Performance Analysis of QZSS Centimeter Level Augmentation...
Transcript of Performance Analysis of QZSS Centimeter Level Augmentation...
PerformanceAnalysisofQZSSCentimeterLevelAugmentationServices(CLAS)ForStanfordPNT2019,Stanford,California
Po-ChunChiu,Shuo-JuYehandShau-ShiunJan
2019/10/29
InstituteofAeronauticsandAstronautics,NationalChengKungUniversity,Taiwan.
Outline
• Quasi–ZenithSatelliteSystem• MotivationsandObjectives• CentimeterLevelAugmentationService• L6DMessageStructure• SubtypesinL6Message
• CLASMessageAnalysis• CLASAidingPrecisePointPositioning• Conclusions• FutureWork
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Quasi–ZenithSatelliteSystem(QZSS)
• RegionNavigationSatelliteSystem• 1geostationaryequatorialorbit(GEO)satelliteand3Quasi-Zenithorbit(QZO)satellitesareincludedinQZSS.
• EastAsiaandAustraliaarea• L1,L2,L5,L6Signal• CentimeterLevelAugmentationService(CLAS)
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CentimeterLevelAugmentationService
• CLASsupportsRTK-PPPrealtimeusers.Itisdesignedtoimprovepositioningtocentimeterlevel.
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ObservationNetworks&Station
AugmentationDataGeneration&Transition
QZSSSatellite
L6Signal
LandSurvey ITConstruction ITAgriculture
Observation Space Representation (OSR)
State Space Representation (SSR)
Motivations
• QZSSsignalcanbereceivedinTaiwananytimeinadayandhasaverygoodperformanceinelevation.
• Theelevationofeachsatelliteisabove60°for12hoursperday.
5 Takeyasu Sakai & Satoshi Kogure (2018, September) QZSS Update. ION2018+, Miami, Florida
Taiwan
Objectives
• TaiwanlocatesattheedgeofCLASserviceboundary.
• ApreliminaryevaluationsofthePPPmethodwithCLASserviceareprovided.
• SatelliteDatafromIGSstationandCLASdatafromQZSSwebsiteareused.
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L6DMessageStructure
• L6DMessageStructure• 2000bps• 6subframesin30seconds• Eachsubframetakes5seconds
Header49bits
Reed-SolomonCode256bits
DataPart1695bits
2000bits/sec
SubtypeN1 n1bits
SubtypeN2 n2bits
SubtypeNk nkbits
Header Reed-SolomonCodeDataPart5
5DataPartsin1Subframes
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…
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Header Reed-SolomonCodeDataPart1
2000bits
L6DMessageStructure
• Correctionscontainedin11Subtypeswillbetransmittedin6subframes.
• NetworkIDisusedtoidentifyspecificlocalcorrectionmessages.
Subframe 1 2 3 4 5 6
Subtype 1~9,11 3,6,8,9,11 3,6,8,9,11 3,6,8,9,11 3,6,8,9,11 3,6,8,9,11
NetworkID
12,2 3,4,14 5,6,15,16 7,8,17,18 9,10,19 11,1
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CLASNetwork
• Formedby19Networks.• EachNetworkisformedbyseveralgridpoints.Thereare231gridpointsintotal.Gridpointsindicatethepositionofaobservationstation.
• Thesestationsaresettocollectlocaldataandreportresultforfurtheraugmentationproduction.
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345 6 7
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15 16 17 18
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SubtypesinL6Message
• Subtype1:ThissubtypeindicatestheincludedsatellitesandsignalsintheCLASmessage.
• Network-independentSubtype:Subtype2,3,4,5,7• Onlytheinformationfromsubtype1isusedtodecodethesesubtypes.
MessageHeader CellMaskSatelliteMask SignalMask
MessageHeader
DataforSatellite/Signal1
DataforSatellite/SignalN
…
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SubtypesinL6Message
• Network-DependentSubtype:Subtype6,8,9,11• Dateincludeinthesesubtypeswillincrease/decreasewiththequantityofgridpointsineachNetwork.
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MessageHeader
Grid1dataforSatellite1
Grid𝑁datafordataforSatellite1
Grid1dataforSatellite𝑀
Grid𝑁datafordataforSatellite𝑀
…
…
…
NetworkID
CorrectionsinL6Message
SubtypeCorrection
1 2 3 4 5 6 7 8 9 10 11
CellMask √
OrbitCorrection √ ●
GNSSClockCorrection √ ●
Code/PhaseBias √ √ ●
IonosphereSlantDelay ● ●
TroposphereDelay ●
Integrity √
TBD * 12
√ forGeneralData,30secondsinterval; ● forNetworkData,5secondsinterval
AvailabilityofCLAS
• Date:2018/11/28• Time:0:00~23:59• DataSize:164.8MB• Location:Nakatane,Japan
• Atleast6GPSSatellitesaresupportedin95%ofaday.
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OrbitCorrection
• Source:Subtype2,11• Date:2018/11/28• Satellite:G06• UserAlgorithm: 𝑟↓𝑐𝑜𝑟𝑟𝑒𝑐𝑡 = 𝑟↓𝑒𝑝ℎ −𝛿𝑟↓𝐶𝐿𝐴𝑆 • Radial,Cross,andAlongvectorsagainstuserpositionwillhelpcalculation.
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NoCLASSupportforthisSatellite
GNSSClockCorrection
• Source:Subtype3,11• Date:2018/11/28• Satellite:G06• UserAlgorithm: 𝑡↓𝑐𝑜𝑟𝑟𝑒𝑐𝑡 = 𝑡↓𝑏𝑟𝑜𝑎𝑑𝑐𝑎𝑠𝑡 −𝛿𝑡↓𝐶𝐿𝐴𝑆
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GNSSCode/PhaseBias
• Source:Subtype4,5,6• Date:2018/11/28• Satellite:G06• UserAlgorithm: 𝜌↓𝑐𝑜𝑟𝑟𝑒𝑐𝑡,𝑐𝑜𝑑𝑒/𝑝ℎ𝑎𝑠𝑒 = 𝜌↓𝑐𝑜𝑑𝑒/𝑝ℎ𝑎𝑠𝑒 +𝛿𝜌↓𝐶𝐿𝐴𝑆,𝑐𝑜𝑑𝑒/𝑝ℎ𝑎𝑠𝑒 • Mappingbytheline-of-sightvectorfromuserpositiontothesatellite
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IonosphereSlantDelayCorrection
• Source:Subtype8,9• Date:2018/11/28• Polynomialpartandresidualpart
• Ionosphereslantdelayatuserpositioniscomputedbyinterpolatingtheoneonreferencegrids.
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TroposphereDelayCorrection
• Source:Subtype9• Date:2018/11/28• Troposphereverticaldelayvariationsarecomputedbyinterpolatingorextrapolatingthedataonthereferencegrid.
• Amappingfunctionisnecessaryforfurtherapplication.
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CLASAidingPrecisePointPositioning
• Date:2018/11/28• Accuracylevel:1meter• ConvergenceImprovement:901stepochto160thepoch
• Reductionisabout83%originalneededepoch.
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901st 160th
CLASAidingPrecisePointPositioning Date:2018/11/28Accuracylevel:0.3meter
Date:2019/03/04Accuracylevel:0.3meter
1730th
867th
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1293rd
582nd
Reduction:50%
Conclusions
• CLASbinarydatadecoderconsideredasaSSRtoOSRconvertor.• CLASuseralgorithmarecompletedandcanassistpositioningmethods.
• CombinationofPPPandCLASisimplemented.• ConvergencetimeimprovementagainstresultbeforeapplyingCLAS:• About50%for0.3meteraccuracylevel• About83%for1meteraccuracylevel
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FutureWork
• UsingSoftware-DefinedReceiver(SDR),theQZSSL6canbeobtainedthroughacquisition,trackinganddemodulationprocess.WewillcompletetheworkandapplyCLASdatatolocalpositioning.
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Reference
• Takeyasu Sakai & Satoshi Kogure (2018, September ). QZSS Update. ION2018+, Miami, Florida. Retrieved from https://www.ion.org/publications/abstract.cfm?articleID=15837
• Cabinet Office(2018). Quasi-Zenith Satellite System Interface. Specification: Centimeter Level Augmentation Service. Retrieved from https://qzss.go.jp/en/technical/ps-is-qzss/ps-is-qzss.html
• T. Takasu(2019). RTKlib(v2.4.3). Retrieved from http://www.rtklib.com/rtklib.htm
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ThankYou! Po-ChunChiu