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Unit2Wordsminimumpoleoverheadoffshoreoutwardsecuremagneticadj.最小的;最低的n.地极;柱;杆adj.在头上的adv.在头顶上;在空中adj.离岸的;海面上的adj.外面的;向外的adv.向外;在外adj.安全的;可靠的adj.磁的;有磁性的awkwardreferenceprecisesimplifyportableshortcomingupdatedtendencyreliableadj.难使用的;笨拙的n.参考adj.精确的;准确的vt.单一化;简单化adj.轻便的;手提的n.缺点;短处vt.更新n.趋向;倾向adj.可靠的;可信赖的1Whatisanavigator?2Whatisthedifferencebetweenanavigatorandanexplorer?Inpairsdiscussthesequestions:Anavigatorexploresnewroutesacrossthesea.Anavigatorexploresthesea;anexplorerdiscoversnewplacesonland.3Lookatthesefamouspeople.Aretheynavigatorsorexplorers?Whatdoyouknowaboutthem?ZhengHe,intheyearbetween1405and1433,sevenlargetreasurefleetssailedwestwardsonvoyagesoftradeandexploration.UnderthecommandofZhengHe,thefleetssetsailfromtheSouthChinaSeaacrosstheIndianOceantotheRedSea,andthentraveledfurthersouth,discoveringtheeasterncoastofAfrica.HerenewedrelationswiththeKingdomsoftheEastAfrican.WhenMarcoPolowasstillveryyoung,hedecidedtotraveltogetherwithhisfather.IttookthemmorethanthreeyearstotraveltoChina.Afternearlyseventeenyears’travelintheEast,Marcoandhisfatherwantedtoreturnhome.MarcoPoloMarcoPolowasborninVenicein1254.HewasthemostfamousforeignertovisitAsiaduringtheMiddleAges.JamesCook(1728-1779)wasthegreatestBritainnavigator.CookenlistedintheRoyalNavyin1755.In1768hewaspromotedandsenttothePacificwherehesurveyedTahiti,NewZealand,andAustralia.Onhisfamous2ndexpedition(1772-75)heexploredAntarctica.In1776inhisthirdandfinalvoyage,heexploredtheWestcoastofNorthAmericaanddiscoveredtheHawaiianIslands.Navigatorissomeonewhofindsthepositionandplotsthecourseofaship,anaircraft,acar,etc,usingmapsandinstruments.NavigatorseanauticalinstrumentsfindnewislandsorcontinentsExplorerissomeonewhotravelsintoorthroughaplaceinordertolearnaboutit.Veryoftennavigatorsarealsoexplorers.Explorerlanduseofcompassandlandmarksfindnewplaceswithinanalreadyidentifiedislandorcontinent1Howdoyouthinkseamenfoundtheirwaybeforemodernaccuratemethodsofnavigationwereinvented?Lookatthepicturesonpage11.Thenanswerthequestions.Keptclosetotheshore,usednaturesuchasthesun,wind,birds,tide,etc,tohelpthem,andusedsomeoftheinstrumentsincludingacompass,astrolabe,etc.2Whichdoyouthinkwaseasiertoworkout:latitudeorlongitude?Latitude,becauseitwasusedtomeasurehowfaryouhadtravelledfromlandonastraightline.Itwasdiscoveredalongtimebeforelongitude.3Canyouidentifytheseearlynavigationalinstrumentsseamenusedandexplainhowtheyareused?1_________________________2_________3_________4________________________compass(inancientChina)astrolabesextantsea/nautical/marinechart4Whichonesdoyouthinkarestillusedtoday?Seachartsarestillusedtoday.SAILINGTHEOCEANSNowreadaboutwhatnavigationwaslikebeforemoderninstrumentswereused.1Whatistheuseofabearingcircle,astrolabe,quadrantorsextant?()Whatistheuseofacompass?()AtosetthecourseoftheshipBtomeasurethepositionoftheshipCtomeasurethespeedoftheshipDtotellthetimeBA1Readthepassageandanswerthefollowingquestions.Speedandtimeareimportantinfindingoutthelongitudeofashipbecausetheearthmovesfifteendegreeswestwardseveryhour.Ifyouknowyourdirection,speedandtime,youcanworkouttheapproximatelongitudeorchangeinyourpositioninrelationtothestars.2Whyarespeedandtimeimportantinworkingoutthelongitudeofaship?Thepositionofthesunandstarsareusefulforworkingoutlatitudebecausetheyarefixedpointsintheskyandtheirmovementsinrelationtotheeartharealreadyknown.Sotheycanbeusedtomeasureaship'sposition.3Whyisthepositionofthesunandvariousstarsusefulforworkingoutlatitude?Thesailorswouldneedtobeexcellentnavigators,abletocopewithbothhotandcoldweather,experiencedinsailingthroughverybadweatherandabletoco-operateinateam.2SupposeyouwereaseacaptainaimingtosailroundAfrica.Discussingroups:1Whatskillswouldyouseekinyoursailors?Iwouldanticipateveryhotweather(aroundtheequator),coldweather(aroundtheCapeofGoodHope),verystormyseas(aroundtheCape),andproblemswithfoodandwater(unlesshelpedbylocalnativesthewatermaybecontaminatedandthefoodscarce),etc.2Whatproblemswouldyouanticipateforthisjourney?SAILINGTHEOCEANSUsingnaturetokeepalongsidecoastlinePart1UsingnavigationalinstrumentstohelpPart2UsingcelestialbodiesUsingthewildlifeFindinglongitudeUsingtheseaFindinglatitudeUsingtheweather3Whatwouldyoudoifyoucameacrossthefollowingproblemsduringyourvoyage?Readthechartbelowandfillinyourplansofactiontodealwiththem.Whatwouldyoudoif:PlanofactionYouwerefarfromlandandastormarose.waittillthestormisover,andthenfindyournewpositionandreturntoyouroriginalcourseYouknewyourlatitudebutdidn'tknowyourlongitude.Youwereblownoff-course.useknotstofindyourspeedandworkoutyourapproximatelongitudeusethecompassandtheastrolabe,quadrantorsextanttofindoutyourposition,returntoyourformercourseYouwereoffshorebutyouneededmorefoodandwater.Youwantedtokeepastraightcourse.follownestingbirdstoshore;lookforspecialcloudformationsorfogoverstreamstofindlanduseacompassYouwerelostwithnolandinsight.measureyourpositionusingthesunorstars;lookforseabirds,cloudformations,fogorseaweedtoshowthatlandisnearby1Tofindtheship’spositionatseaasailorusedtheNorthStarandthesun.4Readthepassageagainandusethe