User's Manual

D.Glossary
N72GNSSReferenceReceiverUserGuidePage64
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,and
multipatherrors.
ephemeris/
ephemerides
Alistofpredicted(accurate)positionsorlocationsof
satellite s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GPS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datausing
30‐secondepochsmeansloadingev eryalternatemeasurement.
firmware Theprograminsidethereceiverthatcontrolsreceiver
operationsandhardw are.
GLONASS GlobalOrbitingNavigationSatelliteSystem.GLONASSisaSovietspace‐based
navigationsystemcomparabletotheAmericanGPSsystem.Theoperational
systemconsistsof21operationaland3non‐operationalsatellite sin3orbit
planes.
GNSS GlobalNavigationSatelliteSys tem.
GSOF GeneralSerialOutputFormat.A
Trimbleproprietarymessageformat.
HDOP HorizontalDilutionofPrecision.HDOPisaDOPvaluethatindicatestheaccuracy
ofhorizontalmeasurements.OtherDOPvaluesincludeVDOP(verticalDOP)and
PDOP(PositionDOP).
UsingamaximumHDOPisidealforsituationswhereverticalprecisionisnot
particularlyimportant,andyourpositionyield
wouldbedecreasedbythevertical
componentofthePDOP(forexample,ifyouarecollectingdataundercanopy).
L1 TheprimaryL‐bandcarrierusedbyGPSsatellitestotransmitsatellitedata.
L2 ThesecondaryL‐bandcarrierusedbyGPSsatellitestotransmitsatellitedata.
L5 The
thirdL‐bandcarrierusedbyGPSsat ellitestotransmitsatellitedata.L5will
provideahigherpowerlevelthantheothercarriers.Asaresult,acquiringand
trackingweaksignalswillbeeasier.
MSAS MTSATSatellite‐BasedAugmentationSystem.Asatellite‐basedaugmentation
system(SBAS)thatprovidesafree‐to
‐airdifferentialcorrectionserviceforGPS.
MSASistheJapaneseequivalentofWAAS,whichisavailableintheUnitedStates.
multi‐frequency
GPS
Atypeofreceiverthatusesmultiplecarrierphasemeasurements(L1,L2,andL5)
fromdifferentsatellitefrequencies.
multipath Interference,similartoghostsonatelevisionscreen
thatoccurswhenGPSsignals
arriveatanantennahavingtraverseddifferentpaths.Thesignaltraversingthe
longerpathyieldsalargerpseudorangeestimateandincreasestheerror.Multiple
pathscanarisefromreflectionsoffthegroundoroffstructuresneartheantenna.
NMEA NationalMarineElectronicsAssociation.NMEA0183defines
thestandardfor
interfacingmarineelectronicnavigationaldevices.Thisstandarddefinesanumber
of'strings'referredtoasNMEAstringsthatcontainnavigationaldetailssuchas
positions.MostCHCGPSreceiverscanoutputpositionsasNMEAstrings.
PDOP PositionDilutionofPrecision.PDOPisaDOPvaluethatindicatesthe
accuracyof