Navigation Flashcards
When speaking of degrees in giving course or heading, always use
three digits
Directions on the charts are in both
true degrees and magnetic degrees
True direction uses the ______ ______ ____ as a reference point.
geographic North Pole
Magnetic direction uses the ____ ____ ___ as the reference point
Magnetic north pole
The difference between the true and magnetic direction is called
variation
Directions steered on the compass are either
true degrees or magnetic degrees
The direction of vessel, land mass or landmark in a 360 degree circle in reference to the vessel’s bow are
relative bearings whereas true and magnetic use true or magnetic north as the reference. For example 000 degrees if “dead ahead” and 090 degrees if off the starboard beam, 180 degrees is directly astern and 270 degrees if off the port beam
The sum of there errors ( variation and deviation) that precent a magnetic compass from reading true north are called
compass error
Variation varies according to
geographic location
The variation for any geographic location can be dound
near the center of the compass rose nearest to the area of operation on the nautical chart of the area
Increases in variation may continue for many years, sometimes reaching large values, and then
decrease again
Determine the mouth of variation
Find the compass rose nearest to your location
Locate the variation and annual increase/decrease from the compass rose and the year observed
Subtract the year indicated in the compass rose from the present year
Multiply the number of years difference by the annual increase or decrease and round to the nearest whole degree
Add or subtract the amount of change to the variation printed in the compass rose
The magnetic compass error caused by magnetic influences on the vessel is call
deviation
Sources of compass deviation include
Metal objects around the compass
electrical motors and electronic equiment
The vessel itself
Deviation is measured in
degrees and will be either east or west of what the actual magnetic heading should be
The amount of deviation is determined by
swinging ship
on board a ship, the deviation is recorded on a
deviation table and posted near the compass
The deviation table lists deviation for every
15 degrees of the compass
Deviation can also be determined by
running a range, which is a line of bearing made by any two fixed landmarks on a nautical chart. Coast Guard navigation ranges which typically mark the center of a channel are excellent for this purpose
And aid to navigations is
any device external to a vessel or aircraft intended to assist a navigator to ermine position or safe course or to warn of dangers or obstructions to navigations
On seacoasts, lateral aids conform to the
conventional direction of buoy age, which is clockwise direction around the coastline from north to south on the Atlantic coast and south ton other and then west in the Gulf of Mexico and south ton other on the Pacific Coast
Lateral aides found at junctions of navigable channels and often mark wrecks or obstructions
Preferred Channel Marks
____ _____ ____ band indicates the side of the preferred channel on Preferred Channels Marks usually the “main” channels when entering from seaward.
The top color
If a Preferred Channel Mark is lighted, the light color will be
the same as the color of the top band.
Preferred channel buoys may be _____ but not _____.
Letters but not numbered
These aid are used to mark fairways, mid-channels, and offshore approach point and have unobstructed water on all side. They can also be used by a vessels operator transiting offshore waters to identify the proximity of intended landfall.
Safe Water Marks
Safe water marks may have a _____ topmark
red
These aids indicate an isolated danger which may be passed on all sides
Isolated Danger Marks. They are erected on or moored on or near diners and should not be approached closely without special caution.
This aide is a Pair of aids to nivation which when lined up Wirth eat other, mark a channel center line.
Ranges or Range Loghts
Special Marks (Yellow) are not intended to assist in navigation, but rather to alert the mariner to a special feature or area such as
Spoil areas
Pipelines
Traffic Separation Schemes
Jetties
Which marks have orange geometric shapes agains a white backgrou
Information and regulatory marks.
The meaning associate with the orange shapes are
Open-face diamond signifies danger
vertical diamond shape having a cross center within indicates vessel are excluded
circular shapes indicated that certain operating restrictions are in effec
A watch circle is defined by
mooring lengths and buoys can be expected to move within this circle. Actual watch circles do not coincide with the symbols representing them on charts.
Mariners should never rely on
buoys alone to determine positition
aids to navigation which are permanently fixed to the earth’s surface are
Beacons
Beacons include
large lighthouses to small single-pile structures and may be located on land or in the water.
Lighted beacons are called
lights
unlighted beacons are called
daybeacons
beacons exhibit a
day marks. These are color geometric shapes which make an aid to navigation readily visible and identifiable agains background conditions
a lighthouse’s day make can be
the structure itself.
These daymares have no ____ significance
lateral
What has a considerable effect on the distance which lights can be seen
The condition of the atmosphere including fog, have, dust, smoke or precipitation
What can cause a light to be seen further away than under ordinary circumstances
Atmospheric refraction
The glow os a powerful light is called
loom
What can reduce the distance at which buoy lights are detected
buoy motion
What in general, are used to make shoals or to warn the mariner of other obstructions to navigator or of nearby land
red sectors
Only aids with lateral significance have
green or red lights
___ lights on aid to navigation mark ports sides of channels and locations of wreck or obstructions that must be passed by keeping these lighted aids to navigation on the port hand of a vessl
Green lights
What colored lights are used on aids to navigation marking starboard side of channels and locations of wrecks or obstructions that must be passed by keeping these lighted aids to navigation on the starboard and os a vessel. The same color lights are also used on preferred channel maps where the the preferred channel is to port
Red lights
Dhow are light rhythms laterally significant
they aren’t
Red or green flashing lights less than 30 flashes per might will
make the side of a channel
A yellow flashing light indicates
a special mark
Preferred channel marks exhibit a
composite grou-flashing (2+1) light rhythm of two flashes followed by a single flash
Safe water mark lights she a
white Morse code “A” rhythm (a short flash followed by a long flash)
Safe water marks are used to mark
fairways, mid-channels and offshore approach points and have unobstructed water on all sides.
Isolated danger mark lights show
a white flashing (2) rhythm (two flashes repeated regularly)
A quick flashing light flashes
more than 60 flashes per minute
A quick flashing light indicates
a distinct cautionary significance such as sharp turns, sudden channel constrictions, wrecks or obstructions
All solid red and solid greenaids to navigation are
numbers
red aids to navigation have
even numbers
green aids to navigation have
odd numbers
the numbers on solid red and solid green aids to navigation increase from
seaward, proceeding in the conventional direction of buoyage
Letters will increase in alphabetical order from seaward,
proceeding in the conventional direction of buoy age and are added to numbers as suffixes
Preferred channel, safe water, isolated danger, special marks, and information and regulatory aids to navigation may be but not numbered.
lettered, but number numbreed
Which buoys and dashboard shapes mark the left side of a channel when proceeding from seaward and are associate with solid green or green and red-banded marks where the top-most band is green
cylindrical buoys (can buoys) and square dayboards
mark the ___ buoys and ____ dayboards mark right side of the channel when proceeding from seaward. These aids to navigation are associated with solid red or red and green-banded marks where the topmost band is red.
Conical buoys (nun buoys) and triangular dashboards
The Intarcoastal Waterway (ICW) runs parallel to the Atlantic and Gulf coasts from New Jersey to the Mexican border. Aids to navigation marking the ICW display
unique yellow symbols to distinguish them from aids marking other waters. When following the conventional direction of buoyage, yellow triangles indicate aids that should be kept to starboard (right), and those with yellow squares should be kept to port (left).A yellow reflective horizontal strip on a dayboard indicates the aid to navigation marks the Intracoastal Waterway, but it has no lateral significance.
Lights and other marine aids to navigation and maintained by or under authority of
the U.S. Coast Guard
Lights and other marine aids to navigation, maintained by or under authority of the U.S. Coast Guard and located on waters used by general navigation, are described in
the Light List
The Light List is published in
seven volumes, covering all waters of the U.S. and its possessions.
The light list includes all
Coast guard aids to navigation used for general navigation such as lights, sound signals buoys, and daybeacons.
The light list does not include
Coast Guard mrooring buoys, and some buoys having no lateral significance such as special purpose, anchorage, fish net and dredging .
The Light List is published via hardcopy
annually
The electronic version of the Light List is updated
weekly
Changes to aids to navigation during the year are published in
U.S. Coast Guard Local Notices to Mariners and National Geospatial Intelligence Agency (NGA) Notices to Mariners.
A summary of corrections for the Light List, which includes corrections from the dates shown on the title page to the date of availability, is published in
the Local Notice to Mariners and the Notice to Mariners.
Names of aids to navigation are printed as follows to help distinguish at a glance the type of aid to navigation listed:
Seacoast/Lake coast Lights and Secondary Lights RACONS Sound Signals River, Harbor, and Other Lights Lighted Buoys Daybeacons and Unlighted Buoys
Aids to navigation are numbered by in accordance with their order of appearance in each volume of the Light List. Other numbers and decimal fractions are assigned where newly established aids to navigation are listed between previously numbered aids to navigation.
fives
International numbers are assigned to certain aids to navigation in cooperation with t
he International Hydrographic Organization. They consist of an alphabetic character followed by three or four numeric characters.
The visibility of a lighted aid to navigation depends upon two factors:
Intensity of the light (candlepower)
Its height above water
With regards to lighted aids geographic range is
the maximum distance at which a light may be seen in perfect visibility by an observer at sea level.
With regards to lighted aids, computed range is
the geographic range plus the observer’s distance to the horizon based on the observer’s height of eye.
With regards to lighted navigations aids, computed visibility is
the visibility determines for a light using the light’s height, nominal ranges and the height of the eye of the observer
For a lighted navigational aid, luminous range is
the maximum distance at which a light may be seen under the existing meteorological virility conditions. This does not take the height of the light, the overseas heat or the curvature of the Earth into consideration. It is only based on the intensity of the light.
With regards to lighted navigational aids, the nominal range is
the maximum distance a light can bee seen in clear weather, which is defined as a visibility of 10 nautical miles. This only depends on the intensity of the light
Are oil well strictures listed on the Light List?
No
What is the primary means for disseminating information concerning aids to navigation, hazards to navigation and other items of marine information of interest to mariners not he waters of the U.S.
Local Notice to Mariners (LNM)
Who is responsible for developing and issuing the LNMS?
Each Coast Guard District with information received fromCoast Guard field units, the general public, the Army Corps of Engineers, U.S. Merchant Fleet, National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS), and other sources, concerning the establishment of, changes to, and deficiencies in aids to navigation and any other information pertaining to the safety of the waterways within each Coast Guard District. This information includes: Reports of channel conditions, obstructions, hazards to navigation, dangers, anchorages, restricted areas, regattas, information on bridges such as proposed construction or modification, the establishment or removal of drill rigs and vessels, and similar items.
a series of nautical books that cover a variety of information important to navigators of coastal and intracoastal waters and the Great Lakes. Issued in nine volumes, they contain supplemental information that is difficult to portray on a nautical chart.
The United States Coast Pilot
Topics in the Coast Pilot include
Channel descriptions, anchorages, bridge and cable clearances, currents, tide and water levels, prominent features, twofers, pilotage, weather, ice conditions, wharf descriptions, dangers, routes, traffic separation schemes, small-craft facilities and Federal regulations applicable to navigations
a reference publication depicting basic chart elements and explains nautical chart symbols and abbreviations associated with NOAA and NGA charts.
Chart No. 1: Nautical Chart Symbols, Abbreviations and Terms. The Tenth Edition dated November 1997 is the current edition number.
The direction and velocity that a vessels moved off of its intended course due to the effects of wind and current are
set and drift
Anticipated set and drift can be determined by
eferencing a variety of publications, including current charts, PC-based current programs, and the current tables produced by the National Ocean Survey (NOS) branch of NOAA.
With a GPS coupled with an autopilot, the effects of set and drift (called “cross-track error” in GPS terminology) can be
compensated for automatically, saving considerable time, and fuel, in a long journey.
The Dead Reckoning Plot conoids of only two elements
course and speed
If offshore waters DR plots are often calculated for
every hour or half hour. In restricted waters every 15 minutes
Dead Reckoning is your intended or assumed path through the water. Dead Reckoning is based on: a, COURSE (direction traveled in either TRUE or MAGNETIC) b, SPEED & TIME (distance run)
A dead reckoning is
prepared as you go reflects actual progress reflects actual starting time reflects actual fixes reflects near term planning is updated after each fir
A new DR plot me be started after
every good fix, or course or speed change.
STW =
peed through the water.
Do NOT consider the effects of Current or the effects of Wind
COA
Course of Adance. The direction of the intended path over ground
SOA
Speed of Advance. The speed intended to be made over ground along the COA
COG
Course Over Ground, Instantaneous direction of the actual path over ground
SOG
Speed over ground. Speed made good at any instant along the
STW
Speed through water
CMG
Course Made Good. The resultant direction fro the beginning of the voyage to the end.
SMG
Speed made good. The overall actual speed of the voyage
EP
Electronic position. This is your real position (Fix)
PTA
Point to Aim. This is the course to steer to adjust for the current (PSC).
Purpose of a DR Plot
a, Before sailing (voyage planning):
b, Determine course and speed to make.
c, Identify checkpoints and waypoints,
d, Locate fuel and other needed stops.
e, Estimate: Fuel, time, and other parameters.
f, While underway to plot or follow actual progress.
RULES FOR A DR PLOT
1, A DR plot is based only on course and speed through the water
2, A DR position is plotted at convenient time intervals , eg every 30 or 60 minutes
3, A DR position plotted whenever a fix, running fix, or line of position is determine
4, A DR position plotted whenever a course or speed change occurs
5, A new DR plot should be started whenever a fix or running fix is obtained
BOW BEAM BEARINGS
When running along the coast within visual sight of land, there is a simple method of determining distance offshore, which may be necessary to avoid a shoal or other navigational hazard. This method is called bow beam bearings, and sometimes called “doubling the angle on the bow.”
This method is based on the geometric fact that two sides of a 45° right triangle are equal. When some landmark (lighthouse, tank, etc) at or near the shoreline bears 45° relative, make note of the time and vessel speed. When the landmark is at 90° relative, the distance from the time of the first sighting is equal to the distance off.
RUNNING FIX
Inevitably, there will be times when a sufficient number of landmarks are not available to take a 3-LOP fix, either due to weather, insufficient landmarks, or when landmark angular separation is unsatisfactory. In these instances, a single LOP can be “advanced” to create a reliable fix.
