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人教2003课标版《Warming up、Pre-reading、Reading、Comprehending》公开课PPT课件优质课下载
Zheng He
Christopher Columbus
Ferdinand Magellan
Do you know them?
we call them sailors or navigators
How do you think seaman found their way before modern accurate methods of navigation were invented ?
How did they navigate so well ?
early navigational instruments
compass ['k?mp?s]
astrolabe?[??str?le?b]
星盘
The astrolabe measures the height and position of the sun. From this a captain can tell where the boat is in the ocean.
Sextant (六分仪) is used to measure the angle between the horizon and some object in the sky.
Nautical charts (航海图) are maps of the depth of the sea and the currents of the oceans.
latitude
longitude
Reading
Fast reading
What did people use to help sailing?
nature
instruments
How does nature help sailing the oceans?
What can instruments help to do?
Using celestial bodies
to plot the positions