LESSON ONE: PREPARING FOR YOUR JOURNEY
Navigation simply stated is getting from one place to another. The Egyptian nobleman, Harkuf, who lived around 2300 BC, is thought to be the first documented explorer. Stars and migratory birds were used as navigational techniques. Navigators had names for over 200 stars. They knew exactly when the stars rose and fell. Famous explorers such as Columbus, Marco Polo and Magellan used these techniques to navigate around the world. Tools such as a back staff and quadrant have been replaced with the compass and GPS.
Today, we seek goods from all over the world. We are also exploring the realm of the sea. Navigating in a time effective manner is necessary to assist in economic management. Knowing where we are going and how long it will take to get there will also allow rations to be made for crew, fuel, and other supplies. Modern technological advances help us track ships and make educated assumptions as to what might occur while navigating the seas.
During this course, students will track a real ship in real time as it makes its journey from home port to port of call. A possible introduction to the course might include showing students clothing tags from various countries and asking them how they think these goods get from country to country. You could also discuss automobiles, electronics, food, etc.
A Captain's Log is a book in which captains write down the details of their voyages. The captain's log includes details in three areas:
LATITUDE AND LONGITUDE:
Every inch of the Earth, every country, city, and state, any position in the ocean can be located if we know two things, that position's latitude and longitude. If a ship's captain records the ship's position while at sea, these are the coordinates he would use.
Latitude and longitude are measured in degrees, "minutes of arc" and "seconds of arc." These are written using the symbols ( °, ', " ) e.g. 36° 50' 51" translates to 36 degrees, 50 minutes and 51 seconds.
The measurement that tells you how far you are east or west of the Prime Meridian (the thick line in the image below that passes through Greenwich, England and part of Africa) is called longitude. Every longitudinal line crosses the equator. The equator is a circle. Because of this, we can section it into 360 individual degrees. These 360 degrees are the values for longitude.
Starting from the equator, you can measure 90 degrees northward and 90 degrees southward. As an example, Nauticus is at 36 degrees N (north). The South Pole is at 90 degrees S (south), and the North Pole is at 90 degrees N (north). An easy way to remember that latitude is represented by horizontal lines is to think of a ladder. The rungs on a ladder are horizontal so remember ladder-tude.
The measurement that tells you how far you are east or west of the Prime Meridian (the thick line in the image below that passes through Greenwich, England and part of Africa) is called longitude. Every line of longitude must cross the equator. Since the equator is a circle, we can divide it--like any circle--into 360 degrees, and the longitude of a point is then the value of that division where it meets the equator.
From prime meridian, which is located at Greenwich, England, you can measure 180 degrees to the west, 0 to –180 degrees. You can also measure 180 degrees to the east, 0 to 180 degrees. Western degrees are always negative, and eastern degrees are always positive.
Lines of latitude and longitude form an imaginary grid over the entire Earth's surface. We can easily locate places anywhere in the world by looking up that place's latitude and longitude. For example, the location of Nauticus is 36°50'51"N 76°17'53"W.
It's standard practice when writing coordinates to write latitude first, or place it above longitude. You don't need to write out the words latitude and longitude or even abbreviate it. By stating N, S, E or W (the cardinal directions) you are describing where the points are located.
With the invention of GPS (Global Positioning System) it is easy to determine the latitude and longitude of a ship's position.
The Nautical Mile
One nautical mile = one degree of latitude. One degree of latitude is 60 nautical miles from the next. The distance between each degree of longitude is not a constant value because lines of longitude converge, or get closer together, the closer they get to the poles.
A knot, abbreviated kt or kn, is used around the world for maritime and aviation purposes as a measurement of speed.
1 international knot = 1.000 nautical mile/hour = 1.852 Km/h exactly.
In some sailing ships, the ship's speed was determined by tossing a log tied to a rope from the stern of the ship. A knot, or nautical mph (mile per hour), was calculated by counting the knots in the rope. Some sources suggest that knots spaced 47' 3" apart slipped between the fingers of one sailor while another sailor used a sandglass to measure how many knots passed by in 28 seconds. The count would then be recorded and used by the sailing master to assist in the navigation of the ship.
A barometer is an instrument used to measure atmospheric pressure.
Barometers are used to measure atmospheric pressure. High, or increasing air pressure is indicative of fair weather whereas low, or decreasing air pressure is indicative of stormy weather. Meteorologists segregate similar areas of pressure on a weather map into concentric circles called isobars. Isobars make it easier to locate high (H) and low (L) pressure areasmaking it easier to predict the weather. High pressure areas generally divert the course of approaching weather systems. Low pressure areas act like a funnel, pulling in approaching weather systems with the result being an increase in storm activities. When a consecutive series of barometer readings indicate that the pressure is falling, adverse weather, usually involving precipitation of some form is likely. However if consecutive pressure readings indicate that the pressure is rising, the weather will generally be nice with no precipitation.
Dewpoint is the temperature to which air must be cooled, in order for the air to become saturated with moisture that creates dew or fog. A higher dewpoint indicates more moisture present in the air. Understanding how to interpret dewpoint readings is critical to a ship's captain. When the conditions are right, meaning, when the dewpoint and the surface air temperatures approach each other, it is likely that fog will develop. Additional factors such as clear skies and light winds also contribute to fog formation.
Wind barbs indicate both the wind speed in knots (nautical mile per hour) and the wind direction (from which the wind is coming from). Each flag on a wind barb indicates 50 knots, each long segment is 10 knots, and each short segment is 5 knots. To get the wind speed, just add up the flags and segments.
Inform your students that the final project will take the form of a Captain's Log. The students should use this Captain's Log to record any notes, thoughts and ideas they develop during the course of each lesson. They will also complete more formal entries in the Captain's Log in plotting their ship's voyages.
To construct the included Captain's Log, print pages one and two on one sheet of paper front and back, likewise for pages 3 and 4. Fold the two sheets in half and assemble according to the page numbers.
If your budget does not allow the cost of printing the included Captain's Log, students can construct their own with construction paper.Materials
The following pages should be included in the Captain's Log:
LATITUDE AND LONGITUDE LESSON PLANMaterials
WEATHER LESSON PLANMaterials
Ship captain's rely on a variety of information while at sea. One of the most important areas that a captain is interested in is the speed and the direction in which the wind is blowing.
Wind barbs are a convenient way to represent wind speed and direction graphically.
Wind Speed is represented by a short feather, long feather, or pennant. A short feather represents 5 mph, a long feather represents 10 mph, and a pennant represents 50 mph. The sum of all these markings on the wind barb represent the total wind speed. Take a look at these examples:
Wind Direction is represented by the direction that the wind barb is pointing. The wind flows along the shaft, from the feathers to the dot. For example:
Have students complete the wind barb worksheet.WIND BARB ASSESSMENT
Isobars can be used to identify "Highs" and "Lows". The pressure in a high is greater than the surrounding air. The pressure in a low is lower than the surrounding air.
Changes in barometric pressure are more significant than the current pressure readings. Rising pressure means fair weather is on the way. Falling pressures predict bad weather coming.
High pressure regions are usually associated with dry weather because as the air sinks it warms and the moisture evaporates. Low pressure regions usually bring precipitation because when the air rises it cools and the water vapor condenses.
An easy way to remember this is H=High=Happy, L=Low=Lousy
Atmospheric pressure is represented on a map as circled areas (Isobars) that each contain an area of similar pressure. Sea level pressure is measured in millibars (mb). The labels are "short hand" that show just the last two digits: 998mb becomes "98", 999 mb is "99" 1000mb is "00" and 1001 mb is "01" and so on.
Hand out the Atmospheric Pressure/Dewpoint Handout.
Use the Atmospheric Pressure/Dewpoint key as your reference.
Explain to your students that a change in atmospheric pressure indicates a change in weather. Ship's captains rely on these weather reports as they travel on their journey and as such, record these reports in their Captain's Log.
Students will locate significant areas of changing pressure, either to a lower pressure or higher. The handout contains an area of each (marked blue for lowering and red for rising on the key).
Begin a class discussion on what impacts on travel the lowering air pressure could have on the progress the ship makes.ATMOSPHERIC PRESSURE ASSESSMENT
Dewpoint temperature is the temperature to which the air would need to cool to reach saturation (at a constant air pressure and water vapor content). When the air temperature has cooled to the dewpoint temperature, the relative humidity is 100%. Any further cooling will result in condensation.
When air temperature and dewpoint temperature are very close to each other, relative humidity is high. At ground level, air is almost completely saturated and cloud or fog development is possible. If air temperature and dewpoint temperature are far apart, relative humidity is low. Cloud and fog formation is unlikely to occur.
To form any type of fog, there must be calm or light winds and the temperature and dewpoint must approach each other. This can occur by either increasing the amount of moisture in the air or decreasing the temperature in order to achieve a saturated state.
If you are in a situation that's conducive to fog development (meaning that you have clear skies), you can get a lot of radiative heating. Radiative heat causes the surface water to evaporate. Then, as the air moves over the water surface, the amount of moisture in the air increases and thus preconditions the atmosphere for a potential fog event.
A difference of 0 to 3º between air temperature and dewpoint, along with light or calm winds is an indication of fog formation.
By looking at the records for dewpoint, air temperature, and wind speed, your students will be able to make an educated guess as to whether or not the possibility of fog formation is possible.
Hand out the Atmospheric Pressure/Dewpoint Handout.
Use the Atmospheric Pressure/Dewpoint key as your reference. There are several areas where the dewpoint and air temperature are small, but the wind speed is high. Watch that students don't pick these areas as conditions for fog formation. High winds prevent fog formation.
The students will locate conditions that are conducive to fog formation. The handout contains 3 possible areas (marked gray on the key).
Begin a class discussion on what impacts on travel fog could have on the progress the ship makes.DEWPOINT ASSESSMENT
Students will successfully master this lesson upon completion of the latitude/longitude worksheet and weather handouts. Further assessment can be made by the teacher from in-class discussions.