電子與通信技術(shù)專業(yè)英語（第6版）課件 項(xiàng)目16 Global Positioning System (GPS)

劉騁蔡靜主編電子與通信技術(shù)專業(yè)英語（第6版）高職高專電子信息類“十三五”規(guī)劃教材EnglishonElectronicandTelecommunicationTechnology03UnitⅢCommunicationTechnologyLesson16GlobalPositioningSystem(GPS)

UnitⅢNewWordsterrestrial [t?'restri?l] adj. 地球的，地上的latitude ['l?titju:d] n. 緯度longitude ['l?nd?itju:d] n. 經(jīng)度trilateration [,trail?t?'rei??n] n. 【測】三邊測量（術(shù)）redundant [ri'd?nd?nt] adj. 多余的segment ['seɡm(xù)?nt] n. 段；部分orbit ['?:bit] n.&v.軌道，常軌；繞軌道而行NewWordsdelay [di'lei] n.&v.耽擱，延遲ionosphere [ai'?n?sfi?] n. 電離層pseudo ['sju:d?u] adj. 假的，冒充的sequence ['si:kw?ns] n. 序列，繼起的事，順序multiple ['m?ltipl] adj. 多樣的，多重的access ['?kses] n. 通路，進(jìn)入，使用之權(quán)encrypt [in'kript] v. 加密，將……譯成密碼GPSistheGlobalPositioningSystem.GPSusessatellitetechnologytoenableaterrestrialterminaltodetermineitspositionontheEarthinlatitudeandlongitude.Lesson16GlobalPositioningSystem(GPS)ChineseTranslationofTextsGPS是全球衛(wèi)星定位系統(tǒng)。GPS使用衛(wèi)星技術(shù)，能使地面終端確定它在地球上的經(jīng)度和緯度的位置。第16課

全球定位系統(tǒng)（GPS）ChineseTranslationofTextsGPSreceiversdothisbymeasuringthesignalsfromthreeormoresatellitessimultaneouslyanddeterminingtheirpositionusingthetimingofthesesignals（Fig.16-1）.ChineseTranslationofTexts接收器同時(shí)測量來自三個(gè)或三個(gè)以上的衛(wèi)星的信號，并通過這些信號的傳播時(shí)間來確定位置（圖16－1）。ChineseTranslationofTextsGPSoperatesusingtrilateration.Trilaterationistheprocessofdeterminingthepositionofanunknownpointbymeasuringthelengthsofthesidesofanimaginarytrianglebetweentheunknownpointandtwoormoreknownpoints.ChineseTranslationofTexts

GPS的工作使用三邊測量法。三邊測量是指在未知點(diǎn)兩側(cè)有兩個(gè)或兩個(gè)以上的已知點(diǎn)，與未知點(diǎn)呈虛擬的三角形，通過測量未知點(diǎn)到已知點(diǎn)的邊長來確定未知點(diǎn)。ChineseTranslationofTextsIntheGPSsystem,thetwoknownpointsareprovidedbytwoGPSsatellites.Thesesatellitesconstantlytransmitanidentifyingsignal.TheGPSreceivermeasuresthedistancetoeachGPSsatellitebymeasuringthetimeeachsignaltooktotravelbetweentheGPSsatelliteandtheGPSreceiver.ChineseTranslationofTexts在GPS中，兩個(gè)已知點(diǎn)由兩個(gè)全球定位系統(tǒng)衛(wèi)星提供。這些衛(wèi)星不斷傳送一個(gè)確定的信號。GPS接收機(jī)通過測量每一個(gè)信號在GPS衛(wèi)星和GPS接收機(jī)之間傳播的時(shí)間來測量其距離。ChineseTranslationofTextsGPSoperatesusingtrilateration.TheGPSsystemisdividedintothreesegments:TheSpaceSegmentTheControlSegmentTheUserSegmentChineseTranslationofTexts全球衛(wèi)星定位系統(tǒng)分為三個(gè)部分：空間部分控制部分用戶部分ChineseTranslationofTextsGPSusestwenty-oneoperationalsatellites,withanadditionalthreesatellitesinorbitasredundantbackup.GPSusesNAVSTARsatellitesmanufacturedbyRockwellInternational.EachNAVSTARsatelliteisapproximately5meterswide(withsolarpanelsextended)andweighsapproximately900Kg.ChineseTranslationofTexts

GPS使用21顆運(yùn)行衛(wèi)星，軌道中另外還有3顆后備衛(wèi)星。全球定位系統(tǒng)利用由羅克韋爾國際制造的導(dǎo)航衛(wèi)星。每一個(gè)導(dǎo)航衛(wèi)星約5米寬（包括延太陽能發(fā)電板的長度），重量大約900公斤。ChineseTranslationofTextsGPSsatellitesorbittheearthatanaltitudeofapproximately20,200km.EachGPSsatellitehasanorbitalperiodof11hoursand58minutes.ThismeansthateachGPSsatelliteorbitstheEarthtwiceeachday.ChineseTranslationofTexts

GPS衛(wèi)星的軌道離地區(qū)的距離約為20200公里。每個(gè)GPS衛(wèi)星繞軌道一周的時(shí)間為11小時(shí)58分鐘。這意味著每一個(gè)GPS衛(wèi)星每天繞地球兩次。ChineseTranslationofTextsThesetwenty-foursatellitesorbitinsixorbitalplanes,orpaths.ThismeansthatfourGPSsatellitesoperateineachorbitalplane.Eachofthesesixorbitalplanesisspacedsixtydegreesapart.Alloftheseorbitalplanesareinclinedfifty-fivedegreesfromtheEquator.ChineseTranslationofTexts這24顆衛(wèi)星有6個(gè)軌道面，或路徑，這意味著每個(gè)軌道面有4個(gè)GPS衛(wèi)星工作。6個(gè)軌道面的每個(gè)之間呈60度隔開。所有這些軌道面都偏離赤道傾斜55度。ChineseTranslationofTextsInorderforGPStrackingtowork,itisnecessarytohavebothaccesstotheGlobalPositioningSystemandhaveaGPSreceiver(Fig.16-2).TheGPSreceiverisabletoreceivesignalsthataretransmittedbyGPSsatellitesorbitingoverhead.OncethesesatellitetransmissionsarereceivedbytheGPSreceiver,locationandotherinformationsuchasspeedanddirectioncanbecalculated.ChineseTranslationofTexts

GPS為了進(jìn)行跟蹤，既要訪問全球定位系統(tǒng)，還要有一個(gè)全球定位系統(tǒng)接收機(jī)（圖16－2）。全球定位系統(tǒng)接收機(jī)能收到上方繞軌道運(yùn)行的全球定位系統(tǒng)衛(wèi)星傳送的信號。一旦這些衛(wèi)星傳送的信號被全球定位系統(tǒng)接收機(jī)收到，位置及其他信息如速度和方向等就能計(jì)算出來。ChineseTranslationofTextsThereceivercontainsamathematicalmodeltoaccountfortheseinfluences,andthesatellitesalsobroadcastsomerelatedinformationwhichhelpsthereceiverinestimatingthecorrectspeedofpropagation.Certaindelaysources,suchastheionosphere,affectthespeedofradiowavesbasedontheirfrequencies,dualfrequencyreceiverscanactuallymeasuretheeffectsonthesignals.ChineseTranslationofTexts接收機(jī)包含有一個(gè)數(shù)學(xué)模型來計(jì)算這些信息的影響，衛(wèi)星也傳播一些相關(guān)的信息以幫助接收機(jī)正確地估算傳播速度。電離層等一些原因，會影響不同頻率的無線電波的速度,雙頻接收機(jī)能測量它們對信號的影響。ChineseTranslationofTextsInordertomeasurethetimedelaybetweensatelliteandreceiver,thesatellitesendsarepeating1,023bitlongpseudorandomsequence;thereceiverconstructsanidenticalsequenceandshiftsituntilthetwosequencesmatch.ChineseTranslationofTexts為了測量衛(wèi)星和接收機(jī)之間的時(shí)間延遲,衛(wèi)星重復(fù)發(fā)送1,023字節(jié)長的偽隨機(jī)序列；接收機(jī)建立一完全相同的序列和移動(dòng)它直到兩序列匹配。ChineseTranslationofTextsDifferentsatellitesusedifferentsequences,whichletsthemallbroadcastonthesamefrequencieswhilestillallowingreceiverstodistinguishbetweensatellites.ThisisanapplicationofCodeDivisionMultipleAccess,CDMA.ChineseTranslationofTexts不同衛(wèi)星使用不同的序列，這樣，當(dāng)不同的衛(wèi)星發(fā)送相同頻率的信號時(shí)，接收機(jī)能夠區(qū)別它們。這就是碼分復(fù)用（CDMA）的應(yīng)用。ChineseTranslationofTextsTherearetwofrequenciesinuse:1575.42MHz(referredtoasL1),and1227.60MHz(L2).TheL1signalcarriesapubliclyusablecoarse-acquisition(C/A)codeaswellasanencryptedP(Y)code.TheL2signalusuallycarriesonlytheP(Y)code.ChineseTranslationofTexts有兩個(gè)頻率GPS被使用：1575.42MHz（稱之為L1頻率）和1227.60MHz((L2頻率)，L1信號攜帶一個(gè)可公開使用的粗碼(C/A)，和一個(gè)加密碼P(Y)。L2信號通常只攜帶P(Y)碼。ChineseTranslationofTextsNoteslatitudeandlongitude經(jīng)緯度如：Oneusedtorepresentaunitofmeasurement,suchasfeetorminutesinlatitudeandlongitude.

用來代表衡量單位用來代表某一測量單位，如經(jīng)度或緯度上的英尺或分1Notes如：Nothingmaketheearthseemsospaciousastohavefriendatadistance;theymakelatitudeandlongitude.沒有一件事情比得上有朋在遠(yuǎn)方更使這地球顯得如此廣大的了；他們構(gòu)成緯度，也構(gòu)成經(jīng)度。1Notes如：GPSistheGlobalPositioningSystem.GPSusessatellitetechnologytoenableaterrestrialterminaltodetermineitspositionontheEarthinlatitudeandlongitude.GPS是全球衛(wèi)星定位系統(tǒng)。GPS使用衛(wèi)星技術(shù)，能使地面終端確定它在地球上的經(jīng)度和緯度。1Notessimultaneouslyadv.同時(shí)地（聯(lián)立地）如：Thatcannotbesimultaneouslytrue;mutuallyexclusive.互相矛盾的，不能同時(shí)成立的；互斥的2Notes如：Agroupofthreebitsorthreepulses,usuallyinsequenceononewireorsimultaneouslyonthreewires.3個(gè)二進(jìn)制位或3個(gè)脈沖組成的一組，通常按時(shí)間順序出現(xiàn)在一根導(dǎo)線上或同時(shí)出現(xiàn)在3根導(dǎo)線上。2NotesGPSreceiversdothisbymeasuringthesignalsfromthreeormoresatellitessimul-taneouslyanddeterminingtheirpositionusingthetimingofthesesignals.GPS接收器同時(shí)測量來自3個(gè)或3個(gè)以上的衛(wèi)星的信號，并通過這些信號的傳播時(shí)間來確定位置。2NotesNAVSTARsatellites導(dǎo)航衛(wèi)星3NotesRockwellInternational羅克韋爾國際公司例如：GPSusesNAVSTARsatellitesmanufacturedbyRockwellInternational.譯文：全球定位系統(tǒng)采用由羅克韋爾國際公司制造的導(dǎo)航衛(wèi)星。4Notesequatorn.（地球或天球的）赤道；（平分球形物體的面的）圓thecelestialequator：天球赤道theearth’sequator：地球赤道themagneticequator：地磁赤道例如：Alloftheseorbitalplanesareinclinedfifty-fivedegreesfromtheequator.譯文：所有這些軌道面都偏離赤道傾斜55°。5Exercises1.WriteT(True)orF(False)besidethefollowingstatementsaboutthetext.a.GPSusescomputertechnologytoenableaterrestrialterminaltodetermineitspositionontheEarth.b.GPSreceiversdothisbymeasuringthesignalsfromonlyonesatellitessimultaneouslyanddeterminingtheirpositionusingthetimingofthesesignals.c.Trilaterationistheprocessofdeterminingthepositionofanunknownpointbymeasuringthetemperatureofthesidesofanimaginarytrianglebetweentheunknownpointandtwoormoreknownpoints.d.EachNAVSTARsatelliteisapproximately50meterswideandweighsapproximately90kg.Exercises1.WriteT(True)orF(False)besidethefollowingstatementsaboutthetext.a.GPSusescomputertechnologytoenableaterrestrialterminaltodetermineitspositionontheEarth.b.GPSreceiversdothisbymeasuringthesignalsfromonlyonesatellitessimultaneouslyanddeterminingtheirpositionusingthetimingofthesesignals.c.Trilaterationistheprocessofdeterminingthepositionofanunknownpointbymeasuringthetemperatureofthesidesofanimaginarytrianglebetweentheunknownpointandtwoormoreknownpoints.d.EachNAVSTARsatelliteisapproximately50meterswideandweighsapproximately90kg.FFFFExercises1.WriteT(True)orF(False)besidethefollowingstatementsaboutthetext.e.InorderforGPStrackingtowork,itisnecessarytohaveaccesstotheGlobalPositioningSystembuthaveaGPSreceiverf.IntheGPSsystem,thetwoknownpointsareprovidedbyoneGPSsatellites.g.TheGPSreceiverisabletoreceivesignalsthataretransmittedbystarsorbitingoverhead.h.EventhesesatellitetransmissionsarereceivedbytheGPSreceiver,locationandotherinformationsuchasspeedanddirectioncannotbecalculated.Exercises1.WriteT(True)orF(False)besidethefollowingstatementsaboutthetext.e.InorderforGPStrackingtowork,itisnecessarytohaveaccesstotheGlobalPositioningSystembuthaveaGPSreceiverf.IntheGPSsystem,thetwoknownpointsareprovidedbyoneGPSsatellites.g.TheGPSreceiverisabletoreceivesignalsthataretransmittedbystarsorbitingoverhead.h.EventhesesatellitetransmissionsarereceivedbytheGPSreceiver,locationandotherinformationsuchasspeedanddirectioncannotbecalculated.FFFFExercises2.Matchthefollowingtermstoappropriatedefinitionorexpression.a.GPSb.CDMAc.orbitalperiodof11hoursand58minutesd.GPSsystemisdividedinto1.Space,ControlandUserSegment2.CodeDivisionMultipleAccess3.GlobalPositioningSystem4.orbitstheEarthtwiceeachdayExercises2.Matchthefollowingtermstoappropriatedefinitionorexpression.a.GPSb.CDMAc.orbitalperiodof11hoursand58minutesd.GPSsystemisdividedinto1.Space,ControlandUserSegment2.CodeDivisionMultipleAccess3.GlobalPositioningSystem4.orbitstheEarthtwiceeachdayExercises3.Fillinthemissingwordsaccordingtothetext.a.Inordertomeasurethetimedelaybetween

and

,thesatellitesendsarepeating1,023bitlongpseudorandomsequence;thereceiverconstructsanidenticalsequenceandshiftsituntilthe

match.b.Thesesatellitesconstantlytransmitanidentifying

.c.TheGPSreceivermeasuresthe

toeachGPSsatellitebymeasuringthetimeeachsignaltooktotravelbetweenthe

andtheGPSreceiver.d.GPSuses

operationalsatellites,withanadditional

inorbitasredundantbackup.Exercises3.Fillinthemissingwordsaccordingtothetext.a.Inordertomeasurethetimedelaybetweensatelliteandreceiver,thesatellitesendsarepeating1,023bitlongpseudorandomsequence;thereceiverconstructsanidenticalsequenceandshiftsituntilthetwosequencematch.b.Thesesatellitesconstantlytransmitanidentifyingsignal.c.TheGPSreceivermeasuresthedistancetoeachGPSsatellitebymeasuringthetimeeachsignaltooktot