Download Boating Tip #11: Obtaining a Visual Fix (PDF format, 26KB)

A fix is a known position determined from the intersection of at least 2, and preferably 3 lines of position (LOPs). Mark a visual fix on your track line as a point inside a circle

3 Line of Position Fix

You can find where you are (get a fix) by using visual bearings and lines of position. Use points of land, navigational aids or landmarks identifiable on a chart and which can be easily seen. If necessary, a fix by sounding can be obtained using a depthfinder by noting when you pass charted bottom contour lines and using them as lines of position.

Use a hand bearing compass to obtain 3 bearings from your position on objects on shore that are widely spaced. Ideally the 3 objects should be equally spaced about 120° apart from each other. A 3 LOP fix will be more accurate if you are not moving and dead in the water. If you are moving, take the reading off the beam first.

Correct the 3 compass bearings to true using the CDMVT memory aid. Assume the deviation of a hand bearing compass is zero since it can be moved about the vessel. Since all 3 bearings are taken from the same geographic location, they will all have the same variation.

Plot the true bearings, now called lines of position (LOPs) from the vessel on the chart. The center of the small triangle (cocked hat) where the 3 LOPs converge (or if very accurate, at the point where they intersect) is the fix.

Running Fix

A running fix can be used when only one object is available using bow and beam bearings. Take the first bearing using a hand bearing compass when the object is 45° from the bow of your vessel. Take the second bearing when the object is 90° abeam. Use elapsed time, speed and 60 D ST to find distance. The distance the boat travels (distance run) in the time between the bow and beam bearings is equal to your distance from the object.

Download Boating Tip #10: Geographic Coordinates (PDF format, 23KB)

Geographic coordinates are measured in degrees, minutes and tenths of a minute (or seconds). One degree is 1/360th of a circle, one minute is 1/60th of a degree, and one second is 1/60th of a minute. More commonly today, 1/10th of a minute is used instead of seconds in recording position.

Parallels of latitude run parallel to the equator and are measured north or south of the equator up to 90°. The equator is at 0° latitude. The poles are at 90° latitude (north or south). Parallels of latitude are equally spaced and 1 minute of latitude is equal to 1 nautical mile. Distance on the water is always expressed in nautical miles. One nautical mile equals 6,076 feet or 1.15 statute miles. One degree (1°) of latitude equals 60 nautical miles, and one minute (1′) of latitude equals 1 nautical mile. Each minute of latitude can be broken into seconds (“), or tenths of a minute.

Meridians of longitude run north and south. The prime meridian (0° longitude) runs through Greenwich, England. Longitude is measured east and west of the prime meridian from 0° to 180°. The International Date Line is at 180°. At the equator, each 1° of longitude is about 60 nautical miles apart, but degrees get closer together until they meet at the poles.

Because a nautical mile is equal to 1 minute of latitude, distance between two points plotted on a chart can be easily measured. Set your dividers to a known distance and walk them along your course. Or, for short distances, extend the dividers, and without changing their spacing, move them to the nearest latitude scale and count the distance.

You can also determine your distance north or south of the equator by using latitude. Multiply degrees of latitude by 60 nautical miles. To that sum, add the minutes of latitude. For example, San Diego Bay is located at 32° 43′ north latitude. 32° 43′ N is (32° x 60 nm) + (43′ x 1 nm) = 1,963 nautical miles north of the equator.

Download Boating Tip #9: Tides & Currents (PDF format, 38KB)

Tides

• Tide is the vertical rise and fall of the ocean level resulting from forces of gravitation
• The moon exerts the primary force on tides
• The sun also exerts a force on tides but less than the moon, because although the sun is larger, it’s further away
• High tide is the highest water level in a cycle
• Low tide is the lowest water level in a cycle
• Stand of a tide is the period in the tidal cycle in which the level appears not to change
• Range is the difference between the height of high tide and low tide
• Time difference between one high tide and one low tide is approximately 6 hours and 12 minutes.
• Mean low water is the average of all low tides
• Mean lower low water is the average of the lower of two low tides occurring within a day
• Actual depth of water equals the depth on the chart plus the height of the tide
• Spring tides occur when the sun and moon act together at times of new or full moon. Spring tides occur throughout the year, not just during the Spring season. High tides are higher and low tides are lower than normal during spring tides.
• Neap tides occur when the sun and moon act in opposition. The smallest tide range occurs during neap tides.

Currents

• Currents are the horizontal movement or flow of water between the ocean and coastal waters
• There are two types of currents: ocean currents and tidal currents
• Ocean currents result from effects of winds, salinity and temperature differences in the water (For example: the Gulf Stream, California Current)
• Tidal currents result from tidal changes
• Strength of the current depends on the point in the tidal cycle and land configuration
• Strong currents are predicted when a large amount of water has to move through a small land opening
• Flooding means the current is moving toward shore and the tide is rising
• Ebbing means the current is moving away from shore
• At slack water, there is no detectable horizontal movement of water
• Currents on the North American Pacific Coast typically have diurnal inequality which means there is a difference in two consecutive ebb or flood maximums due to the effect of the moon.
• Usually there are 4 slack currents and 4 maximum currents each day.
• Currents can be altered by wind, weather, or river discharge, so actual speeds and times may vary from what is published.

Download Boating Tip #8: Boating Reference Publications (PDF format, 34KB)

In addition to charts, it is helpful to have several publications, including Coast Pilots, light lists, tide tables, current tables, Navigation Rules, and the Local Notice to Mariners onboard for reference and to assist with navigation.

Coast Pilot

The Coast Pilot is an official government publication similar to a cruising guide and includes information about areas in which you are operating. The Coast Pilot is published by NOAA by region. For example, United States Coast Pilot 7 is for the Pacific Coast: California, Oregon, Washington and Hawaii. It contains descriptive information about routes, applicable charts, approaches, aids to navigation, distances, weather information, anchorages, restricted areas, and hazards. It also includes navigation regulations, and useful general information on topics like pollution prevention, submarine identification signals, destructive waves, distress procedures, towing preparation, helicopter rescue. Coast Pilots can be downloaded as pdf files from www.nauticalcharts.gov/view

Light List

Light lists describe lights and buoys in the order you are likely to encounter them. Light Lists give the geographic range of lights, or how far you can see a light from a particular height. Chart acronyms, chart symbols, a glossary of terms, and index of light names are included. The light list should be corrected from the Local Notice to Mariners.

Local Notice to Mariners

The Local Notice to Mariners is published monthly and weekly by each Coast Guard District. It is no longer mailed weekly and free of charge to boaters. It is now available on the web at www.navcen.uscg.gov/lnm/d11. The Local Notice to Mariners lists special notices of interest to boaters, provides information about the status of GPS and LORAN, lists discrepancies or temporary changes (missing, inoperative, reduced intensity, damage) to aids to navigation, chart corrections, proposed changes in aids to navigation, and hazards to navigation.

The “Notice to Mariners” is also published weekly, by the National Imagery and Mapping Agency (NIMA), and provides information primarily for large vessels.

Tide Tables

Tide tables provide times and height differences for high and low water. Tide tables also provide sunrise / sunset and moon rise / moon set times.

To find the depth at a location, add the height from the tide tables to the charted depth. Use information for the reference station or correct for the subordinate station nearest where you are sailing. Remember to add an hour for Daylight Savings Time.

The official tide tables are published by International Marine for NOS of NOAA. Privately published almanacs, web sites and commercial tide tables are also available.

Current Tables

Current tables provide predictions on the horizontal movement of water, slack time or minimum current flow, and times of maximum flood for both ebbs and both floods, speed of a current in knots for flood and ebb, and the approximate true direction of currents. Current cannot be determined from tide tables. Information on currents is provided for primary reference stations and thousands of subordinate stations.

Usually there are 4 slack currents and 4 maximum currents each day, but currents can be altered by wind, weather, and river discharge, so actual speeds and times may vary from what is published.

Official current tables are published by International Marine for NOS of NOAA, and by the Canadian Hydrographic Service. Privately published almanacs, web sites and commercial current tables are also available.

Navigation Rules

Navigational Rules are the “rules of the road” under which boaters must operate. They are published by the U.S. Department of Homeland Security for the United States Coast Guard. The text includes both Inland Rules and International Rules. International and Inland Navigational Rules and their Annexes are similar in content and format, but there are some important differences.

The Inland Rules replace the old Inland Rules, Western Rivers Rules, Great Lakes Rules and parts of the Motorboat Act of 1940. They were adopted by Congress as the Inland Navigational Rules Act of 1980, and became effective December 24, 1981 (except on the Great Lakes where they went in to effect on March 1, 1983).

The International Rules, commonly referred to as the 72 COLREGS, were formalized at the Convention on the International Regulations for Prevention of Collisions at Sea. They were adopted by Congress as the International Navigational Rules Act of 1977, and became effective on July 15, 1977. The International Maritime Organization (IMO) adopted 55 amendments (effective in 1983), and 8 more amendments (effective in 1989). The International Rules are applicable on waters outside demarcation lines.

Download Boating Tip #7: Course Correction (PDF format, 32KB)

The magnetic north pole moves. The true north pole is at 90° north latitude. Currently the magnetic north pole is at 74°N 101° W, in Canada below the true north pole. True and magnetic poles do not coincide, nor do true and magnetic meridians. The difference between the true and magnetic meridians is called variation. Because you read true course on a chart, but steer the compass course, you need to know how to convert from one to the other.

Variation

Variation is the angular difference between magnetic north and true north. Nautical charts are drawn using true north. Always add westerly variation and subtract easterly variation when converting from true to magnetic, and vise versa when converting from magnetic to true. To find variation in the area where you are sailing, look at the center of the compass rose on a chart.

Compass Rose

The compass rose is a set of concentric circles printed on a chart. The outer circle has 0 (zero) at true north and is marked with a star. The inner circle shows magnetic north and is marked with an arrow. The difference between the 0 on both circles is the magnetic variation at the location where the compass rose is positioned. The variation east or west is labeled in the center of the compass rose along with the annual rate of change in variation. Always use the compass rose closest to the area where you are plotting on the chart.

Deviation

Deviation is the onboard electrical or magnetic variation, or the magnetic error caused by the vessel and its mechanical and electrical equipment. Deviation changes as equipment is moved or brought aboard. Deviation must be corrected for each heading. A compass can be “swung” to determine deviation at each point. You can also find the deviation at each point by comparing the reading on your magnetic compass from the true heading displayed on a GPS or auto pilot fluxgate compass.

TVMDC

TVMDC (True Variation Magnetic Compass add West) is used for uncorrecting the compass to determine the compass course to steer. When converting from the true course plotted on the chart to the compass course you want to steer in order to get to your destination, use the memory aid “True Virgins Make Dull Company add Whiskey”. Add westerly variation and subtract easterly variation when converting from a true to magnetic course.

CDMVT

CDMVT (Compass Deviation Magnetic Variation True add East) is used for correcting the compass to determine the true course to plot. When converting from compass course to true course, use the memory aid “Can Dead Men Vote Twice at Elections”. Add easterly variation and subtract westerly variation when converting from a magnetic to true course.

Finding Compass Error

Compass error is the sum of variation and deviation, or the difference between true and compass readings. To find compass error, add the variation and deviation and indicate the direction east or west of the error. For example, if variation is 13° E and deviation is 1° W, the compass error is 12° E.

Range

A range is two objects identified on a chart which line up with the bow (or beam or stern) of the vessel.

To find deviation from a range, find the true direction from one charted object to the other. Uncorrect from true to compass using TVMDC. Fill in true direction and magnetic variation from the chart to find the magnetic bearing. Fill in the compass bearing from your handheld compass. The difference between the magnetic and compass bearing is the deviation. Find direction of the error using the memory aid “If the compass is best, the error is west. If the compass is least, the error is east.”

Download Boating Tip #6: Plotting Tools (PDF format, 62KB)

In order to navigate safely, you need certain tools. Plotting tools which should be aboard every boat include: paper charts, a magnetic compass and a separate hand bearing compass, parallel rulers or a course plotter, a triangle, dividers, pencil and eraser, depth sounder, knot meter, and a clock. A magnifying lens, binoculars, and calculator are also recommended. Reference books such as GPS waypoints, the Coast Pilot, current and tide tables, light lists, cruising guide, Chart #1, Navigation Rules, and Local Notice to Mariners will also provide valuable information in helping you to navigate.

Traditionalists may have celestial navigation instruments, including a sextant aboard. On a modern recreational vessel you may also have electronic instruments to help you navigate, such as: global positioning system (GPS), radio direction finder (RDF), radio detecting and ranging (RADAR), sonic ranging (SONAR), long range navigation (LORAN), chartplotters or a computer with navigation software and raster or vector charts installed.

Charts

Charts are maps designed for navigating on the water. U.S. charts are published by the National Ocean Service (NOS), a division of the National Oceanic & Atmospheric Administration (NOAA), an agency of the U.S. Government. Charts show soundings, fathom curves that connect points of equal depth, shoreline, landmarks, buoys, light visibility range, positioning of aids to navigation, heights, traffic separation schemes, and hazards. The correction date of the last weekly Notice to Mariners applied to the chart is shown on the lower left border of the chart. Paper charts, waterproof paper charts, spiral bound chart books, and computerized charts are also available.

Mercator projection charts are most commonly used for coastal navigation. Flemish geographer, astronomer, theologian and cartographer Gerhard Kramer (AKA: Gerhardus Mercator) published his first, very accurate for its time, worldwide ocean navigation chart in 1569. Mercator charts are cylindrical projections tangent to the earth at the equator then flattened out. They allow latitude and longitude from a spherical earth to appear as horizontal and vertical lines on a flat chart. Relative size of features on the chart are distorted, but correct angular relationships between points on the chart is maintained. Most importantly, they permit sailing from point to point on a straight course.

Charts come in three types: general or small scale charts, coast or medium scale charts, and harbor or large scale charts. Large scale charts cover a small geographic area, while small scale charts cover a large area in great detail. Scale is written as a ratio. For example, a chart scale of 1: 50,000 scale means 1″ on the chart is equal to 50,000 real inches.

In order to interpret the information and symbols on a chart, refer to Chart #1. Today Chart #1 entitled “Nautical Chart Symbols, Abbreviations and Terms, USA” is published in booklet form. It includes 5 sections (general, topography, hydrography, aids and services, and an alphabetic index), and 24 subsections:

Finding Compass Course

A magnetic compass uses the earth’s magnetic force to determine direction the boat is heading. It is a simple and reliable device. A magnetic compass will usually continue to operate even if there is a power failure, fire, collision, or grounding. Use the compass card for reading course direction while looking at the lubbers line. The lubbers line is a reference mark on the inside of the compass bowl that is aligned with the ship’s keel. The binnacle is the non magnetic housing which supports the compass.

A hand bearing compass allows you to simultaneously look at an object and the compass scale. Readings taken from a hand bearing compass allow you to determine the bearing or direction of another object in relation to your position on the boat. A hand bearing compass can help you plot your position, can be used to determine if you are on a collision course with another boat, and can tell you if you are dragging at anchor.

Finding Direction

Course plotters are clear, rectangular straight edges, overlaid with protractor scales and parallel lines. To use a plotter, place the plotter on the chart and align the straight (top) edge along the course. Roll or slide the plotter across the chart by applying pressure with one hand, so the center point on the compass printed on the plotter is on any meridian. Read the course at the point on the edge of the compass that lies on the meridian to determine direction. Similarly, parallel rules can be walked across the chart from the DR to a compass rose printed on the chart.

A triangle can be used instead of a compass rose to determine direction. Keeping aligned with your parallel plotter, move the triangle to a meridian. When 0 touches a meridian, read the edge of the compass to determine direction. Remember “East is least. West is best.” When heading in an easterly direction read the numbers less than 180°. When heading in a westerly direction, read the numbers greater than 180° on the triangle. Chart lines are always drawn in relation to true north, but you steer a compass course. Remember to convert.

Measuring Distance

Dividers are used for measuring distance. For accurate measurements, make sure the leg points are sharp. Open and close dividers with one hand. Extend the legs and place one leg of the dividers on location A and the other leg of the dividers on location B. Take the extended dividers, without changing their spacing, to the nearest latitude scale on the side of the chart and count the distance. Remember 1 minute of latitude equals 1 nautical mile. Or, extend the dividers to a known distance using the bar scales, then walk the dividers along the course. Dividers can also be used to measure the location of a point using the closest line of latitude and longitude.

Measuring Speed

In the olden days, speed was measured with a chip log. A chip log was a piece of wood attached to a line with evenly spaced knots. The knots were counted as they paid out behind the stern of the ship over a certain amount of time. Today, boat speed, a measure of boat movement through the water, is measured with a knotmeter. A knotmeter is an impeller type underwater log. It uses a propeller which spins as the boat moves through the water. This produces an electrical impulse which is converted to a digital reading used to measure speed through the water. The paddlewheel is easily clogged with marine growth and needs frequent cleaning. To clean, remove the through hull paddlewheel, and temporarily replace it with the blank plug. After cleaning with a wire brush, remember to replace the paddlewheel facing the bow and in line with the keel from bow to stern.

Speed over ground is affected by current and wind, so boat speed through the water, and speed over ground are not necessarily the same. A GPS tells you speed over ground.

Measuring Depth

In the olden days, depth was measured using a hand lead line which was lowered to the bottom. Today, a fathometer (also known as a depthfinder or depth sounder) transmits a sound signal vertically and measures the time between the transmission of the signal and the return of the echo after bouncing off the bottom. Average speed of sound waves is 800 fathoms per second. Depth is half the distance the sound waves traveled. Depthfinders show present depth below the vessel on a digital display. Depthfinders that provide a graphic display of the boat’s path through the water are also available. Many depthfinders have shallow water alarms that you can set at a specific depth to warn you that you are entering shallow water, prior to running aground. Since the signal is sent from the bottom of the keel, depths recorded by the fathometer should be depth below the keel, not from below the waterline.

Download Boating Tip #5: Marine Navigation (PDF format, 37KB)

Marine navigation is the art and science of determining position of a ship and its movement from one location to another. The purpose of navigation is to keep track of where you are and where you are heading. To do this, various methods are used.

Dead reckoning

Also known as deduced reckoning. Position is determined from a fix or last known position, and the vessel’s direction and speed through water.

Piloting

Position is determined near shore using landmarks, soundings, and navigational aids.

Electronic navigation

Electronic devices are used to collect information on position.

Celestial navigation

Position is determined by observing celestial objects such as the sun, moon, stars and planets, and using celestial computations.

“If you don’t care where you are, then you aren’t lost”. But, most boaters want to know where they are when they are on the water. Navigation helps you find the answers to questions:

• Where am I starting from?
• Where do I want to go?
• How do I get from here to there
• Am I where I’m supposed to be? If not, how do I get back on course?
• Are there any hazards along the way that I should avoid?
• How far away is my destination?
• How long will the trip take?
• Will anything slow my progress or take me out of the way?
• When will I get there?
• How fast do I need to travel in order to get there by a certain time?
• What tools, “road signs” & “maps” are available to help me find the way?

The duties of the coastal navigator include collecting and recording data when: getting underway, leaving port, before losing sight of land, upon sighting land, when entering port, and after anchoring, docking or mooring. The navigator should identify all aids to navigation, and witness all course changes from on deck because of the close proximity of danger in near coastal areas. The navigator is also responsible for keeping a log.

Common Marine Navigational Errors

• Incorrectly identifying aids to navigation
• Not using charts, tables, lists, coast pilots and other reference publications
• Using out–of–date or uncorrected charts
• Failing to apply variation or deviation
• Not keeping a DR plot
• Ignoring or incorrectly evaluating available information
• Depending on only one source of information
• Forgetting to note depths and hazards
• Using impaired or poor judgment



Download Boating Tip #4: Anchoring (PDF format, 32KB)

Anchoring –– Primary Bow Anchor

• Look around, explore the harbor, note depths, wind direction, current, obstructions
• Furl the headsail
• Reverse then stop the boat, shift into neutral, and point into the wind
• Turn the windlass battery dial to the “on” position
• Move to the foredeck and untie the keeper line securing the anchor
• When directed, press the windlass switch to lower the anchor
• Kick the bow roller to release the anchor, if necessary
• Lower the anchor until it hits bottom. Note the depth.
• Snag the chain and make fast using the pipe and windlass brake if necessary
• Back down very slowly and let the anchor dig in and set
• Check that the line is set – the anchor line will be taut and the boat will face into the wind
• Let out chain slowly and count until scope is at least 3 – 5 times the depth of the water
• Brake the slack anchor rode
• Test hold by putting the engine into reverse
• Attach the snubber line – attach the hook to the bottom of a chain link and let out 15′ of line
• Cleat the snubber line
• Take bearings from shore, record and monitor drag
• Set the anchor drift alarm on the chart plotter
• Turn on the anchor light if after dusk

Anchoring –– Secondary Stern Anchor

• Place the stern anchor in the port stern roller
• Flake the chain and line on the port side of the boat
• Attach the bitter end of the anchor line to the toe rail
• After the primary bow anchor is set, slowly motor in reverse to the desired location
• When directed, lower the anchor overboard
• Feed out chain until the anchor hits bottom
• Put the chain on the stern roller and close the pin
• Snag and make fast
• Motor forward slowly while using the windlass to retrieve some bow chain
• Tie off the stern anchor line to a cleat

Retrieving the Stern Anchor

• Release the windlass brake
• Let out the bow anchor chain and back up toward the stern anchor
• Pull up the stern line and chain while backing up slowly, being very careful not to run over the line or chain
• When directly over the stern anchor, lock the windlass brake
• Loosen the anchor, and announce “anchor’s aweigh” when free of the bottom
• Dip the anchor to remove debris before bringing aboard
• Secure the anchor, or bring aboard and stow in the stern lazarette

Retrieving the Bow Anchor

• Start the engine, point toward the anchor, and rev the motor
• Make sure the windlass brake is locked
• Push down on the windlass button with your foot to engage the windlass
• Guide the chain into the anchor locker to prevent tangles
• Remove the hook and snubber line and retrieve
• Motor very slowly in the direction of the anchor while using the windlass to bring the anchor chain aboard
• When the anchor is directly below the bow, slow the windlass
• Loosen the anchor, and announce “anchor’s aweigh” when free of the bottom
• Bring the anchor up into the bow roller
• Rinse the anchor to remove debris
• Reattach the keeper line

Download Boating Tip #3: Mayday & Other Distress Calls (PDF format, 33KB)

Mayday

• Don’t send a “mayday” distress call unless it is a life and death situation or unless you are in imminent danger
• Switch the VHF to high power
• Tune to Channel 16
• Press the alarm signal for 30 seconds
• Press the button and say “Mayday, Mayday, Mayday”
• This is the sailing yacht ___________ – repeat the vessel name 3 times
• Say “Mayday: (vessel name) ____________”
• Our location is _____ (give latitude and longitude, distance from a well-known landmark, course, speed, destination)
• We are (nature of distress)
• We require (nature of assistance)
• We have _____ persons on board
• The injured person is (condition)
• We are a _____ – foot, ____________ (make) ____________ (model), ____________ (length), ____________ (type of boat)
• Our hull color is ____________ with a ____________ stripe
• Our sail color is ____________
• I will be listening on Channel 16. This is ____________ (vessel name)
• Say “Over”, and take your finger off the button
• Listen for a response
• Repeat as many times as necessary until someone responds

Pan

• Pronounced “pahn”
• If you need medical assistance, but not medical evacuation, start your distress call on channel 16 by saying “Pan, Pan, Pan”
• This is the sailing yacht ____________ –– repeat the vessel name 3 times
• Say “Pan: : (vessel name) ____________”
• Our location is _____ (give latitude and longitude, distance from a well-known landmark, course, speed, destination)
• We require (nature of assistance)
• We have _____ persons on board
• The injured person is (condition)
• We are a _____ – foot, ____________ (make), ____________ (model), ____________ (length), ____________ (type of boat)
• Our hull color is ____________ with a ____________ stripe
• Our sail color is ____________
• I will be listening on Channel 16. This is ____________ (vessel name)
• Say “Over”, and take your finger off the button
• Listen for a response
• Repeat as many times as necessary until someone responds

Private Towing Companies

• If it is not an emergency, but you need assistance, call a private towing company instead of the U.S. Coast Guard
• You can call the towing company on the cell phone or use the VHF radio channel 16

  Vessel Assist (800) 391-4869
  Sea Tow (888) 473-2869

• Private towing companies are like AAA for boaters. You join annually for a reasonable fee and are covered while aboard your boat or someone else’s vessel.
• Start a VHF call on channel 16 and say, for example, “Vessel Assist, Vessel Assist, Vessel Assist (nearest location), this is MERMAID, MERMAID, MERMAID calling on channel 16
• The Vessel Assist dispatcher will answer and ask you if it is an emergency, ask you to identify yourself, then will most likely tell you to move to a working channel (probably 68, 69, 71, 72, or 78A)
• Go to the VHF channel as directed and again identify yourself
• Explain why you need assistance and answer any questions asked by the dispatcher
• Provide your Vessel Assist number

Distress Signals

• Shoot red shells into the air using the flare gun. Do not point the gun at anyone. Aim down wind and away from the boat when shooting.
• Fog horn (manual)
• Horn on the VHF
• Hoist the orange distress flag with black ball and square
• Wave your arms up and down
• Hail the other vessel on the VHF radio
• Light a hand held flare or orange smoke. Hold the flare over the water on the lee side of the boat.

Download Boating Tip #2: Nautical Conversion Factors (PDF format, 60KB)

Visibility

Distance to the horizon in nautical miles = 1.17 x (square root of your eye height)
Distance at which an object becomes visible
1.17 x (square root of your eye height) + 1.17 x (square root of the height of the object)

Atmospheric Pressure

Atmospheric pressure at sea level = 14.7 psi For each foot of water depth, pressure increases 0.445 psi Pressure doubles every 33 feet
Example:
Calculate pressure at a depth of 66′
66′ x 0.445 psi / ft = 29.37 + 14.7 = 44.1 = 3 atmospheres

For each 1,000 feet in altitude, pressure decreases 1 foot of head or 0.433 psi, so at 2,000 feet above sea level, pressure would be 14.7 – 2 x 0.433 = 13.83

Barometric pressure

Average at sea level: 29.92 inches = 1013.2 millibars (range 950 mb – 1035 mb)
Inches of mercury x 33.86 = Millibars
Millibar / 33.86 = Inches of mercury

Length

Statute mile = 5,280 feet
Nautical mile = 6,076 feet, 1 minute of latitude, 1/60 degree, 880 fathoms, 7.5 cables
League varies, but in U.S., Great Britain, France and Spain, 1 league = 6,075 yards, 18,225 feet, 5,555 meters, 3 nautical miles

Fathom = 6 feet, 1.83 meters

Meter = 3.281 feet, 0.547 fathoms

Cable = 120 fathoms, 720 feet

Speed conversion formulas

Nautical miles per hour (Knots) x 1.151 = Statute miles per hour
Statute miles per hour x 0.869 = Knots

Nautical miles per hour (Knots) x 1.852 = Kilometers per hour
Kilometers per hour x 0.540 = Nautical miles per hour (Knots)

Statute miles per hour x 1.609 = Kilometers per hour
Kilometers per hour x 0.621 = Statute miles per hour

Nautical miles per hour (Knots) x 1.687 = Feet per second
Feet per second x 0.5925 = Nautical miles per hour (Knots)

Statute miles per hour x 1.467 = Feet per second
Feet per second x 0.682 = Statute miles per hour

Distance / Speed / Time Conversions

Distance = Speed x Time
Speed = Distance / Time
Time = Distance / Speed

60 D ST

Distance in knots
Speed in nautical miles per hour
Time in minutes

Speed = (60 x Distance) / Time
Distance = (Speed x Time) / 60
Time = (60 x Distance) / Speed

Temperature Conversion

Fahrenheit to Celsius (F° – 32) / 1.8 or F° – 32 x 5/9
Celsius to Fahrenheit (C° x 1.8) + 32 or C° x 9/5 + 32

Time

Day = 24 hours, 1,440 minutes, and 86,400 seconds

Time zones were standardized in 1883, with the prime meridian set at Greenwich, England. The earth was divided into 24 international time zones at each 15° of longitude. Each zone is one hour apart. Zones are sometimes altered due to geographic and political boundaries. Some states have modified their time zone boundaries, for example, Alaska, Texas, Michigan, Florida, and Indiana. Some countries, like China, have chosen to use only one time zone.

Time zones W of the prime meridian are “earlier” than Greenwich Mean Time (GMT). Greenwich Mean Time is also referred to as Universal Time (UTC). Times zones E of the prime meridian are “later” than GMT.

The International Date Line is an imaginary line directly opposite Greenwich at 180°. When traveling west, advance one day when you cross the International Date Line.

Daylight Savings Time is applied in many parts of the world to add an additional hour of daylight during parts of the year. Most countries observe Daylight Savings Time during their Summer months, but a few countries add an extra hour during their Winter months instead. In the U.S., Arizona, Hawaii and parts of Indiana do not observe Daylight Savings Time. In most of the United States, remember to:

Spring forward 1 hour the first Sunday in April
Fall back 1 hour the last Sunday in October

Note: There is no “J” or Juliet time zone. J is used to describe the current time for the observer.

Resistance to Capsizing Formula

Divide the boat’s gross tonnage in pounds by the constant 64, then take the cubed root of that number.
Divide the beam of the boat in feet and tenths of a foot by the number derived above.
If the result is less than 2, the boat is relatively safe from capsize

Example:
Boat displaces 13 Gross Tons = 26,000 pounds
26,000 pounds / 64 = 406.25
Cube root of 406.25 = 7.406
Beam = 12′ 11″ = 12.916′
12.916′ / 7.406 = 1.74
1.74 is < 2

Boat Displacement : Length Ratio Formula

Divide the LWL by 100, then cube the result
Divide the resulting number by the boat’s displacement in gross tons

Example:
34.9′ / 100 = 0.349
(0.349)3 = 0.0425
13 Gross Tons / 0.0425 = 305.9

> 380 Very heavy displacement boat
320 – 380 Heavy displacement boat
250 – 320 Medium displacement boat
120 – 250 Light displacement boat
50 – 120 Very light displacement boat
< 50 Ultra light displacement boat

Maximum Hull Speed

1.34 x the square root of the LWL (waterline length)

Larger displacement sailboats can usually travel faster than smaller boats because hull speed depends on the length of the boat’s waterline and the volume of water displaced. Resistance increases as speed increases. At optimum speed the bow and stern wakes combine to form a single wake or wave. Theoretically, a sailboat cannot travel faster than the wave created, and wave speed is 1.34 times the square root of the distance between wave crests. Wave length increases proportionally to wave height. So the higher the wave created, the greater the distance between crests, the faster the wave travels. As sailboat speed increases, a greater volume of water has to be displaced, the bow wave increases in height, the distance between crests increases, and boat speed increases. It is only possible to exceed hull speed, if the sailboat, because of its design (some fin keel and centerboard designs), is capable of planing along the water surface, or by sailing downwind and surfing down the front of a wave.

Beaufort Scale for Measuring Wind Speed