Introduction to Navigation Part 5 Understanding Latitude and Longitude

Finding a street address on earth is not a difficult task, however finding a specific location in the middle of the ocean can present the mariner with a few problems.  In order to locate a specific location anywhere on earth, a grid system has been developed to give each area on the earth a specific address.  This system deals with “parallels of latitude” and “meridians of longitude.”

In order to begin to understand how to navigate, the navigator must understand some basic terminology and how it relates to the grid system.

These basics are covered in the online Nautical Know How Basic Boating Safety Course at http://boatsafe.com/navigation . It is highly recommended that, prior to beginning this advanced Coastal Navigation Course, each student successfully complete the Basic Boating Safety Course.

 A “great circle” is a circle formed on a sphere, such as the earth, by the intersection of a plane passing through the center of the sphere.  An arc of a great circle is the shortest distance between two points, hence a great circle route is the shortest route between two points on the earth.  You might think of splitting an orange down the middle and going through the center.  The plane exposed would represent a great circle.

 A “small circle” is a circle formed on a sphere, such as the earth, where the intersection of a plane does not pass through the center of the sphere.  Cut that same orange in any other manner that does not pass through the center and you have created a small circle.

Parallels of Latitude are small circles that are measured from the equator (the only latitude that is a great circle) beginning at O° latitude at the equator to 90° North and South at the Poles.  These parallels are equal distance apart and run horizontally across a chart, like the rungs on a ladder.  You can use the “ladder” analogy to remember that “laddertude” lines are drawn across the chart, not up and down. 

Because latitude lines are equal distance apart they can be used to measure distance on the surface of the earth.  The only parallel of latitude that is a “great circle” is the equator itself as shown in the graphic. You will find latitude measurements on the side of your nautical chart.

Meridians of Longitude are “great circles” that pass through the north and south geographic poles.  The meridian of longitude that cuts through the earth at Greenwich, England is labeled as O° longitude and is known as the prime meridian.  Longitude is then measured from O° at Greenwich to 180° West and 180° East of Greenwich. The 180°th of longitude is the International Dateline.

Related Posts:

http://boatsafe.wordpress.com/2011/05/17/introduction-to-navigation-part-4-getting-to-know-your-magnetic-compass/

http://boatsafe.wordpress.com/2011/05/16/introduction-to-navigation-part-3-definitions/

http://boatsafe.wordpress.com/2011/05/13/introduction-to-navigation-part-2-nautical-charts/

http://boatsafe.wordpress.com/2011/05/12/introduction-to-navigation/

Introduction to Navigation Part 4 Getting to Know Your Magnetic Compass

You may have noticed, if you have looked at a nautical chart, that there were two rings on the compass rose. The outside ring is based on true north and the 000° direction points to the true North Pole. On the inside ring labeled “MAGNETIC” the  000° direction points in a different direction than the outside ring.

These basics are covered in the online Nautical Know How Basic Boating Safety Course at http://boatsafe.com/navigation .

The difference between True and Magnetic is called “Variation.” Variation is a naturally occurring disturbance caused by the magnetic north pole. Variation will change depending on where you are located on the earth. If you are operating on the West Coast of the US you will have east variation because the magnetic north pole is located east of you. On the East Coast of the US you have west variation because the magnetic north pole is west of your location.

Another error which may show up in your magnetic compass is called “Deviation.”  Magnetic compasses are also affected by magnetic fields on the vessel itself. Just put some sort of ferrous metal such as a screw driver next to your compass and you will see an example of this error.

Significant errors of deviation could be caused by metal tanks, your engine, metallic objects near your compass or even electromagnetic interference caused by your radio.

To safely and accurately navigate from one position to another it is important to be able to correct for both “variation” and “deviation”  and be able to steer a course by your magnetic compass.

If you want to learn more about the magnetic compass and how to calculate TVMDC…READ MORE.

Introduction to Navigation Part 3 Definitions

The following navigation terms are used in most recognized navigational texts. Learning and understanding what they mean will give you a head start on the information that is to be presented in later chapters. Don’t worry about memorizing all these at this time. You will get plenty of exposure to these terms as you advance through the course.

These basics are covered in the online Nautical Know How Coastal Navigation  Course at http://boatsafe.com/navigation .

Piloting is defined as the determination of the position and the direction of the movements of a vessel. This involves frequent or continuous reference to landmarks, aids to navigation, and depth sounding.

Direction is the orientation of an imaginary line joining one point to another without regard to the distance between them. Direction is measured in angular units of arc, measured in degrees, from a common reference whether it be true north or magnetic north. The usual reference is true north. The division of the degree may be either minutes and seconds or decimal fractions. Direction is written with three digits as in 000°.

Distance is the separation between two points without regard to direction. In navigation it is measured by the length of a line on the surface of the earth from one point to the other. It may be measured in units of yards, nautical miles or kilometers. The nautical mile is commonly used by navigators. The international nautical mile is 6076.12 feet. This is approximately 1.15 longer than the statute mile used on land.

Time is written as four digits in a 24 hour system; four minutes after midnight is 0004, 9:32 AM would be written as 0932 and 1:16 PM would be written as 1316.

Speed is defined as the rate of movement, and in navigation is usually measured in nautical miles per hour, or knots. The time element is included in the definition of “knot”; the use of knots (kts) per hour is incorrect. Speed is represented on your chart as “S”. Example S = 7.5 kts.

Dead Reckoning (DR) is the projection of a present position to an anticipated future position. This is done by using a previous known position and applying known direction, speed and distance covered. The term comes from deduced reckoning which was abbreviated ded reckoning. DR plots are done at a minimum of every hour or when ever you change course or speed. A new DR plot line is started each time a new “known position” is found.

Course is the direction of travel through the water or the direction a vessel is to be steered or is being steered. The course may be designated as true (T), magnetic (M), or compass (C). Course is always written in three digits and is followed by the abbreviation of its source. Example C = 090° T

Bearing is the direction of any place or object from a given point. It may be designated as true (T), magnetic (M), compass (C) or relative (R). It is always written in three digits and is followed by the abbreviation of its source. Example B = 270° T

Heading is the direction the vessel points or heads at any instant as read from your compass. It is always written in three digits. Example HDG = 270°

Fix is a known location at a specific time based on verifiable information and carrying a high degree of accuracy. Example:  0900

Running Fix is a known location at a specific time, with a lesser degree of accuracy than a fix. It is based on information obtained from a single event at two different times and plotted as a common time. Example:  R Fix 0900

Electronic Fix is a fix obtained from one or more electronic devices. Example:  0900

Introduction to Navigation Part 2 Nautical Charts

Today is the second of a series of articles about Navigation. You can advance your Navigation Know How by participating in the Nautical Know How Coastal Navigation Course.

These basics are covered in the online Nautical Know How Basic Boating Safety Course at http://boatsafe.com/navigation . It is highly recommended that, prior to beginning this advanced Coastal Navigation Course, each student successfully complete the Basic Boating Safety Course.

Nautical charts are different from maps in that they specifically depict water areas while maps concentrate on land area, roads, landmarks, etc. Land areas and features on charts are sketchy and are noted only for their interest to the Navigator. Unlike maps, the nautical chart conveys much information specifically designed to assist in safely navigating the area that the chart covers.

Chart Scaling

 The scale of a chart is expressed as a ratio such as 1:80,000. This could also be represented as the fraction 1/80,000. This means that one unit on the chart represents 80,000 of the same units on the earth. The terms “small scale” and “large scale” can be confusing if you haven’t studied fractions recently. The denominator of the fraction (the number under the line) is the number that changes as the scale of the chart changes. The larger the denominator  the smaller the fraction. For instance 1:80,000 is smaller than 1:40,000, so the larger the denominator the smaller the scale of the chart. That is, a 1:80,000 chart would be a small scale while a 1:40,000 would be a large scale.

 Chart Colors

The major water areas are not colored and retain the white color of the paper itself. Shallow water areas, shown in light blue and light green, indicate shallows that are uncovered at some stage of the tide, such as marsh areas.

 Small objects such as buoys and markers are shown in a magenta color. Because charts are used at night under red light (to keep from impairing night vision) the color magenta shows up best at night and in the day.

 Buoys and dayboards that are actually red are indicated in magenta. Green buoys and dayboards are shown in green.

Lighted buoys, regardless of their color, are shown with a magenta dot over the small circle portion of the chart symbol. Cautions, symbols noting danger, compass roses and recommended courses are also noted in magenta.

For more about the Nautical Know How Coastal Navigation Course…READ MORE.

Introduction to Navigation

Today starts a series of articles about Navigation. We will give you a list of skill sets required to become a “real” navigator and also give you the opportunity to advance your Navigation Know How by participating in the Nautical Know How Coastal Navigation Course. This course will give you step-by-step instructions on how to navigate safely from one point to another. It teaches you to take into consideration all effects including set, drift, tides, currents, etc. that might hinder you along the way.

These basics are covered in the online Nautical Know How Basic Boating Safety Course at http://boatsafe.com/navigation . It is highly recommended that, prior to beginning this advanced Coastal Navigation Course, each student successfully complete the Basic Boating Safety Course.

Navigation can be divided into four primary classifications:

• piloting
• dead reckoning
• electronic navigation
• celestial navigation

The problems that you, as a navigator, must solve are as follows:

1. How to determine your position.
2. How to determine the direction in which to proceed to get from one position to another.
3. How to determine distance and related factors of time and speed as you proceed.

Of these three problems facing every navigator, the most basic is that of locating your position. Unless you know your position, you cannot direct the movements of your vessel with any accuracy, safety or efficiency.

You will need to have, and learn to use, several navigation tools. Although there are many tools at your disposal at any marine store, the following are the minimum necessary:

•  dividers
• parallel rulers
• right angle triangle (optional, but handy)
• charts
• pencils
• hand bearing compass
• steering compass
• watch or chronometer
• log and time-keeping note paper
• calculator, abacus or fingers & toes

One Last Reminder – Is the Drain Plug In?

Invasive species regulations are now in effect in many states and many of them now require boaters to remove the plug and drain the bilge and live well before transporting a watercraft. In our Basic Boating Safety Course we have an extensive section on trailering and one of the things we emphasize is to make sure the drain plug is in before launching your boat.

The majority of recreational boats in the United States are trailered to and from the water. Your boat trailer is only one part of the entire boating package, which includes the boat, trailer, hitch and towing vehicle. Neglecting the trailer’s maintenance can result in damage to your boat, your towing vehicle or both. Below is our check-list for launching.

Launching

1. Do initial launch preparations away from the ramp so as not to impede launching for others.
2. Raise the outdrive or motor, remove the support bracket and install the drain plug.
3. Disconnect the trailer wiring. Remove tie down straps and again check the drain plug.
4. Make any equipment adjustments necessary and check the drain plug.
5. Connect the fuel tank, check fluid levels and check the drain plug.
6. Drive to the ramp and back the boat and trailer down the ramp, keeping the tow vehicle’s wheels out of the water.
7. Set the emergency brake, shift into Park, and block the wheels.
8. Someone should get aboard the boat, turn on the blower, lower the motor, look for water entering the boat, (in case you forgot to check the drain plug) sniff the bilge and start the motor.
9. Make sure you have attached a bow line to the boat, then release the winch and disconnect the winch line.
10. You should be able to launch the boat with a slight shove or by backing the boat off the trailer under power.
11. Return the towing vehicle to the parking lot as soon as the boat is launched so the next person in line may proceed.
12. Move the boat to an area away from the ramp to load additional equipment and passengers.

Why Do So Many Boats Sink in the Spring?

We recently published a pre-season check list to assist in dewinterizing our boat for the upcoming boating season. According to BoatUS insurance division there are five things that are often overlooked that can result in you boats first trip being one that isn’t on the water but under the water.

The Top Five Reasons Why Boats Sink in the Springtime:

1. Missing or damaged hose clamps: These clamps are often removed in the fall to winterize the engine, and then forgotten about in the spring when the boat is launched. Tight spaces in engine compartments make it difficult to see some unsecured or deteriorated clamps.
2. Unsecured engine hoses: Over the winter, freezing water can lift hoses off seacocks (valves).
3. Spring rains: Combine heavy rains with leaking ports, deck hatches, cracked or improperly caulked fittings, chain plates and even scuppers clogged by leaves and your boat could be on the bottom soon. 
4. Broken sea strainer: Glass, plastic and even bronze strainer bowls can be cracked or bent over in the winter if not properly winterized, allowing to water trickle in when the seawater intake seacock is in the open position.
5. Leaking stuffing box: If equipped, a steady drip from an improperly adjusted stuffing box (the “packing” around the prop shaft) has been known to swamp a boat.   

Understanding The Danger of Propeller Strikes

As “boating season” and the thoughts of getting out on the water start to increace. I thought it appropriate to to remind all boaters of the danger of propeller strikes.

Did you know?

• A typical three-blade propeller running at 3,200 rpm can inflict 160 impacts in one second.
• A typical recreational propeller can travel from head to toe on an average person in less than one tenth of a second.
• Most propeller accidents CAN be prevented!

What Can You Do?

1. Wear your engine cut-off switch lanyard and your life jacket at ALL times. If the lanyard is removed from the switch, the engine will shut off.
2. Assign a passenger to keep watch around the propeller area of your boat when people are in the water.
3. Consider purchasing propeller safety devices for your boat.

Safety Tips

• Before starting your engine, walk to the stern and look in the water to make certain there is no one near your propeller (people near the propeller may not be visible from the helm).
• Never allow passengers to board or exit your boat from the water when engine(s) are running – even at idle and in neutral your propeller may continue to spin.
• Educate passengers about the location and danger of the propeller(s).
• Call attention to and discuss any propeller waning labels around your boat.
• Be especially alert when operating in congested areas and never enter swimming zones.
• Take extra precautions near boats that are towing skiers or tubers.
• Never permit passengers to ride on the bow, gunwale, transom, seat backs, or other locations where they might fall overboard.
• Children should be watched carefully while onboard.
• Establish clear rules for swim platform use, boarding ladders, and seating (if possible, passengers should remain seated at all times).
• If someone falls overboard, STOP! Then slowly turn the boat around, and keep the person in sight as you approach. Assign a passenger to continuously monitor the person in ;the water. Turn your engine off FIRST and then bring the person to safety.
• NEVER reverse your boat to pick someone up out of the water. If necessary, go around again.

Safety Devices

A variety of safety devices are available to help prevent propeller strikes:

• Wireless cut off switches
• Propeller guards
• Ringed propellers
• Propulsion alternatives (jet drive)
• Interlocks
• Sensors
• Anti-feedback steering

Super-Fast 22-foot HeliCat Coming to Newport Show

This year’s Newport Boat Show, April 18-21, will feature the debut of a truly unique vessel: the HeliCat. This new 22-foot high-speed catamaran can travel 20-30 mph in conditions as rough as whitecap waves while getting an astonishing 5 mpg fuel economy: a feat that is not possible in other boats.            

It is built as a two-seater, fore and aft like a motorcycle, and it gives that same open-air feeling of exhilaration. But there’s no road traffic to maneuver around when you’re driving a HeliCat.              

“The boat rides like it’s on a rail,” said Sandy Williamson, owner of HeliCat LLC. “It can turn sharp at very high speeds — and is very fun.”            

Those who need a fast, safe and dependable form of water transportation will appreciate the HeliCat’s low maintenance requirements and excellent fuel economy, Williamson said. And with watertight compartments and foam floatation in each hull, the boat is described as virtually unsinkable.            

It weighs less than 2,500 pounds and can be towed by almost any car, with an aluminum trailer that was specifically built for the HeliCat.            

While the prototypes were from Argentina, new HeliCats will be built by Sunbacker Fiberglass in Monroe, Wash.            

Not only are they fun to ride, if you have a business to promote, the HeliCat just might be an ideal way to do it, Williamson said. “You can wrap it with your company contact info, logo and photos for eye-catching and fun advertising, both on and off the water.”

For more details, visit helicat.net — and to see the HeliCat for yourself, visit the Newport Boat Show.

Spring is here, Coast Guard urges Safe Boating

BOSTON — In light of spring temperatures, the Coast Guard emphasizes safety for recreational boaters and paddlers planning to venture out on the inland and coastal waters of the Northeast this spring.

The rescues of two kayakers on Sunday by Coast Guard crews and additional first responders serve as reminders that boating season in the Northeast is just around the corner and all boaters should practice maritime safety measures while out on the water.

“The warmer weather can create a false sense of security,” said Walt Taylor, Recreational Boating Safety Manager for the 1st Coast Guard District. “Though the air is warm, the water is still very cold, and in the event of a capsize hypothermia can quickly set in.”

Some safe boating tips to remember are:

• Dress for the water temperature. Though the air may be warm, the water is still cold. Wet suits and dry suits offer protection against hyperthermia in the event of a capsize or immersion in the water.
• Check all required safety equipment to be sure it is in good working order. The Coast Guard Auxiliary provides free vessel safety exams. Contact your nearest flotilla for more information.
• File a float plan before getting underway.
• Be sure to have U.S. Coast Guard approved lifejackets aboard. All boaters and paddlers are encouraged to wear their lifejackets while underway.

More information can be found at the Coast Guard Boating Safety Resource Center.