资源描述:
《Warmingup、Pre-reading、Reading、Comprehending (3).ppt》由会员上传分享,免费在线阅读,更多相关内容在教育资源-天天文库。
1、ReadingThefourbasicinstrumentsfornavigation:Sinan,InchAstrolabe,Sextantandnauticalmap.Sinan,theancientChinesecompass.ItwasinventedbyZhangHengintheHandynasty.Itismadeupofabronzefoundation(青铜地盘)andmagneticspoon(磁勺)whichismadeofnaturalmagnet,positionedrightinthecentr
2、alofthefoundation.Thehandleofthespoonpointstothesouth,whiletheothersidepointstothenorth.WhentheSinanisinthestill,thehandleofthespoonpointstothesouthbecauseofinfluenceoftheterrestrialmagnetism(地磁).Ithas17starslistedaswellasamapoftheskyoverhead(for37degrees)andtheec
3、liptic(黄道).ThetimeofdayornightisontheoutsideedgewithnoonatthetopoftheAstrolabeandmidnightatthebottom.Itcomeswithacarryingchain,apouch,andabookonitsuse.Thereversesidehasasightformeasuringtheelevationsoftheheavenlybodies.astrolabesextantThesextantisanavigationalinst
4、rumentformeasuringtheanglebetweenthehorizonandsomeobjectinthesky.Firstasailorlooksatthehorizonthroughaneyepiece.Atthesametimehecanseelightfromthesunorastarreflectedoffasmallmirrorontopoftheinstrument,ontoasecondmirrorandintotheeyepiece.Thenavigatorcanthenseetwoima
5、ges,thehorizonandthesunsidebyside.Hecanthenmeasuretheanglebetweenthemonascaleatthebottomoftheinstrument.Thescalegoesfrom0to120degrees.Anearlierinstrument,calledaquadrant,measuredinangleinthesamewaybutitcouldonlymeasureanglesfrom0to90degrees.nauticalchartNauticalch
6、artsaremapsofthedepthoftheseaandthecurrentsoftheoceans.Theyprovidemodernsailorswithroutesthroughtheseas,ratherlikeroadsthroughthecountryside.Theinformationbegantobecollectedinthenineteenthcenturyandhascontinuedtobeupdatedeversince.ThesechartswerenotavailabletoCapt
7、ainBlighorZhengHe.Discuss1.Howdoyouthinkseamenfoundtheirwaybeforemodernaccuratemethodsofnavigationwereinvented?Keptclosetotheshore,usednaturesuchasthesun,wind,birds,tide,etc,tohelpthem,andusedsomeoftheinstrumentsincludingacompass,astrolabe,etc.2.Whichdoyouthinkwas
8、easiertoworkout:latitudeorlongitude?Latitude,becauseitwasusedtomeasurehowfaryouhadtraveledfromlandonastraightline.Itwasdiscoveredalongtimebeforelongitud