Trimble R10 - Page 146

TrimbleR10ReceiverWebHelp
L5
).
UTC
UniversalTimeCoordinated.Atimestandardbasedonlocalsolarmeantime
attheGreenwichmeridian.
VRS
VirtualReferenceStation.AVRSsystemconsistsofGNSShardware,software,
andcommunicationlinks.Itusesdatafromanetworkof
basestationsto
providecorrectionstoeachroverthatar emoreaccuratethancorrections
fromasinglebasestation.
TostartusingVRScorrections,theroversendsitspositiontotheVRSserver.
TheVRSserverusesthebasestationdatatomodelsystematicerrors(suchas
ionosphericnoise)attherover
position.ItthensendsRTCMcorrection
messagesbacktotherover.
WAAS
WideAreaAugmentationSystem.WAASwasestablishedbytheFederal
AviationAdministration(FAA)forflightandapproachnavigationforcivil
aviation.WAASimprovestheaccuracyandavailabilityofthebasicGNSS
signalsoveritscoveragearea,whichincludesthecontinentalUnitedStates
andoutlyingpartsofCanadaandMexico.
The
WAASsystemprovidescorrectiondataforvisiblesatellites.Corrections
arecomputedfromgroundstationobservationsandthenuploadedtotwo
geostationarysatellites.ThisdataisthenbroadcastontheL1frequency,and
istrackedusingachannelontheGNSSreceiver,exactlylikeaGNSSsatellite.
UseWAASwhenother
correctionsourcesareunavailable,toobtaingreater
accuracythanautonomouspositions.FormoreinformationonWAAS,refer
totheFAAwebsiteat
http://gps.faa.gov.
The
EGNOSserviceistheEuropeanequivalentandMSASistheJapanese
equivalentofWAAS.
WGS‐84
WorldGeodeticSystem1984.SinceJanuary1987,WGS‐84hassuperseded
WGS‐72asthe
datumusedbyGPS.
TheWGS‐84datumisbasedonthe
ellipsoidofthesamename.
