Warmingup、Pre-reading、Reading、Comprehending (3)

Reading,Thefourbasicinstrumentsfornavigation:Sinan,InchAstrolabe,Sextantandnauticalmap.,Sinan,theancientChinesecompass.,ItwasinventedbyZhangHengintheHandynasty.Itismadeupofabronzefoundation(青铜地盘)andmagneticspoon(磁勺)whichismadeofnaturalmagnet,positionedrightinthecentralofthefoundation.,Thehandleofthespoonpointstothesouth,whiletheothersidepointstothenorth.WhentheSinanisinthestill,thehandleofthespoonpointstothesouthbecauseofinfluenceoftheterrestrialmagnetism(地磁).,Ithas17starslistedaswellasamapoftheskyoverhead(for37degrees)andtheecliptic(黄道).ThetimeofdayornightisontheoutsideedgewithnoonatthetopoftheAstrolabeandmidnightatthebottom.Itcomeswithacarryingchain,apouch,andabookonitsuse.Thereversesidehasasightformeasuringtheelevationsoftheheavenlybodies.,astrolabe,sextant,Thesextantisanavigationalinstrumentformeasuringtheanglebetweenthehorizonandsomeobjectinthesky.Firstasailorlooksatthehorizonthroughaneyepiece.Atthesametimehecanseelightfromthesunorastarreflectedoffasmallmirrorontopoftheinstrument,ontoasecondmirrorandintotheeyepiece.,Thenavigatorcanthenseetwoimages,thehorizonandthesunsidebyside.Hecanthenmeasuretheanglebetweenthemonascaleatthebottomoftheinstrument.Thescalegoesfrom0to120degrees.Anearlierinstrument,calledaquadrant,measuredinangleinthesamewaybutitcouldonlymeasureanglesfrom0to90degrees.,nauticalchart,Nauticalchartsaremapsofthedepthoftheseaandthecurrentsoftheoceans.Theyprovidemodernsailorswithroutesthroughtheseas,ratherlikeroadsthroughthecountryside.Theinformationbegantobecollectedinthenineteenthcenturyandhascontinuedtobeupdatedeversince.ThesechartswerenotavailabletoCaptainBlighorZhengHe.,1.Howdoyouthinkseamenfoundtheirwaybeforemodernaccuratemethodsofnavigationwereinvented?,Keptclosetotheshore,usednaturesuchasthesun,wind,birds,tide,etc,tohelpthem,andusedsomeoftheinstrumentsincludingacompass,astrolabe,etc.,2.Whichdoyouthinkwaseasiertoworkout:latitudeorlongitude?,Latitude,becauseitwasusedtomeasurehowfaryouhadtraveledfromlandonastraightline.Itwasdiscoveredalongtimebeforelongitude.,3.Canyouidentifytheseearlynavigationalinstrumentsseamenusedandexplainhowtheyareused?,1)compass(inancientChina)2)astrolabe3)sextant4)sea/nautical/marinechart,4.Whichonesdoyouthinkarestillusedtoday?,Seachartsarestillusedtoday.,1.Wheredothesematerialscomefrom?2.Whatdidtheearlynavigatorusetohelpthemnavigate?3.Whatnaturalobjectswereusedtoassistthenavigation?4.Isiteasiertomeasurelongitudeorlatitude?5.Dotheastrolabe,thequadrantandthesextantmeanthesamething?,Readandanswerthesequestions.,Comprehending,1.Readthepassageandanswerthefollowingquestions.Whatistheuseofabearingcircle,astrolabe,quadrantorsextant?()Whatistheuseofacompass?()A.TosetthecourseoftheshipB.TomeasurethepositionoftheshipC.TomeasurethespeedoftheshipD.Totellthetime,A,B,2)Whyarespeedandtimeimportantinworkingoutthelongitudeofaship?Speedandtimeareimportantinfindingoutthelongitudeofashipbecausetheearthmovesfifteendegreeswestwardseveryhour.Ifyouknowyourdirection,speedandtime,youcanworkouttheapproximatelongitudeorchangeinyourpositioninrelationtothestars.,3)Whyisthepositionofthesunandvariousstarsusefulforworkingoutlatitude?Thepositionofthesunandstarsareusefulforworkingoutlatitudebecausetheyarefixedpointsintheskyandtheirmovementsinrelationtotheeartharealreadyknown.Sotheycanbeusedtomeasureashipsposition.,2.SupposeyouwereaseacaptainaimingtosailroundAfrica.Discussingroups:1)Whatskillswouldyouseekinyoursailors?2)Whatproblemswouldyouanticipateforthisjourney?,Waittillthestormisover,andthenfindyournewpositionandreturntoyouroriginalcourse.,3.Readthechartbelowandfillinyourplansofactiontodealwiththem.,Useknotstofindyourspeedandworkoutyourapproximatelongitude.,Usethecompassandtheastrolabe,quadrantorsextanttofindoutyourposition,returntoyourformercourse.,Follownestingbirdstoshore;lookforspecialcloudformationsorfogoverstreamstofindland.,Useacompass.,Measureyourpositionusingthesunorstars;lookforseabirds,cloudformations,fogorseaweedtoshowthatlandisnearby.,4.Readthepassageagainandusetheinformationtoanalyzethenavigationalskills.,1.TofindtheshipspositionatseaasailorusedtheNorthStarandthesun.2.Asailorknewthatlandwasnearbyifhesaw_.3.Sailorsused_toincreasetheirspeed.,freshseaweed,nestingbirdsreturninghomeintheeveningorfog,seacurrentsortidesandwinds,4.Thereweretwomethodstofindlongitude:1)_2)_,Usinginstruments,measuringtimeandspeed,compassandcomplicatedmathematicaltables,5Writedowntheworkingprinciplesofthefollowinginstruments:Bearingcircle:Astrolabe:,tocomparetheheightofthesunnowwiththepositionofthesunatmidday.,tocomparethepositionoftheshipinrelationtosomestarsorthesun,Quadrant:,amorepreciseformoftheastrolabe,tomeasurehowhighstarsareabovethehorizon,andcomparethatmeasurementwithpreviousmeasurements(usingtheshipasoneofthefixedpointstofinditsposition),Sextant:,anupdatedversionofthequadrantandsoitwasmoreaccurate,tomeasuretheanglebetweentwofixedpointsoutsidetheship(usingtwomirrorstofindtheshipsposition).,5.Imagineyouareonaboatwithtwenty-nineotherpeople.Youhaveasmallboxforyourpersonalthingsbutitcanonlyholetenitems.WhatwouldyouneedforaweeksjourneyacrosstheNorthSeatoEngland?,soap,blanket,cards,chess,shirt,trousers,knife,scissors,sea-sicktablets,coldmedicine,novels,essaycollections,waterproofboots,Readthepassage(Reading)anddecidewhetherthefollowingstatementsaretrue(T)orfalse(F).1.Anearlymethodofcalculatinglongitudewastouseaknottedropetiedtoalog.2.Theastrolabewasthefirstinstrumenttomeasurethesunsposition.3.Thequadrantwasmorepreciseandsimplifiedthantheastrolabe,butstillhaditsshortcoming.,T,F,T,4.Uptillnow,themostaccurateandreliablenavigationalinstrumentisthesextant.5.Theastrolabe,quadrantandsextantaredifferentkindsofnavigati