高中英语 Unit2Sailing the oceans-Reading课件 新人教选修9

nautical chart
Nautical charts are maps of the depth of the sea and the currents of the oceans. They provide modern sailors with routes through the seas, rather like roads through the countryside. The information began to be collected in the nineteenth century and has continued to be updated ever since. These charts were not available to Captain Bligh or Zheng He.
3. Can you identify these early navigational instruments seamen used and explain how they are used?
1) compass ( in ancient China) 2) astrolabe 3) sextant 4) sea / nautical / marine chart
Speed and time are important in finding out the longitude of a ship because the earth moves fifteen degrees westwards every hour. If you know your direction, speed and time, you can work out the approximate longitude or change in your position in relation to the stars.
A. To set the course of the ship B. To measure the position of the ship C. To measure the speed of the ship
D. To tell the time
2) Why are speed and time important in working out the longitude of a ship?
The handle of the spoon points to the south, while the other side pபைடு நூலகம்ints to the north. When the Sinan is in the still, the handle of the spoon points to the south because of influence of the terrestrial magnetism (地磁).
help them navigate? 3. What natural objects were used to
assist the navigation? 4. Is it easier to measure longitude or
latitude? 5. Do the astrolabe, the quadrant and
4. Which ones do you think are still used today?
Sea charts are still used today.
Read and answer these questions.
1. Where do these materials come from? 2. What did the early navigator use to
Use a compass.
the sextant mean the same thing?
Comprehending
1. Read the passage and answer the following questions.
1) What is the use of a bearing circle,
astrolabe, quadrant or sextant? ( B) What is the use of a compass? ( A)
Discuss
1. How do you think seamen found their way before modern accurate methods of navigation were invented? Kept close to the shore, used nature such as the sun, wind, birds, tide, etc, to help them, and used some of the instruments including a compass, astrolabe, etc.
Reading
The four basic instruments for navigation: Sinan, Inch Astrolabe, Sextant and nautical map.
Sinan, the ancient Chinese compass.
It was invented by Zhang Heng in the Han dynasty. It is made up of a bronze foundation (青铜地盘) and magnetic spoon(磁勺) which is made of natural magnet, positioned right in the central of the foundation.
2. Suppose you were a sea captain aiming to sail round Africa. Discuss in groups:
1) What skills would you seek in your sailors?
2) What problems would you anticipate for this journey?
Wait till the storm is over, and then find your new position and return to your original course.
What would you do Plan of action
if :
You knew your
Use knots to find
3. Read the chart below and fill in your plans of action to deal with them.
What would you do Plan of action if :
You were far from land and a storm arose.
off-course.
and the astrolabe ,
quadrant or sextant
to find out your
position , return to
your former course.
What would you do Plan of action
if :
You were offshore but you needed more food and water.
It has 17 stars listed as well as a map of the sky overhead (for 37 degrees) and the ecliptic (黄道). The time of day or night is on the outside astrolabe edge with noon at the top of the Astrolabe and midnight at the bottom. It comes with a carrying chain, a pouch, and a book on its use. The reverse side has a sight for measuring the elevations of the heavenly bodies.
Follow nesting birds to shore ; look for special cloud formations
or fog over
streams to find
land.
What would you do Plan of action
if :
You wanted to keep a straight course.
The navigator can then see two images, the horizon and the sun side by side. He can then measure the angle between them on a scale at the bottom of the instrument. The scale goes from 0 to 120 degrees. An earlier instrument, called a quadrant, measured in angle in the same way but it could only measure angles from 0 to 90 degrees.
2. Which do you think was easier to work out: latitude or longitude? Latitude, because it was used to measure how far you had traveled from land on a straight line. It was discovered a long time before longitude.
latitude but didn’t your speed and
know your longitude. work out your
approximate
longitude.
What would you Plan of action
do if :
You were blown Use the compass
sextant
The sextant is a navigational instrument for measuring the angle between the horizon and some object in the sky. First a sailor looks at the horizon through an eyepiece. At the same time he can see light from the sun or a star reflected off a small mirror on top of the instrument, onto a second mirror and into the eyepiece.
3) Why is the position of the sun and various stars useful for working out latitude? The position of the sun and stars are useful for working out latitude because they are fixed points in the sky and their movements in relation to the earth are already known. So they can be used to measure a ship's position.