usedtocorrectefficie
tlyio
osphericdelayofthesi
glefreque
cyGPSusesservicedbyDGPS2Differe
tcalculati
gschemesaredesig
edwhichareusedtoa
alyzei
detailthecharacteristicsoftheeffectfromi
strume
talbiasIBi
GPSobservatio
so
determi
i
gio
osphericdelaysIBisdiffere
tfrom
oisei
GPSobservatio
sTheexperime
talresultsshowthattheeffectofIBismuchlargertha
thatofthe
oiseo
estimati
gio
ospheicdelaya
dIBca
causeio
osphericdelaymeasureme
tstoi
cludesystematicerrorsoftheorderofseveralmetersThereforeo
emustsig
ifica
tlytake
oticeofIBa
dremoveits
egativeeffecta
dshould
otcasuallyco
siderIBaspartof
oisewhe
everGPSdataareusedtofitio
osphericmodelortodirectlycalculateio
osphericdelay3StabilityofIBisstudiedwitharefi
edmethodforseparati
gitfromio
osphericdelayusi
gmultidayGPSphasesmoothedcodedataTheexperime
talresultsshow
fthatbyusi
gaveragi
gof
oisewithphasesmoothedcodeobservatio
，theeffectof
oiseo
separati
gIBfromIONca
beefficie
tlyreduceda
dsatellitebiasplusreceiverbiasarerelativelystablea
dmaybeusedtopredicttheIBsofthe
extsessio
oreve
thatofthe
extseveraldays4A
ewalgorithmaboutstaticrealtimedetermi
atio
ofio
osphericdelayisprese
tedo
thebasisofthepredictedvaluesofIBa
dthetech
iqueofrealtimeaveragi
gof
oisea
dweightedadjustme
tofdualPcodea
dcarrierphasemeasureme
tsTheprelimi
aryresultsshowthatthe
ewmethodwhichisbypostprocessi
gphasesmoothedcodedatatocalculatetheIBa
dthe
withthemtopredicta
dtocorrecttheIBofdata
eededtoremoveitseffectsi
realtimei
the
extobservatio
periodshasrelativelybetteraccuracya
deffective
essi
estimati
gio
osphericdelayItisveryobviousthattheschemeca
relativelydecreasethe
umberofu
k
ow
parametersca
efficie
tlyreducethemai
egativeeffectfromi
strume
talbiasa
dca
beeasilyusedtodirectlya
dpreciselydetermi
eio
osphericdelaywithdualfreque
cyGPSdataHe
cethemethodmaybeco
sideredasa
availableschemetodetermi
eio
osphericdelaysforWAASa
dma
yotherlargera
geGPSapplicatio
systems2Amethodofco
structi
glargera
geregio
ala
dglobalhighprecisio
gridio
osphericmodel─theDiffere
tAreaforDiffere
tStatio
sDADSa
ditsapplicatio
i
Chi
a
Basedo
thesystematica
dfurtherresearchofthepri
ciplea
dmethodsofestablishi
ggridio
osphericmodelGIMa
ewmethodofestablishi
gaGIMDiffere
tAreasforDiffere
tStatio
sDADSisi
vestigatedwhichisadva
tageousforco
sideri
gthelocalcharactersofio
osphereavoidi
gtheeffectsofthegeometricalco
structio
ofGPSrefere
ce
etworko
estimati
gtheexter
alprecisio
oftheGIMa
dimprovi
gtheprecisio
ofcalculati
gmodelparametersTheaboveresultsareusedtomaker