地文航海習題（英文版）

1.Thegeographicalpositionofaplaceisdefinedbyits____.

A.latitudeandlongitude

B.altitudeandazimuth

C.declinationandright-ascension

D.Greenwichhourangleandsiderealhourangle

Answer:A.LatitudeandlongitudeareusedtodefinethegeographicalpositionofaplaceontheEarth'ssurface.Altitudeandazimutharerelatedtothepositionofanobjectintheskyrelativetoanobserver.Declinationandright-ascensionareusedinastronomy.Greenwichhourangleandsiderealhouranglearealsoastronomicalconcepts.

2.Thedifferencebetweentruenorthandmagneticnorthiscalled____.

A.deviation

B.variation

C.compasserror

D.magneticdip

Answer:B.Variationistheangulardifferencebetweentruenorthandmagneticnorth.Deviationistheerrorcausedbytheship'smagneticfieldonthecompass.Compasserroristhecombinationofvariationanddeviation.MagneticdipistheanglebetweenthehorizontalandtheEarth'smagneticfield.

3.Thenauticalmileisbasedon____.

A.oneminuteofarcofagreatcircleontheEarth'ssurface

B.onedegreeofarcofagreatcircleontheEarth'ssurface

C.thelengthofameridianontheEarth'ssurface

D.thecircumferenceoftheEarthattheequator

Answer:A.AnauticalmileisdefinedasoneminuteofarcofagreatcircleontheEarth'ssurface.Onedegreeofarcofagreatcircleisequalto60nauticalmiles.

4.Ifthecoursetosteeris090°T,thevariationis10°E,andthedeviationis5°W,whatisthecompasscourse?

A.085°C

B.095°C

C.090°C

D.080°C

Answer:A.TrueCourse(TC)=090°T,Variation(Var)=10°E,Deviation(Dev)=5°W.CompassCourse(CC)=TC-Var+Dev.So,CC=090-10+5=085°C.

5.TheGreenwichMeridianisalsoknownasthe____.

A.PrimeMeridian

B.Equator

C.InternationalDateLine

D.TropicofCancer

Answer:A.TheGreenwichMeridianisdefinedasthePrimeMeridian(0°longitude).TheEquatorisat0°latitude.TheInternationalDateLineisapproximatelyat180°longitude.TheTropicofCancerisat23.5°Nlatitude.

6.Ashipissteamingataspeedof15knots.Howfarwillittravelin3hours?

A.30nauticalmiles

B.45nauticalmiles

C.60nauticalmiles

D.75nauticalmiles

Answer:B.Distance=Speed×Time.Givenspeed=15knotsandtime=3hours.So,distance=15×3=45nauticalmiles.

7.Whenconvertingfrommagnetictotrue,ifthevariationiseast,you____.

A.addthevariationtothemagneticcourse

B.subtractthevariationfromthemagneticcourse

C.addthedeviationtothemagneticcourse

D.subtractthedeviationfromthemagneticcourse

Answer:A.Whenconvertingfrommagnetictotrueandthevariationiseast,youaddthevariationtothemagneticcourse(TC=MC+Var(east)).

8.Thegreat-circledistancebetweentwopointsisthe____.

A.shortestdistancebetweenthetwopointsonthesurfaceofasphere

B.longestdistancebetweenthetwopointsonthesurfaceofasphere

C.distancealongarhumblinebetweenthetwopoints

D.distancemeasuredalongaparalleloflatitudebetweenthetwopoints

Answer:A.Thegreat-circledistanceistheshortestdistancebetweentwopointsonthesurfaceofasphere.Arhumblineisalineofconstantcompassbearingandisnottheshortestdistancebetweentwonon-collinearpointsonasphere.

9.Aship'spositionisdeterminedbytakingbearingsoftwoknownlandmarks.Thismethodiscalled____.

A.cross-bearing

B.deadreckoning

C.celestialnavigation

D.pilotage

Answer:A.Cross-bearingisthemethodofdeterminingaship'spositionbytakingbearingsoftwoormoreknownlandmarks.Deadreckoningisestimatingtheship'spositionbasedoncourseandspeed.Celestialnavigationusescelestialbodies.Pilotageisnavigationinrestrictedwatersusingvisualreferences.

10.Thelatitudeofaplaceismeasured____.

A.northorsouthoftheEquator

B.eastorwestofthePrimeMeridian

C.fromthecenteroftheEarth

D.relativetothemagneticnorth

Answer:A.LatitudeismeasurednorthorsouthoftheEquator,rangingfrom0°attheEquatorto90°NattheNorthPoleand90°SattheSouthPole.

11.Ifashipsailsarhumblinecourse,the____.

A.compasscourseremainsconstant

B.great-circlecourseremainsconstant

C.latituderemainsconstant

D.longituderemainsconstant

Answer:A.Arhumblineisalineofconstantcompassbearing,sothecompasscourseremainsconstantwhensailingonarhumbline.

12.Theisogoniclinesonachartconnectpointsof____.

A.equalmagneticvariation

B.equalmagneticdip

C.equallatitude

D.equallongitude

Answer:A.Isogoniclinesconnectpointsofequalmagneticvariationonachart.

13.Ashipisonacourseof180°T.Thesetofthecurrentis090°andthedriftis2knots.Iftheship'sspeedis10knots,whatisthespeedmadegoodovertheground?

A.10.2knots

B.12knots

C.8knots

D.9.8knots

Answer:A.UsingthePythagoreantheoremfortheresultantoftheship'sspeedthroughthewaterandthecurrent.Ship'sspeed(v1)=10knots,currentspeed(v2)=2knots.Speedmadegood\(v=\sqrt{10^{2}+2^{2}}=\sqrt{100+4}=\sqrt{104}\approx10.2\)knots.

14.Themagneticmeridianisthedirection____.

A.oftheEarth'smagneticfieldataparticularplace

B.oftruenorth

C.ofthePrimeMeridian

D.oftheEquator

Answer:A.ThemagneticmeridianisthedirectionoftheEarth'smagneticfieldataparticularplace.

15.WhenplottingapositiononachartusingaGPSfix,youshould____.

A.checktheaccuracyofthefixagainstotheravailableinformation

B.relysolelyontheGPSfix

C.ignoretheGPSfixifitdoesn'tmatchyourdead-reckoningposition

D.usetheGPSfixonlyforlong-distancenavigation

Answer:A.ItisgoodpracticetochecktheaccuracyofaGPSfixagainstotheravailableinformationsuchasvisualbearingsorradarfixes.

16.Thespeedofashipisusuallymeasuredin____.

A.knots

B.milesperhour

C.kilometersperhour

D.feetpersecond

Answer:A.Innauticalterms,thespeedofashipisusuallymeasuredinknots(1knot=1nauticalmileperhour).

17.ThedifferencebetweenthetimeatthePrimeMeridianandthetimeataparticularplaceisrelatedtothe____.

A.longitudeoftheplace

B.latitudeoftheplace

C.magneticvariationoftheplace

D.altitudeoftheplace

Answer:A.ThetimedifferencebetweenthePrimeMeridian(Greenwich)andaparticularplaceisrelatedtothelongitudeoftheplace.Each15°oflongitudecorrespondstoatimedifferenceof1hour.

18.Aship'scourseis270°T.Thewindiscomingfromthenorth.Theshipissailing____.

A.down-wind

B.up-wind

C.onabeamreach

D.close-hauled

Answer:A.Sincethewindiscomingfromthenorthandtheship'scourseis270°T(west),theshipissailingdown-wind(inthedirectionofthewind).

19.Tofindthemagneticcoursefromthetruecourse,ifthevariationiswest,you____.

A.subtractthevariationfromthetruecourse

B.addthevariationtothetruecourse

C.addthedeviationtothetruecourse

D.subtractthedeviationfromthetruecourse

Answer:A.Whenconvertingfromtruetomagneticandthevariationiswest,yousubtractthevariationfromthetruecourse(MC=TC-Var(west)).

20.Therhumblinebetweentwopointscutsallmeridiansat____.

A.aconstantangle

B.arightangle

C.ananglethatvaries

D.anangleof45degrees

Answer:A.Arhumblinecutsallmeridiansataconstantangle,whichmeansithasaconstantcompassbearing.

21.Ashipisat30°N,120°E.Ifitsailsduewestalongtheparalleloflatitudefor60nauticalmiles,itsnewlongitudewillbe____.

A.121°E

B.119°E

C.120°30'E

D.119°30'E

Answer:B.Onenauticalmilealongaparalleloflatitudecorrespondstooneminuteoflongitudeattheequator.At30°N,thedistanceperminuteoflongitudeis\(\cos(30^{\circ})\)timesthedistanceattheequator.Butforsimplicity,ifweassumeasphericalEarthandapproximate,60nauticalmilesalongaparalleloflatitudeisapproximately1°oflongitudechange.Sailingwest,thelongitudedecreases,sothenewlongitudeis119°E.

22.Themagneticdipiszeroatthe____.

A.magneticequator

B.geographicequator

C.PrimeMeridian

D.InternationalDateLine

Answer:A.Themagneticdipiszeroatthemagneticequator.Atthemagneticpoles,themagneticdipis90°.

23.Aship'scompasshasadeviationof3°E.Ifthemagneticcourseis045°,thecompasscourseis____.

A.042°C

B.048°C

C.045°C

D.040°C

Answer:B.CompassCourse(CC)=MagneticCourse(MC)+Deviation(Dev).GivenMC=045°andDev=3°E.So,CC=045+3=048°C.

24.Thegreat-circletrackbetweentwopointsiscurvedona____.

A.Mercatorprojectionchart

B.Gnomonicprojectionchart

C.Polyconicprojectionchart

D.Lambertconformalconicprojectionchart

Answer:A.OnaMercatorprojectionchart,thegreat-circletrackiscurved,whilearhumblineisastraightline.Onagnomonicprojectionchart,great-circletracksarestraightlines.

25.Ashipissteamingat18knots.Howlongwillittaketotravel90nauticalmiles?

A.3hours

B.4hours

C.5hours

D.6hours

Answer:C.Time=Distance/Speed.Givendistance=90nauticalmilesandspeed=18knots.So,time=90/18=5hours.

26.Whentakingabearingofalandmark,thebearingshouldbemeasured____.

A.fromthecenteroftheship

B.fromthebowoftheship

C.fromthesternoftheship

D.fromthebridgewing

Answer:A.Bearingsoflandmarksareusuallymeasuredfromthecenteroftheshiptoensureconsistency.

27.Thelatitudeofaplacecanbedeterminedbyobservingthe____.

A.altitudeofacelestialbody

B.azimuthofacelestialbody

C.declinationofacelestialbody

D.right-ascensionofacelestialbody

Answer:A.Byobservingthealtitudeofacelestialbodyandusingappropriatecelestialnavigationmethods,thelatitudeofaplacecanbedetermined.

28.Aship'spositionisobtainedbytakingasingleradarrangefromaknownlandmarkandavisualbearingofanotherlandmark.Thismethodiscalled____.

A.range-bearingfix

B.cross-bearing

C.deadreckoning

D.celestialfix

Answer:A.Arange-bearingfixisobtainedbytakingaradarrangefromonelandmarkandabearingfromanotherlandmark.

29.Themagneticnorthpoleislocated____.

A.nearthegeographicnorthpolebutnotatthesamelocation

B.atthegeographicnorthpole

C.attheequator

D.attheInternationalDateLine

Answer:A.Themagneticnorthpoleisnearthegeographicnorthpolebutnotatthesamelocation.

30.Ifaship'struecourseis135°Tandthevariationis5°W,themagneticcourseis____.

A.130°M

B.140°M

C.135°M

D.132°M

Answer:A.MagneticCourse(MC)=TrueCourse(TC)-Variation(Var).GivenTC=135°TandVar=5°W.So,MC=135-5=130°M.

31.Thedistancebetweentwoconsecutiveparallelsoflatitudeisapproximately____.

A.60nauticalmiles

B.1nauticalmile

C.111kilometers

D.1degree

Answer:A.Thedistancebetweentwoconsecutiveparallelsoflatitude(1°difference)isapproximately60nauticalmiles.

32.Ashipissailingonacourseof090°T.Thecurrenthasasetof180°andadriftof3knots.Theship'sspeedthroughthewateris12knots.Thespeedmadegoodoverthegroundintheeast-westdirectionis____.

A.12knots

B.9knots

C.15knots

D.10knots

Answer:A.Thecurrentisinthenorth-southdirection(180°).Theship'sspeedintheeast-westdirection(090°T)isitsspeedthroughthewater,whichis12knots.Thecurrentdoesnotaffecttheeast-westcomponentoftheship'smotion.

33.Thedifferencebetweenthecompasscourseandthemagneticcourseiscalled____.

A.deviation

B.variation

C.compasserror

D.magneticdip

Answer:A.Deviationisthedifferencebetweenthecompasscourseandthemagneticcourse.

34.Thegreat-circleroutebetweentwopointsonasphereisthearcofa____.

A.greatcirclepassingthroughthetwopoints

B.smallcirclepassingthroughthetwopoints

C.rhumblinepassingthroughthetwopoints

D.paralleloflatitudepassingthroughthetwopoints

Answer:A.Thegreat-circleroutebetweentwopointsonasphereisthearcofagreatcirclepassingthroughthetwopoints.

35.Ashipisat40°S,150°W.Ifitsailsduesouthfor30nauticalmiles,itsnewlatitudewillbe____.

A.40°30'S

B.39°30'S

C.41°S

D.39°S

Answer:A.Onenauticalmilealongameridiancorrespondstooneminuteoflatitude.Sailingsouth,thelatitudeincreases.So,30nauticalmilessouthfrom40°Sgivesanewlatitudeof40°30'S.

36.Whenusingamagneticcompassonaship,thedeviationiscausedby____.

A.theship'smagneticfield

B.theEarth'smagneticfield

C.theSun'smagneticfield

D.theMoon'smagneticfield

Answer:A.Deviationiscausedbytheship'smagneticfieldaffectingthemagneticcompass.

37.Aship'spositionisestimatedbydeadreckoning.Thismethodtakesintoaccount____.

A.theship'scourseandspeed

B.thepositionsofcelestialbodies

C.thebearingsoflandmarks

D.theradarrangesoflandmarks

Answer:A.Deadreckoningestimatesaship'spositionbasedontheship'scourseandspeedfromaknownstartingpoint.

38.Theequatorisa____.

A.greatcircle

B.smallcircle

C.rhumbline

D.meridian

Answer:A.Theequatorisagreatcircle(acirclewhosecentercoincideswiththecenteroftheEarth).

39.Ifashipsailsonagreat-circlecoursefrompointAtopointB,thecompasscourse____.

A.willchangecontinuously

B.willremainconstant

C.willchangeonlyatthemid-point

D.willchangeby90degrees

Answer:A.Whensailingonagreat-circlecourse,thecompasscoursewillchangecontinuouslybecauseagreat-circlecutsmeridiansatdifferentangles.

40.Themagneticvariationataparticularplace____.

A.changesslowlyovertime

B.remainsconstantovertime

C.changesonlywiththeseason

D.changesonlywiththetimeofday

Answer:A.ThemagneticvariationataparticularplacechangesslowlyovertimeduetothemovementoftheEarth'smagneticfield.

41.Ashipisat20°N,150°W.Ifitsailsduenorthalongameridianfor120nauticalmiles,itsnewlatitudewillbe____.

A.22°N

B.18°N

C.20°2'N

D.19°40'N

Answer:A.Onenauticalmilealongameridiancorrespondstooneminuteoflatitude.120nauticalmilesis2°oflatitude.Sailingnorthfrom20°N,thenewlatitudeis22°N.

42.Therhumblinedistancebetweentwopointsisusually____.

A.longerthanthegreat-circledistance

B.shorterthanthegreat-circledistance

C.equaltothegreat-circledistance

D.halfofthegreat-circledistance

Answer:A.Therhumblinedistancebetweentwopointsisusuallylongerthanthegreat-circledistancebecausethegreat-circleistheshortestdistancebetweentwopointsonasphere.

43.Aship'scompasshasadeviationof2°W.Ifthemagneticcourseis225°,thecompasscourseis____.

A.223°C

B.227°C

C.225°C

D.220°C

Answer:A.CompassCourse(CC)=MagneticCourse(MC)-Deviation(Dev).GivenMC=225°andDev=2°W.So,CC=225-2=223°C.

44.ThelatitudeoftheNorthPoleis____.

A.90°N

B.0°

C.90°S

D.180°

Answer:A.ThelatitudeoftheNorthPoleis90°N.

45.Whenconvertingfromtruetomagnetic,ifthevariationiswest,you____.

A.subtractthevariationfromthetruecourse

B.addthevariationtothetruecourse

C.addthedeviationtothetruecourse

D.subtractthedeviationfromthetruecourse