课文导读课件.ppt

Sailingtheocenas,Readaboutwhatnavigationwaslikebeforemoderninstrumentswereused.,Sailingtheoceans,Page1,Fast-readingHowdidseamenexploretheoceansbeforelatitudeandlongitudemadeitpossibletoplotashipsposition?,Usingnature,KeepingalongsidethecoastlineUsingcelestialbodiesUsingwildlifeUsingtheweatherUsingthesea,Usingcelestialbodies,toplotthepositions,toworkoutthelatitude,aspecialcloudformationindicatesthereislandcloseby,Usingwildlife,Ifseaweedwasfreshandsmelledstrongly,theshipwasclosetoland.,Seabirdscouldbeusedtoshowthewaytolandwhenitwasnowheretobeseen.,Usingtheweather,fog,Tohelpidentifythepositionofastreamorriverwhen,Todirecttheirsailing,Readthetextcarefullyandfillintheblanks.,plot,latitude,Wildlife,way,identify,tidesandcurrents,Page2,Fast-readingWhatskillsdidsailorsusetoexploretheseasanddiscovernewlands?,Usingnavigationalinstruments,1.Findinglongitude,thecompass,2.Findinglatitude,thebearingcircle(方位圆),theastrolabe(星盘),thequadrant(象限仪,四分仪),thesextant(六分仪),Sunheight,horizon,Writedowntheworkingprinciplesofthefollowinginstruments:,Bearingcircle:tocomparetheheightofthesunnowwiththepositionofthesunatmidday.,Detailreading,Astrolabe:tocomparethepositionoftheshipinrelationtosomestarsorthesun,Quadrant:,amorepreciseformoftheastrolabe,tomeasurehowhighstarsareabovethehorizon,andcomparethatmeasurementwithpreviousmeasurements(usingtheshipasoneofthefixedpointstofinditsposition),Sextant:,anupdatedversionofthequadrantandsoitwasmoreaccurate,tomeasuretheanglebetweentwofixedpointsoutsidetheship(usingtwomirrorstofindtheshipsposition).,ComprehendingPage14,1.Readthepassageandanswerthefollowingquestions.,1)Whatistheuseofabearingcircle,astrolabe,quadrantorsextant?()Whatistheuseofacompass?()A.tosetthecourseoftheshipB.tomeasurethepositionoftheshipC.tomeasurethespeedoftheshipD.totellthetime,B,A,comprehending,2)Whyarespeedandtimeimportantinworkingoutthelongitudeofaship?Speedandtimeareimportantinfindingoutthelongitudeofashipbecausetheearthmovesfifteendegreeswestwardseveryhour.Ifyouknowyourdirection,speedandtime,youcanworkouttheapproximatelongitudeorchangeinyourpositioninrelationtothestars.,3)Whyisthepositionofthesunandvariousstarsusefulforworkingoutlatitude?Thepositionofthesunandstarsareusefulforworkingoutlatitudebecausetheyarefixedpointsintheskyandtheirmovementsinrelationtotheeartharealreadyknown.Sotheycanbeusedtomeasureashipsposition.,2.SupposeyouwereaseacaptainaimingtosailroundAfrica.Discussingroups:,1)Whatskillswouldyouseekinyoursailors?Thesailorswouldneedtobeexcellentnavigators,abletocopewithbothhotandcoldweather,experiencedinsailingthroughverybadweatherandabletoco-operateinateam.2)Whatproblemswouldyouanticipateforthisjourney?Iwouldanticipateveryhotweather(aroundtheequator),coldweather(aroundtheCapeofGoodHope),verystormyseas(aroundtheCape),andproblemswithfoodandwater(unlesshelpedbylocalnativesthewatermaybecontaminatedandthefoodscarce),etc.,3.Readthechartbelowandfillinyourplansofactiontodealwiththem.,Waittillthestormisover,andthenfindyournewpositionandreturntoyouroriginalcourse.,Useknotstofindyourspeedandworkoutyourapproximatelongitude.,Usethecompassandtheastrolabe,quadrantorsextanttofindoutyourposition,returntoyourformercourse.,Follownestingbirdstoshore;lookforspecialcloudformationsorfogoverstreamstofindland.,Useacompass.,Measureyourpositionusingthesunorstars;lookforseabirds,cloudformations,fogorseaweedtoshowthatlandisnearby.,Typeofwriti