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1、英文翻译IntroductiontotheGlobalPositioningSystemWhatisGPS?TheGlobalPositioningSystem(GPS)isalocationsystembasedonaconstellationofabout24satellitesorbitingtheearthataltitudesofapproximately11,000miles.GPSwasdevelopedbytheUnitedStatesDepartmentofDefense(DOD),foritstremendousapplicationas
2、amilitarylocatingutility.TheDOD'sinvestmentinGPSisimmense.Billionsandbillionsofdollarshavebeeninvestedincreatingthistechnologyformilitaryuses.However,overthepastseveralyears,GPShasproventobeausefultoolinnon-militarymappingapplicationsaswell.GPSsatellitesareorbitedhighenoughtoavoidt
3、heproblemsassociatedwithlandbasedsystems,yetcanprovideaccuratepositioning24hoursaday,anywhereintheworld.UncorrectedpositionsdeterminedfromGPSsatellitesignalsproduceaccuraciesintherangeof50to100meters.Whenusingatechniquecalleddifferentialcorrection,userscangetpositionsaccuratetowith
4、in5metersorless.Today,manyindustriesareleveragingofftheDOD'smassiveundertaking.AsGPSunitsarebecomingsmallerandlessexpensive,thereareanexpandingnumberofapplicationsforGPS.Intransportationapplications,GPSassistspilotsanddriversinpinpointingtheirlocationsandavoidingcollisions.Farmersc
5、anuseGPStoguideequipmentandcontrolaccuratedistributionoffertilizersandotherchemicals.Also，GPSisusedforprovidingaccuratelocationsandasanavigationtoolforhikers,huntersandboaters.ManywouldarguethatGPShasfounditsgreatestutilityinthefieldofGeographicInformationSystems(GIS).Withsomeconsi
6、derationforerror,GPScanprovideanypointonearthwithauniqueaddress(itspreciselocation).AGISisbasicallyadescriptivedatabaseoftheearth(oraspecificpartoftheearth).GPStellsyouthatyouareatpointX,Y,ZwhileGIStellsyouthatX,Y,Zisanoaktree,oraspotinastreamwithapHlevelof5.4.GPStellsusthe"where".
7、GIStellsusthe"what".GPS/GISisreshapingthewaywelocate,organize,analyzeandmapourresources.Trilateration-HowGPSDeterminesaLocation？Inanutshell,GPSisbasedonsatelliteranging-calculatingthedistancesbetweenthereceiverandthepositionof3ormoresatellites(4ormoreifelevationisdesired)andthenapp
8、lyingsomegoodoldmathematic
