Trimble R10 - Page 141

TrimbleR10ReceiverWebHelp
rover
withdatacollectedsimultaneouslyatabasestation.Becausethebase
stationisonaknownlocation,anyerrorsindatacollectedatthebasestation
canbemeasured,andthenecessarycorrectionsappliedtotheroverdata.
Differentialcorrectioncanbedoneinreal‐time,orafterthedataiscollected
by
postprocessing.
differentialGPS
See
real‐timedifferentialGPS.
DOP
DilutionofPrecision.AmeasureofthequalityofGNSSpositions,basedon
thegeometryofthesatellitesusedtocomputethepositions.Whensatellites
arewidelyspacedrelativetoeachother,theDOPvalueislower,andposition
accuracyisgreater.Whensatellitesareclosetogetherinthesky,
theDOPis
higherandGNSSpositionsmaycontainagreaterleveloferror.
PDOP(PositionDOP)indicatesthethree‐dimensionalgeometryofthe
satellites.OtherDOPvaluesinclude
HDOP(HorizontalDOP)andVDOP
(VerticalDOP),whichindicatetheaccuracyofhorizontalmeasurements
(latitudeandlongitude)andverticalmeasurementsrespectively.PDOPis
relatedtoHDOPandVDOPasfollows:PDOP²=HDOP²+VDOP².
dual‐frequencyGPS
Atypeofreceiverthatusesboth
L1andL2signalsfromGPSsatellites.A
dual‐frequencyreceivercancomputemoreprecisepositionfixesoverlonger
distancesandundermoreadverseconditionsbecauseitcompensatesfor
ionosphericdelays.
EGNOS
EuropeanGeostationaryNavigationOverlayService.ASatellite‐Based
AugmentationSystem(SBAS)thatprovidesafree‐to‐airdifferential
correctionserviceforGNSS.EGNOSistheEuropeanequivalentof
WAAS,
whichisavailableintheUnitedStates.
elevationmask
Theanglebelowwhichthereceiverwillnottracksatellites.Normallysetto
10degreestoavoidinterferenceproblemscausedbybuildingsandtrees,
atmosphericissues,andmultipatherrors.
ellipsoid
Anellipsoidisthethree‐dimensionalshapethatisusedasthebasisfor
mathematicallymodelingtheearth’ssurface.Theellipsoidisdefinedbythe
lengthsoftheminorandmajoraxes.Theearth’sminoraxisisthepolaraxis
andthemajoraxisistheequatorialaxis.
EHT
Heightaboveellipsoid.
ephemeris/ephemerides
Alistofpredicted(accurate)positionsorlocationsofsatellitesasafunction
oftime.Asetofnumericalparametersthatcanbeusedtodeterminea
satellite’sposition.Availableasbroadcastephemerisoraspostprocessed
preciseephemeris.
epoch
ThemeasurementintervalofaGNSSreceiver.Theepochvariesaccordingto
themeasurementtype:forreal‐timemeasurementitissetatonesecond;for
postprocessedmeasurementitcanbesettoarateofbetweenonesecond
andoneminute.Forexample,ifdataismeasuredevery15
seconds,loading