In this lesson you will learn about:

• Air masses 
• Clouds
• Weather fronts
• High's and Low's
• Cyclones and Depressions
• Sea and Land breezes
• Various types of Fogs

Before you proceed to sea and while you are at sea, it is highly important to stay informed regarding the current and imminent weather conditions. The latest weather information is crucial for the safety of the crew and the vessel. Severe weather can be avoided, and the risk of injury and damage can be reduced. Weather forecasts should be obtained at regular intervals. Let’s have a look at various sources of weather information. Before you go to sea, you can obtain weather information from newspapers, TV and the Internet.

In former times, before wind measuring equipment was available,

the Beaufort Scale was the only device available to determine the wind force.

The  scale was invented in the year 1805 by Sir Francis Beaufort and officially adopted in 1838.

Sir Francis Beaufort sailed for many years in the British Royal Navy as a Commander. The first Beaufort Scale was originally related to tall ships and their sails. Later on it was modified to imply the effects of wind on land and sea.

Weather faxes provide the latest meteorological and oceanographic information available worldwide. They can be received with a Single Sideband Radio. 

The following key weather and sea charts are useful to mariners:

· Surface charts

· Sea state analysis

· Wind and Wave charts

· Sea surface temperatures

· Satellite imagery and · Ice charts

The weight of air pressing down on the earth is called the air pressure.

Air pressure is caused by the earth’s gravity, which acts like a downward force.

Pressure can be measured by a barometer and can be recorded by a barograph.

Pressure readings can be used to predict: storms,low pressure areas,

high pressure areas,weather fronts,and wind fields.

The barometer is the most useful weather forecasting tool for small vessels. There are two types of barometers, mercury and aneroid.

Navigation basics. We presume that the earth is a perfect sphere and is the center of the universe.

The earth is rotating round a hypothetical axis N and S  and is penetrated in two points. 

The upper point "N", is called the North Pole and the lower point "S", is called the South Pole. 

"N" and "S" are known as the Geographical poles. 

"C" is the center of the earth known as the core

Any plane passing through the center "C" is known as a Great Circle Plane.

The circumference of the great circle that is right angled to the hypothetical axis "N and S " is called the Equator,

This divides the globe or sphere into two equal hemispheres, the northern hemisphere where the North Pole is located,

and the southern hemisphere where the South Pole is located. The circumference of the small circle "A A1" with a plane parallel to the Equator, is called the Parallel of Latitude.

In this lesson we will learn about Nautical Charts.

A Nautical Chart is a graphic representation of the marine environment and is essential for safe navigation. The Mariner uses the Nautical Chart to navigate and as a worksheet.

Using the Chart, the mariner lays out courses  and navigates the ship safely by the shortest and most economical route.

On a Nautical Chart we can observe: 

the Latitude and Longitude scale.

the form and nature of the coast, 

the depths of the water and composition of the sea bed,

locations of dangers to navigation,

we can also see locations of man-made aids to navigation,

the characteristics of the Earth's magnetism,

Tidal information and much more. We will study all of these individually.

The Parallel ruler is used to draw lines and plot directions on a nautical chart. In addition, it allows courses to be measured from a convenient meridian. The ruler is split in half and the two halves are joined together by pivot points with aluminum arms and handles. Usually they are made of extra strong, crystal clear acrylic.

In this lesson you will learn about Variation and Deviation

On every nautical chart there is at least one Compass Rose.

The Compass Rose consists of the following: the outer rose, which is aligned with the True North and the inner rose, which is aligned to Magnetic North. 

Near the center of the Compass Rose we can read the local variation, the year that the variation was observed and the annual rate of change.  When we are shaping a course or plotting a position we need to convert between True and Magnetic.

When we are on an open sea passage out of sight of land, at night or in a dense fog, we must be able to keep an accurate track of our position and course at all times.

There are many ways we can do this, and many techniques we can use for finding our position. The most basic technique is called the Dead-Reckoning Technique.

The major concern of the navigator while navigating near the coast or off-shore,  is to determine his position as accurately as possible.

So far, you have learned about the Dead Reckoning and the Estimated Position. In this lesson you will learn about Line of Position, LOP  Running Fix position and Fix position. You will also learn about electronic fixes, fixes containing a mixture of position lines and ranges by dipping distances.

All vessels need a passage plan
What is a passage plan and how do you create one.
A passage plan helps to bring the vessel and the crew safely from berth to berth.
Durring your voyage you may experience rough weather, fog, strong tides etc.
Therefore you should have a contigency plan, your passage plan, ready before you start your voyage.

Make sure that you carry at least two anchors, one as an everyday anchor that is stowed at the bow in the anchor locker, and one as a storm anchor.

The characteristics of the boat and the type of sea bed - sand, shale, mud, gravel - affect the type of anchor you should use.

Commonly available anchors are:

The Plough type anchor, which provides very high holding power by digging itself into sea bed sediments.

The plough type is also effective on weedy sea beds.

The Fluke type anchor, which provides very good holding power by burying itself into sea beds of sand or mud, but not so good in rocks or kelp.

It is lightweight and can be stowed flat, but can be difficult to remove from mud.

The Fisherman - type anchor, which has diamond-shaped flukes that makes the anchor function efficiently as a "rock pick". It must be large and heavy to be most effective and can penetrate and hold in weeds, gravel, or rocks. It folds flat for stowage.

Fire prevention is the best way to fight a fire.  

Therefore it is important to know what may cause a fire, and where it could start.

The most common areas where fires originate are the galley, the electrical panels and the engine room. Possible causes are: electrical faults, cabin heaters, electric motors, or an explosion in the gas  or fuel supply.

How do you choose the correct buoyancy device for you and your crew? 

First consider your cruising area. 

Buoyancy aids and lifejackets can either be equipped with inherent foam buoyancy, inflatable buoyancy or a combination of both.

A jacket with inflatable buoyancy can be filled by mouth or with gas bottles. The gas bottles can be activated automatically, on entering the water or manually when required.

Distress signals are used when a boat or a crew member are in grave and immenent danger and require immediate assistance.

Several devices can be used to attract the attention of possible rescue units: a radio, an EPIRB, a radar transponder, pyrotechnics, flags, and signals. Which device is the best to use depends on the circumstances. If the visibility is good and the rescuers are close by, you could use hand flares, or if you are far away from land maybe it is best to activate the EPIRB.

Life rafts are constructed in various sizes and shapes.

They are usually made of rubber or PVC.

The life raft should be stored either in a neoprene or canvas valise or in a glass fiber container.

Life rafts should be approved, such as by SOLAS (Safety of Life at Sea) or ORC (Ocean Racing Conference). 

Here are some key features to look for in selecting a life raft: 

The life raft should be equipped with water ballast pockets.

When the raft is deployed, these pockets will fill with water and reduce the risk of capsizing.

Make sure that the floor is inflatable or at least double layered. 

Double and inflatable floors provide additional thermal protection, and reduce the risk of hypothermia.

The buoyancy chambers should have two separate buoyancy compartments.  If one buoyancy compartment is punctured or torn, the other compartment can support the full weight of the number of people the raft was designed for.

Helicopters are frequently used for Search and Rescue operations. 

It is important that you strictly follow the instruction of the helicopter crew, as they know when and how a rescue is safely and efficiently performed.

To facilitate the rescue operation, some vital preparations can be carried out before the arrival of the helicopter. If you are still in the boat, try to keep a heading of 35 to 45 degrees off the wind. 

In case no motor power is available you can slowly drift down by streaming the sea anchor from the bow or by lowering the anchor and chain. In both cases, have your sails lowered, so that the helicopter will not be entangled in your gear.

Navigation lights are used to prevent collisions at night or in times of reduced visibility.

Vessels are required to show the proper navigation lights from sunset to sunrise in all weather conditions and in conditions of reduced visibility.

All vessels must display basic navigation lights. These lights indicate:

- Whether a vessel is under sail or power.

- The direction of the vessel.

- The likely size.

- The activity. Additional specific sets of lights are used by vessels to indicate that they are engaged in a specific job or that they are under restrictions.

The primary cause of restricted visibility is fog, heavy rain, or

very rough seas. Haze or snow can also cause visibility to be restricted.

Sailing in restricted visibility presents hazards, such as collision with another vessel or object, and navigational errors, such as getting off course and running aground. 

Fog is quite difficult to predict and is likely to take you by surprise.  Still, there are some warning signs that can help you to predict fog is coming; for example, a fogbank on the horizon, cold and moist air, general mistiness and progressively reduced visibility as the fog approaches, also misty and diffused navigation lights at night.

Start sounding your foghorn. 

Sailing vessels must sound one prolonged blast plus two short blasts every two minutes.

Turn on your navigation lights.

Rig up the radar reflector as high as possible if one is not permanently fitted. Remember, the big ships are more likely to maintain their speed, relying on their radar to detect other ships. 

If the sea is rough, they probably won’t detect you, since the echoes from the waves cover the small echo from your sailing boat 

Make sure that all crew wear their life jackets and that the life raft is clear and ready to use. In addition, have some red and white flares handy.

Tides are the vertical rise and fall of the surface of a body of water, caused primarily by the gravitational attraction of the moon and to a lesser extent, the sun. 

The rotation of the earth is the primary cause of two high tides and two low tides per day, also called semidiurnal tide, experienced in most parts of the world. 

Some locations on earth have only one high tide and one low tide per day - called diurnal tide - due to the path of the moon and other geographical factors.

A few other places experience a combination of diurnal and semidiurnal tides, called mixed tides. 

The difference in height between a high tide going to a low tide, or a low tide going to a high tide is called the tidal range.  The rising tide is called the flood tide and the falling tide is called the ebb tide.

Let’s have a closer look at "Tidal Heights" and "Chart Datum". 

On nautical charts, soundings and drying heights are measured from Chart Datum. 

Chart Datum is the Lowest Astronomical Tide or L A T , meaning the lowest level to which the tide is expected to fall. All depths on a chart are measured below chart datum and all drying heights are measured above it.

Non-drying heights, for example a lighthouse, are always measured above Mean High Water Springs, not Chart Datum, as an added safety margin.

The height of tide is always measured above Chart Datum.

There are two methods of calculating the tidal height. 

The first uses the tide tables, which is a very accurate method, and the second uses the

"Rule of Twelfths", which is not so accurate and should be used with caution!

Let’s now use the tide table to calculate the tide for a standard port. But first, what is a standard port? In the tide table we distinguish between standard ports and secondary ports. A standard port is a port for which the times and heights of high and low water are predicted for every day of the year. A secondary port is a port that has an assigned standard port. The reason for the use of secondary ports is that it is impossible to list the times of high and low of each port in the world. The tidal curves of the secondary port and the assigned standard port are assumed to be the same.

The Tidal Curve is another method of determining times of high and low water. Before you use the curve, note the times and heights of tide for the day from the tide table.

Now let’s see how we calculate the times of high and low water in a secondary port.

The tidal stream is the horizontal flow of water which is caused by the rise and fall of the tide. 

The direction of the tidal stream is called "set" and its speed is called "drift". 

In a harbor we call the tidal stream the flood stream, when the tide is rising, and the ebb stream, when the tide is falling. 

Offshore we use the name in accordance with which direction the tidal stream is flowing towards

e.g. "south going stream" or "the stream is setting 180 degrees".  

A good indication of the set of the stream is given by ships at anchor or moored buoys.   Note that water which is driven mainly by the prevailing winds are called currents.

The Global Maritime Distress and Safety System (GMDSS) was developed by the International Maritime Organization (IMO).  
GMDSS is an internationally recognized distress and radio communication safety system.  
The system uses satellites and digital selective calling technology to provide an automatic means of receiving and transmitting distress alerts.
The GMDSS system is primarily a vessel-to-shore alerting system.  
The Rescue Coordination Centers (RCCs) receive distress alerts from ships and then coordinate the rescue.  
The system also provides a vessel-to-vessel distress-alerting feature.  
Other types of messages that could be transmitted by the system are: urgency, safety and routine communications and safety information broadcasts, e.g. (navigation warnings, weather forecasts and rescue messages).

Radar gets its name from a system of Radio Detection and Ranging.
How does radar work?
Radar transmits short pulses of radio waves that travel outwards, basically in straight lines.
When these waves hit a surface, like a vessel or a buoy, some of the waves are returned.
By measuring the time difference between transmission and reception of a reflected wave, the distance to an object can be calculated.
The direction in which the scanner is pointing when it receives the reflected wave represents the bearing of the object.

The echo sounder is an important and necessary electronic navigation instrument that determines the depth of water under the keel.  
This instrument is one of the prime considerations for safe navigation.
An echo sounder consists of the transducer and the display.  
The transducer transmits ultrasonic waves through the water.  
The wave strikes the seabed and part of the wave are then reflected back and received by the transducer.

The Global Positioning System (GPS) is a satellite - based aid to navigation system placed into orbit by the United States Department of Defense.
The system consists of 24 satellites, orbiting the earth twice a day at an altitude of about 12,000 miles.
GPS satellites are powered by solar energy.
Backup batteries are installed on board to keep them running in case of a solar eclipse.
The system provides highly accurate worldwide positioning and navigation information 24 hours a day.

This lesson you will learn about other GMDSS equipment:

• VHF DSC
• E.P.I.R.B
• NAVTEX
• S.A.R.T.
• INMARSAT