课文导读课件.ppt

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1、SailingtheocenasReadaboutwhatnavigationwaslikebeforemoderninstrumentswereused.SailingtheoceansPage1Fast-readingHowdidseamenexploretheoceansbeforelatitudeandlongitudemadeitpossibletoplotaship’sposition?UsingnatureKeepingalongsidethecoastlineUsingcelestialbodiesU

2、singwildlifeUsingtheweatherUsingtheseaUsingcelestialbodiestoplotthepositionstoworkoutthelatitudeaspecialcloudformationindicatesthereislandclosebyUsingwildlifeIfseaweedwasfreshandsmelledstrongly,theshipwasclosetoland.Seabirdscouldbeusedtoshowthewaytolandwhenitwa

3、snowheretobeseen.UsingtheweatherfogTohelpidentifythepositionofastreamorriverwhen…TodirecttheirsailingReadthetextcarefullyandfillintheblanks.NatureCelestialbodieswereusedto_____thepositionsofnavigatorsandtoworkouttheir_______._______wasusedtotellwheretheshipwasc

4、losetolandortoshowthe____toland.plotlatitudeWildlifewayTheweathercouldhelp_______thepositionofastreamorriverandtodirectthesailing.Certain________________ontheseawereusedtocarryshipstothedestination.identifytidesandcurrentsPage2Fast-readingWhatskillsdidsailorsus

5、etoexploretheseasanddiscovernewlands?Usingnavigationalinstruments1.Findinglongitudethecompass2.Findinglatitudethebearingcircle(方位圆)theastrolabe(星盘)thequadrant(象限仪,四分仪)thesextant(六分仪)SunheighthorizonWritedowntheworkingprinciplesofthefollowinginstruments:Bearingc

6、ircle:tocomparetheheightofthesunnowwiththepositionofthesunatmidday.DetailreadingAstrolabe:tocomparethepositionoftheshipinrelationtosomestarsorthesunQuadrant:amorepreciseformoftheastrolabe,tomeasurehowhighstarsareabovethehorizon,andcomparethatmeasurementwithprev

7、iousmeasurements(usingtheshipasoneofthefixedpointstofinditsposition)Sextant:anupdatedversionofthequadrantandsoitwasmoreaccurate,tomeasuretheanglebetweentwofixedpointsoutsidetheship(usingtwomirrorstofindtheship'sposition).ComprehendingPage141.Readthepassageandan

8、swerthefollowingquestions.1)Whatistheuseofabearingcircle,astrolabe,quadrantorsextant?()Whatistheuseofacompass?()A.tosetthecourseoftheshipB.tomeasurethepositionoftheshipC.tom