Aids to Navigation Charts
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Tides
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Aids to Navigation: Buoys and Daymarks:
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Buoys: All buoys float.
You will come across three types of buoys: Navigational, mooring, and
fishing. Mooring buoys are used to tie a boat to.
Never tie a boat to a navigational buoy, it is against the law.
Fishing buoys are usually used to mark fishing nets, crab traps etc.
One should try to avoid
these. They usually indicate shallow water and their line may foul
(get caught in) your prop, especially if you are under power.
Navigational
buoys are used as an aid in navigating your
boat. Green buoys have odd numbers. To the right is a lighted
green buoy (with seals) and an unlighted green buoy with a flat top, also
called a can. When returning from sea
these buoys should be kept to port. (IALA-B International Maritime Buoyage
System)
Red buoys
have even numbers. To the right is a lighted red buoy (with seals)
and an unlighted red buoy with a pointed top, also called a nun.
When returning from sea
these buoys should be kept to starboard.
( IALA-B International Maritime Buoyage System )
Daymarks: All daymarks
are on pilings and are numbered. Red daymarks have even
numbers and are triangular. Green daymarks have odd numbers and are
square. Daymarks have the same meaning as buoys but are placed in
shallower water.
If you are trying to stay
within a channel, never maneuver a sailboat between two buoys or daymarks
that have the same color.
The
picture on the right shows a sloop leaving the harbor with a lighted red daymark off its port and a green daymark off its starboard side.
(Picture Courtesy of Whitaker Creek Yacht Charters, NC)
With a few exceptions, the intracoastal
waterway (ICW) has red daymarks on the side of the mainland shore. Thus, on the Atlantic Coast
the red daymarks are on the starboard side when heading south. The
opposite would be true if your are heading south on the west coast of
Florida. The
exception is when one is heading south on the Atlantic
Coast and out a channel. In this case, the yellow symbol on
the intracoastal
waterway daymarks must be used to determine the direction and position of
the ICW.
The daymark shown on the
right is sometimes found at the junction of a channel and the ICW.
It should be kept to PORT for vessels following the channel inland from
the sea. However, it should be kept to STARBOARD for those vessels
following the ICW
from New England to Texas
(and kept to PORT for those traveling the ICW from Texas to New England).
For more information on Aids to Navigation (ATON) view the
USCG Powerpoint Presentation
in HTML format.
( Download
PowerPoint File 6.85 megs )
Sailor's Tip: Red
Right Returning. In the intracoastal waterways on the Alantic Coast
remember Red Right Passing Clockwise New England to Texas .
(Note: The above information applies to
the IALA-B, International Association of Lighthouse Authorities - Region B
Buoyage System, which is found in the
Eastern Pacific, Atlantic and Pacific Coasts of North and South America,
the Great Lakes, the Caribbean, Japan, Philippines and the Republic of
Korea. Most of the rest of the world follows the IALA-A system
(green right returning) which is found in the remainder of the Western
Pacific, Indian Ocean, Atlantic Coasts of Africa and Europe, and the
Mediterranean.)
Charts
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Click on Pictures to
Enlarge !!!
The Office of Coast Survey (OCS) produces
nautical charts for United States waters. OCS is an office within the
National Ocean Service, NOAA. It is the oldest U.S. scientific
organization dating back to Thomas Jefferson who established the office in
1807 to encourage safe and efficient commerce.
Chart symbols are contained in a publication
"Chart No.1 Nautical Chart Symbols Abbreviations and Terms".
You may order this publication from NOAA or view it online in PDF format: To view publication
click on the screen button to the right.
Locations
on charts are given in
degrees, minutes and seconds of longitude and latitude. Degrees of
longitude are displayed on the top and bottom of the chart (running east
to west) and Degrees in latitude are displayed on the sides of the chart
(running north to south). One nautical mile is equal to one minute
of latitude.
Water depth is measured in feet, meters or fathoms.
Six feet equals one fathom. Under the chart's name, will be listed
whether the soundings are recorded in feet, meters or fathoms. In this area
the scale of the chart will also be found.
Before entering a harbor, dock or anchorage go online and obtain free
tide tables and graphs, detailed nautical maps and aerial photographs.
The Speed - Time - Distance Calculations
are
one of the basic tools a sailor needs in navigation. Using this
simple formula one can predict the time of arrival, the speed of travel
or the distance and with a known heading, determine an approximate position (Dead Reckoning -
DR )
Go To:
Speed Time Distance Calculator
Time = Distance / Speed
Distance = Time
* Speed
Speed = Distance / Time
Distance is in nautical miles, Speed is in
knots and Time is in hours. If minutes are used, the time in the
above equations is divided by 60.
The speed of the boat is measured by the
boat's knotmeter or speed log. If this instrument is not
functioning, the boat's speed can be calculated by measuring the time a
floating object takes to pass the boat:
Go
To: Boat Speed Calculator
Currents: Make sure you know
if tides and currents are prominent in the area you are sailing.
If they are, you may have to steer a different course (course to
steer) to sail in the desired direction (course to make good).
Go To Current &
Tide Page
Go To
Course to Steer Calculator
Tide Prediction Through 2038 - Program by Mike
Hopper
The program is freeware and predicts tides around the world.
Select a tide station from a map or list and a tide chart will be
displayed.
( Download Zip File and Unzip, Select "SETUP.EXE" to install program. )
Fix: A fix is the position of your
boat based upon two or more bearings (three or more is preferable), or by
determining the distance from (Distance Off) and a bearing to a known
object (such as a lighthouse). The Distance Off can be calculated by
using a sextant to determine the angle to the top of an object of known
height. This distance is used to determine a Circular LOP (circular
line of position).
Distance = Height / tangent (Degrees)
Another way of determining position is using a
Landfall Fix. This method uses a bearing from a lighthouse and the
position the lantern's light is first observed.
Go To
Landfall Fix Calculator
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Compass Rose : All navigational charts have one or more
compass roses. This inner circle shows degrees in relationship
to magnetic north and the outer circle is degrees in relationship to
true north. True north is what can be measured by your GPS and
magnetic north is what is shown on your ship's compass. True
North is
the point on the earth's surface where the axis of rotation passes
through. The
difference between the two is called magnetic variation and can be calculated from
the compass rose.
Download
Pangolin Communication's
Magnetic Variation Calculator
http://www.pangolin.co.nz/free_stuff.php
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There are three methods of recording
and determining direction:
--True: In relationship to true north
--Magnetic: In relationship to magnetic north.
The location of "Magnetic North" changes slightly each year.
This variation is listed below the center of the compass rose.
--Compass. This heading takes into account compass
deviations from magnetic north. Compass deviation can be
caused by many factors such as the ship's engine, an iron keel and
excessive heeling of the boat, etc. This deviation will often
vary depending upon the the course of the sailboat.
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Parallel Ruler : A
parallel ruler can be used to chart a course. The edge of one
ruler is placed on the chart over the desired course and the edge of
the other ruler is placed through the center of a compass rose.
The course heading can now be determined. |
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Red and Green Daymarks and a lighted green daymark. In
this figure the green daymark is shown as a box G "3" and the red daymark is shown as a triangle R "2A". The numbers and letters
in quotes denotes the markings on the daymark. Note the
lighted day mark which looks like an explanation point.
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Lighted Daymarks : Both green and red lighted daymarks are
shown by the same symbol. You must read the labeling to tell
the difference. In this example, the lighted daymark is denoted
by FL R 2.5 s 15ft 5M "4" This stands for:
Flashing Red daymark at 2.5 seconds, 15 feet high and seen for 5 Miles
on a clear night. A number "4" is marked on the daymark.
Note the shipwreck symbol with a PA for "position approximate" in
the upper left-hand corner.
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Red and Green Buoys and a lighted red daymark. Shown
here are two red and one green buoy. The red buoys are in the
upper left-hand corner, marked R N "4" (Red Nun marked #4), and lower figure,
marked R N "8". The green buoy, middle of the figure, is
marked G C "7" (Green Can marked #7). Also note the lighted red daymark denoted by
Fl R 5M "6" (Flashing, Red daymark, seen for 5 Miles on a
clear night and marked #6) (lower case "m" represents meters,
upper case "M" represents nautical miles.)
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Lighted Buoys : Lighted buoys have a red circle at the
bottom of the symbol. Note, that unlike daymarks, different
colors are used for lighted red and green buoys.
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