Unit2 Sailing the Oceans Warming up 课件（28张）

课件28张PPT。Sailing The OceansCompassAstrolabe(星盘)Sextant(六分仪)Sea/nautical chartBearing Circle(方位圆）Quadrant（象限仪）Early navigational instrumentsAlongitudelatitude to find/locate/plot their position Key sentence So how did they navigate so well with those ancient instrumentsReading for organizationSo● Knotted RopeCompass The Bearing CircleThe AstrolabeThe Quadrant●The Sextant● ● ● ● 百科全书Reading for information T or F The compass always indicates the North Pole. The seamen could find the direction that the ship needed to go with its help. Using bearing circle, the seamen could tell if he was sailing on his correct rather than a random course. The Bearing Circle proved to be the most accurate and reliable of these early instruments. Astrolabe was a more precise and simplified version of Quadrant. The astrolabe, quadrant and sextant are all connected.Reading for informationThe compass always indicates the North Pole. The seamen could find the direction that the ship needed to go with its help.Ta magnetic pointerReading for information2. Using bearing circle, the seamen could tell if he was sailing on his correct rather than a random course.Trather than Reading for information 3. The Bearing Circle proved to be the most accurate and reliable of these early instruments.The Sextantsomething or somebody that can be depended onFReading for information Astrolabe was a more precise and simplified version of Quadrant.Use a quarter circle rather than the full circle of the astrolabe accurate/correctFQuadrantAstrolabeReading for information The astrolabe, quadrant and sextant are all connected. TThey are development of one another. What are the usage, advantage and disadvantage of astrolabe, quadrant and sextant?Reading for informationReading for understandingtell the position-- measure how high stars above the horizon measure the angle between two fixed objectsmore precise and simplified easier to handle ; more portable reduce the tendency to make mistakes; most accurate and reliableawkward to use as one of the points of reference was the moving ship itself still used the moving ship as one of the fixed points of reference convenient B. inconvenient C. easy D. comfortableHappy MagazinesParaphrase “at the mercy of” in “The voyages of travellers before the 17th century show that they were not at the mercy of the sea with the help of some early navigational instruments.”Reading for understanding Rewrite sth in your own wordsunder the control of the sea.Why are speed and time important in working out the longitude of a ship? Suppose the latitude is fixed. If you can know the speed and time, you can know _____to help you work out the longitude.Reading for understandingchange in your positionA seaman would measure the sun’s shadow and compare it with the height of the sun at midday. Then he could find his latitude. How did he manage to do that?Reading for understandingH90。||+-当地纬度直射点纬度=- The passage is developed by _____.Readin ... ...