unit 2 reading 课件

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1、Unit2Reading课件Discuss1.Howdoyouthinkseamenfoundtheirwaybeforemodernaccuratemethodsofnavigationwereinvented?Keptclosetotheshore,usednaturesuchasthesun,wind,birds,tide,etc,tohelpthem,andusedsomeoftheinstrumentsincludingacompass,astrolabe,etc.2.Whichdoyouthinkwaseasiert

2、oworkout:latitudeorlongitude?Latitude,becauseitwasusedtomeasurehowfaryouhadtraveledfromlandonastraightline.Itwasdiscoveredalongtimebeforelongitude.3.Canyouidentifytheseearlynavigationalinstrumentsseamenusedandexplainhowtheyareused?1)compass(inancientChina)2)astrolabe

3、3)sextant4)sea/nautical/marinechart4.Whichonesdoyouthinkarestillusedtoday?Seachartsarestillusedtoday.Comprehending1.Readthepassageandanswerthefollowingquestions.Whatistheuseofabearingcircle,astrolabe,quadrantorsextant?()Whatistheuseofacompass?()A.Tosetthecourseofthes

4、hipB.TomeasurethepositionoftheshipC.TomeasurethespeedoftheshipD.TotellthetimeAB2)Whyarespeedandtimeimportantinworkingoutthelongitudeofaship?Speedandtimeareimportantinfindingoutthelongitudeofashipbecausetheearthmovesfifteendegreeswestwardseveryhour.Ifyouknowyourdirect

5、ion,speedandtime,youcanworkouttheapproximatelongitudeorchangeinyourpositioninrelationtothestars.3)Whyisthepositionofthesunandvariousstarsusefulforworkingoutlatitude?Thepositionofthesunandstarsareusefulforworkingoutlatitudebecausetheyarefixedpointsintheskyandtheirmove

6、mentsinrelationtotheeartharealreadyknown.Sotheycanbeusedtomeasureaship'sposition.2.SupposeyouwereaseacaptainaimingtosailroundAfrica.Discussingroups:1)Whatskillswouldyouseekinyoursailors?2)Whatproblemswouldyouanticipateforthisjourney?3.Readthepassageagainandusetheinfo

7、rmationtoanalysethenavigationalskills.Usingnature1.Tofindtheship’spositionatseaasailorusedtheNorthStarandthesun.2.Asailorknewthatlandwasnearbyifhesaw________________________________________________________.3.Sailorsused________________________________toincreasetheirs

8、peed.freshseaweed,nestingbirdsreturninghomeintheeveningorfogseacurrentsortidesandwinds4.Thereweretwomethodstofindlongitude:1)______