate location.
If the dot next to a buoy symbol is enclosed in red, what does that mean?
The buoy is lighted.
Three types of coordinates may be used to locate any given position.
Geographical, polar or grid.
What are the grid systems?
They are used to simplify exchanges of positional information among ships, aircraft and shore activities.
What 3 types of grids are used?
Cartesian coordinates
GEOREF system (world geographic reference)
Universal Transverse Mercator grid (UTM)
What is the Cartesian coordinate grid system used for?
Position reporting in large-scale naval operations
What is the GEOREF system used for?
Worldwide reporting system and used for exchanging position information
What is UTM for?
This grid is used to increase reporting accuracy in localized military operations.
What is DLRP?
Data link reference point, where the OTC establishes the center of the grid
The Cartesian coordinate grid system has four quadrants. What are they?
Red = Northwest White = Northeast Blue = Southeast Green = Southwest
Grid positions are indicated by color and then followed by six numbers. What does this mean? RED 060 100
Northwest quadrant
060 = X coordinate (east or west)
100 = Y coordinate (north or south)
How is a transverse Mercator projection made?
The same way as a Mercator projection, except that the transverse projection is rotated 90 degrees.
What must a vessel apply to offset the effects of wind and current?
Course and speed corrections
What is set?
The direction toward which the forces tend to push a vessel
What is drift?
The velocity of the force in knots
How does the navigator determine set and drift?
By checking various publications, tide tables and current tables to predict the amount of set and drift the ship will experience while entering port.
What must a navigational plotter be familiar with?
- Reading and interpreting chart symbols
- Correct navigational procedures
- Computing set and drift
- Dead reckoning own course and speed made good
- Determining compensating and correcting courses and speeds.
While the ship is within radar range of land, CIC is required to keep a coastal navigation plot on a chart by plotting radar fixes. What information must the plot display?
- The intended track, marked with reference points
- Radar fixes every 30 minutes
- Operational boundaries
- Set and drift of the current
- Wind direction and velocity
- Positions of any hazards to navigation
- Locations of any objects of potential interest.
What do you do when you obtain an unreliable fix in CIC?
Plot it as an EP and attempt to obtain a more accurate fix ASAP.
If a ship enters a harbor during reduced visibility, who has the responsibility for safe piloting?
CIC
If CIC cannot plot a fix during reduced visibility within 2 minutes of plotting an EP, what must they do?
Recommend all stop until it can determine an accurate position for own ship.
What are anchorage charts?
They are harbor charts with anchorage berths overprinted in colored circles of various diameters.
What are lines of anchorage?
Series of berths of the same size laid out in straight lines
What does each anchorage (berth) designated by?
A number, a letter or a combination of both printed inside the circle.
When a ship is ordered to anchor in a specific berth, what must CIC personnel do?
- From the center of the berth, draw the letting-go semicircle.
- From the center of the berth, lay off the intended track, using the appropriate approach courses and navigational aids for determining ship’s position.
- Determine the distance from the hawespipe of the ship to the radar antenna.
- Draw the range semi-circles. Draw arcs every 100 yards out 1,000 yards and then arcs at 1200, 1500 and 2000 yards.
- From the center of the berth draw the bearing lines at 5 degrees and 10 degrees in the direction of your approach and label the lines using reciprocal bearings.
What are the International Rules?
They are the specific rules for all vessels sailing on the high seas and in connecting water navigable by seagoing vessels.
Who do Inland Rules apply to?
All vessels sailing on inland water of the U.S and to vessels of the U.S on the Canadian waters of the Great Lakes to the extent that there is no conflict with Canadian Law.
The International Rules were formalized at the convention on the International Regulations for Preventing Collisions at Sea, 1972. What are these rules known as?
72 COLREGS
The International and Inland rules contain how many rules?
38 rules that compose the main body of the rules and five annexes which are the regulations.
What parts are the International and Inland rules divided into?
Part A - General Part B - Steering and Sailing Rules Part C - Lights and Shapes Part D - Sound and light signals Part E - Exemptions
What are the demarcation lines?
Lines delineating waters upon which mariners must comply with the 72 COLREGS and waters upon which mariners must comply with the Inland Navigation Rules
How long does a short blast last?
1 second
How long does a prolonged blast last?
4-6 seconds
What weekly NGA publication contains all corrections for nautical charts and publications?
Notice to Mariners
What elements make up a ship’s tactical data?
- Acceleration
- Deceleration
- Acceleration/deceleration distance,
- Advance
- Transfer
- Tactical diameter
- Final diameter
- Standard rudder
What member of the navigation team gives timely warning to the conning officer concerning all dangers to navigation?
The piloting officer
When taking a Celestial fix what shape should you use on a chart?
A circle with a dot in the center
What does RADAR mean?
Radio Detection and Ranging
What shape should be used on a chart to indicate a radar fix?
Triangle
What symbol is used for an EP?
Square with a dot
What is an EP?
Estimated position - is the most probable position of a vessel. Determined from data of questionable accuracy, such as applying estimated current and wind corrections to a DR position
What is a fix symbolized by a circle?
An accurate position determined without reference to any previous position. Established by visual or celestial observations
What is a fix symbolized by a triangle?
A relatively accurate position determined by electronic means without reference to any former position.
