OUPV / Six Pack Captains License Course

NAVIGATION GENERAL - Aids to Navigation

Navigation General

Aids to Navigation - Introduction

Navigation General consists of buoys, lights, charts, weather, tides and tidal currents, electronic navigation, and marine radio telephone. The final exam for this module has a total of 50 open book, multiple choice questions requiring a minimum score of 70% to pass.”

Navigation is finding your position and calculating distances measured on the surface of the earth.  Electronic Navigation is piloting by using electronic devices, most commonly a GPS.  This will be covered later in this module.  Celestial Navigation is determining your position using the sun, stars and moon, usually with the help of a sextant.  Dead Reckoning is the process of determining a vessel’s approximate position by applying speed, time, distance and course steered from its last known position (this process does not account for set (direction) and drift (speed) of a current).

We will focus on navigating using aids to navigation (range markers & light houses), landmarks (flag poles & micro towers), and water depths, which is chart navigation.  This type of navigation utilizes charts, parallel rulers and dividers, and a compass.  Parallel rulers and dividers are used to plot points accurately on charts.

Charts are Mercator Projections, which provide equal expansion in all directions, thus flattening out the spherical earth onto a flat surface (chart).

Latitude Lines are parallel, running east and west around the earth.  They are measured north and south (ladder-up scale i.e. the rungs of a ladder), with the equator being the zero mark.  The North Pole would be 90 degrees North and the South Pole would be 90 degrees South.  Latitude is measured in degrees, minutes, and seconds. 1 degree of latitude is equal to 60 minutes.  1 minute of latitude is equal to 1 nautical mile.  This is where the term “a mile a minute” comes from.  On a chart, latitude lines can be used to measure distances, but never longitude, except at the equator.

Longitude Lines run north and south but are measured east and west. They are widest at the equator and come together at the poles.  These lines are not parallel.  The Prime Meridian, which goes through Greenwich, England, is zero degrees.  These lines go from 0-180 degrees, with 180 degrees being the exact opposite side of the earth from the 0 degree line.  Any point on a nautical chart can be expressed using latitude and longitude, with the latitude number always being given first.

A nautical chart is a flat graphic representation of a navigational portion of the earth’s surface.   In this course you will be using a training chart, which is not used for actual navigation. A chart shows the depth of water by numerous soundings.   Depths of water may be in feet, meters (1 meter=3.3 ft.), or fathoms (1 fathom=6 ft.).  Sometimes shallower depths are shown in a different color, such as blue. Deeper navigable waters are white. Charts also show land areas, shorelines, and topographical features.  Land areas are often shown using a different color, such as brown (buff).   The most important information on a chart includes lights, buoys and other aids to navigation and is depicted by symbols.  These symbols have information about what the mariner would observe both during the day and at night.  Charts include information on bridges, cables, wrecks, and other information of interest to mariners.  Charts assist the navigator with arriving safely at a destination and avoiding dangers. Today’s mariners tend to rely on their GPS, but a chart should always be available as a backup in the event that the GPS goes out.  Local charts are required on certified boats. Coastal charts of U.S. waters are published by the National Ocean Services (NOS).

Aids to Navigation

An Aid to Navigation is any device not part of a vessel that is intended to determine position or safe course, warn of dangers or obstructions, or to assist in navigation.  This would include buoys, beacons, and other such aids.  They act much like traffic signs and lane markings that guide motor vehicles on the road.  The United States Coast Guard maintains these aids to navigation, including the daytime visual system of daymarks, beacons and buoys as well as the nighttime visual system of lights and retroreflective signals.  Any mariner that notices an aid to navigation off station should immediately contact the U.S. Coast Guard by radiotelephone.  The U.S. Coast Guard relies on all mariners to assist in keeping local waters safe to navigate.  The Local Notice to Mariners is a free publication that apprises mariners of changes and updates in navigational aids and inaccuracies in chart information.  The Local Notice to Mariners can be accessed online through the Navigation Center. They also publish an annual compilation of all changes that occurred throughout the previous year.

Buoys are floating aids to navigation that mark channels, indicate shoals and obstructions, and provide warnings for mariners.  Their color, shape, top mark, number, and light characteristics indicate to the mariner how to navigate to avoid hazards and remain in safe water. 

The Lateral Buoy System indicates the sides of channels or routes.  They also mark junctions where two channels meet.  Remembering the phrase “Red, Right, Return” assists mariners in knowing which side their vessel should pass the lateral marks on.  When returning from the ocean, red buoys are on the vessel’s right side and green should be on the left side.  Solid colored red or green buoys are numbered.  Red buoys are even numbered (starboard buoys) and green buoys are odd numbered (port buoys).  The numbers on the buoys increase as a vessel proceeds from the sea.  Can Buoys are green and mark the port side of a channel and Nun Buoys are red in color and mark the starboard side of a channel.  Lateral buoys are the only buoys that utilize a numbering system.  At night lighting of the lateral buoys is extremely important.  The buoys flash at different patterns so that the mariner does not get confused as to which buoy is next.  Information about the light pattern for each buoy is listed on the nautical chart for the area.

The Lateral Buoy System also includes Preferred Channel Buoys.  These may be lettered but are never numbered.  The topmark of the buoy indicates which side the vessel should pass on.  If the buoy is lit, the light will match the topmark. They have red & green horizontal bands

There are other Aids to Navigation that do not have lateral significance.  These include isolated danger, safe water, range dayboards or markers, information and regulatory marks, and special marks.  Aids that do not have lateral significance are never numbered but may contain a letter.

An Isolated Danger mark is black and red horizontally banded and may be letter but would have no numbers.  If lit, it would use a white light only, as shown below:

A Safe Water mark is the first buoy you would see coming in from the ocean and would indicate that the water is safe on both sides of the buoy.  It is the only buoy with a light that flashes Morse Code “A”, short-long the first letter of the alphabet.  It would also contain no numbers but could be lettered and would have a white light only, as shown below:

Range Dayboards are used to guide large ships through channels and may be lettered only. When a vessel is in the channel the range markers will line up properly. If a mariner finds himself to the right of a range they would steer to the left to get back into the channel.

Below or typical range dayboards:

Information and regulatory marks can vary in shape.  They are white with orange bands.  These would include speed limits, danger, restricted areas, etc.  If lighted, the light would be white.  Samples are shown below:

Special Marks are yellow in color and have no specific shape.  Yellow generally means “caution”, so these would be areas a mariner should slow speed and proceed with caution.  If lighted, the light would be yellow.  These would be used in anchorage areas, Marine Sanctuary, dredging and survey operation areas, and fish net areas.  Samples are shown below:

Buoys make poor fixes as they are subjected to tides and currents.  They also lean more in shallow water.  A Station Buoy is a replacement buoy and would match the buoy it replaces both in color and lights. The following page shows the Aids To Navigation together, and this can be found in the Light Lists as Plate 1.  The next two pages show a simulated area with channels and obstructions.  The first picture shows what the buoys would actually look like in the simulated area in the day time, while the second picture shows the same simulated area at night.  The third picture shows what the buoys would look like on a chart (chart symbols).

Aids to Navigation marking the Intracoastal Waterway (ICW) display unique yellow symbols to distinguish them from aids marking other waters.  Yellow triangles indicate aids should be passed by keeping them on the starboard (right) hand of the vessel.  Yellow squares indicate aids should be passed by keeping them on the port (left) hand of the vessel.

Practical Exercise: Study the above three Fictitious Nautical Charts and Aids to Navigation Plate 1.  Compare the day and night aids as well as the chart symbols to the Aids to Navigation to learn the meaning of each. 

Light Lists are published by the United States Coast Guard, who also maintains the lights.  Red Lights are used only on red buoys or Preferred Channel Buoys whose topmost band is red.  Green lights are used only on green buoys or Preferred Channel Buoys whose topmost band is green.  Yellow lights are used on Special Purpose Buoys.  White lights may be used on buoys with no lateral significance.  Safe Water buoys that could be passed on either side would flash white Morse Code “A” (short-long).  White lights may also be used on Isolated Danger Buoys or Regulatory Marks where there is no lateral significance.

Lights are installed on Aids to Navigation to provide signals to identify one navigational light from another.  The time required for a lighted aid to complete a full cycle of light change is called its period.  A light having characteristics which include color variation is defined as alternating.  Lights with lateral significance display either flashing, quick-flashing, occulting, or isophase.  In Flashing Lights, the duration of light in each period is shorter than the duration of darkness and the flashes of light are equal in duration.  A Quick-Flashing Light flashes 60-80 flashes per minute.  Occulting Lights show longer periods of light than dark.  Isophase Lights show equal periods of light and darkness.  Composite Group Flashing Lights usually indicate a bifurcation or junction and the flashes are combined in successive groups of different numbers of flashes.  Below is a list of light flashes with their abbreviations from a U.S. Coast Guard Light List publication (note the abbreviation in the last column):

Sector Lights are sectors of color that are displayed on lantern covers of some lighthouses to indicate danger areas.  A red sector indicates that a vessel would be in danger of running aground while in the sector.  Sector bearings are true bearings and are expressed as bearings from the vessel towards the light.

Bridges across navigable waters are generally marked with red, green and white lights for nighttime navigation.  Three white lights in a vertical line above a green light mark the preferred channel. Know your bridge clearances found on charts and coast pilots.

Practical Exercise:  Read the pages of the partial Light List that is included in your materials.  An exam copy of the Light List will be available for you to use during your final exam.  The ability to utilize a Light List is important for navigating your vessel particularly in unfamiliar waters.

Look at the cover page and note that the Light List is published by the United States Coast Guard (USCG). Note also the date of publication.  The next page shows the limits of Light Lists and which zone is covered by each volume.  Find the volume for your area. The next few pages show the U.S. Aids to Navigation and Fictitious Nautical Charts shown above.  Page C1 shows the luminous range diagram of lights.  The Table of Contents shows the pages specific information is on.  The next page lists the District Commanders with their contact information. Find your district and the contact information for your District Commander. The Preface includes the web address for the electronic light lists.  The Introduction is one of the most important informational pages as it includes the description of each column of the Light List.  Find the section “Description of Columns” and read through all 8 columns. 

These will be listed at the top of each column when looking up a specific light.  Read through the remainder of the informational pages.  You will then find a Glossary of Aids to Navigation Terms, which contains definitions of key words.  Read through the Glossary and Abbreviations, and use this information as needed.  The next page, the Characteristics of Lights, is referenced and discussed above.

To use a Light List Publication you would find the light you are looking for in the Index in the back of the publication.  Note the reference number and find that number in the light list area.  Remember to look at the top of the 8 columns to find the information they show.

Practical Exercise:  Utilizing the Light List for your area, find the major light features and what the symbols mean. http://www.navcen.uscg.gov/?pageName=lightlists Click on your district and find information regarding lights in your area.

Coast Pilot

The Coast Pilot is a publication much like a cruising guide that contains information on a specific area, including anchorages, landmarks, navigation regulations, channels, controlling depths, dangers and obstructions, and much more.  These are published by the National Ocean Service (NOS) and can be accessed online at https://nauticalcharts.noaa.gov/publications/coast-pilot/index.html  

Practical Exercise:  Utilizing the Coast Pilot for your area, find the major information for your location. https://nauticalcharts.noaa.gov/publications/coast-pilot/index.html  Click on the bar that says “Coast Pilot Search”.  Enter your Chart Number or geographic location and review the information provided by the Coast Pilot.  Remember that information is only accurate to the date of publication.