课文导读课件

1、Read about what navigation was like before modern instruments were used.Sailing the oceansPage 1Fast-reading How did seamen explore the oceans before latitude and longitude made it possible to plot a ships position?Using nature l Keeping alongside the coastlinel Using celestial bodiesl Using wildlif

2、el Using the weatherl Using the seaUsing celestial bodiesto plot the positionsto work out the latitudea special cloud formation indicates there is land close byUsing wildlifeIf seaweed was fresh and smelled strongly, the ship was close to land.Sea birds could be used to show the way to land when it

3、was nowhere to be seen.Using the weatherTo help identify the position of a stream or river whenTo direct their sailingRead the text carefully and fill in the blanks.NatureCelestial bodies were used to_ the positions of navigators and to work out their_._was used to tell where the ship was close to l

4、and or to show the _ to land. plotlatitudeWildlifewayThe weather could help _the position of a stream or river and to direct the sailing.Certain_ on the sea were used to carry ships to the destination.identifytides and currentsPage 2Fast-readingWhat skills did sailors use to explore the seas and dis

5、cover new lands?Using navigational instruments 1. Finding longitudethe compass 2. Finding latitudel the bearing circle (方位圆方位圆)l the astrolabe (星盘星盘)l the quadrant (象限仪象限仪,四分仪四分仪)l the sextant (六分仪六分仪)Sun heighthorizon Write down the working principles of the following instruments: Bearing circle: t

6、o compare the height of the sun now with the position of the sun at midday. Detail readingAstrolabe: to compare the position of the ship in relation to some stars or the sun Quadrant: a more precise form of the astrolabe, to measure how high stars are above the horizon, and compare that measurement

7、with previous measurements (using the ship as one of the fixed points to find its position) Sextant:an updated version of the quadrant and so it was more accurate, to measure the angle between two fixed points outside the ship (using two mirrors to find the ships position). 1)What is the use of a be

8、aring circle, astrolabe, quadrant or sextant? ( ) What is the use of a compass? ( ) 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 timeB BA Acomprehending 2)Why are speed and time important in working out the longitude of a

9、ship? 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. 3)Why is the position of

10、 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 ships position. 1)What skills wo

11、uld you seek in your sailors?The sailors would need to be excellent navigators, able to cope with both hot and cold weather, experienced in sailing through very bad weather and able to co-operate in a team. 2)What problems would you anticipate for this journey?I would anticipate very hot weather (ar

12、ound the equator), cold weather (around the Cape of Good Hope), very stormy seas (around the Cape), and problems with food and water (unless helped by local natives the water may be contaminated and the food scarce), etc.3. Read the chart below and fill in your plans of action to deal with them.What

13、 would you do if : Plan of actionYou were far from land and a storm arose.Wait till the storm is over, and then find your new position and return to your original course. What would you do if :Plan of actionYou knew your latitude but didnt know your longitude.Use knots to find your speed and work ou

14、t your approximate longitude.What would you do if :Plan of actionYou were blown off-course.Use the compass and the astrolabe , quadrant or sextant to find out your position , return to your former course. What would you do if :Plan of actionYou were offshore but you needed more food and water.Follow

15、 nesting birds to shore ;look for special cloud formations or fog over streams to find land. What would you do if :Plan of actionYou wanted to keep a straight course. Use a compass.What would you do if :Plan of actionYou were lost with no land in sight. Measure your position using the sun or stars; look for sea birds, cloud formations, fog or sea-weed to show that land is nearby.Type of writing and summary of SAILING THE OCEAN.