Overview of GNSS biases - Portal · Overview of GNSS biases Stefan Schaer Swiss Federal Office of Topography (swisstopo) / CODE@AIUB ... (TGD) as broadcast by the GPS • Parameters

armasuisseSwiss Federal Office of Topography swisstopo

Overview of GNSS biases

Stefan Schaer

Swiss Federal Office of Topography (swisstopo) / CODE@AIUB

2Swiss Federal Office of Topography swisstopoWorkshop on GNSS Biases, Uni Bern, 18-19 January 201 2

Contents

• Introduction• GPS/GLONASS differential code biases• CODE’s DCB specialties• GLONASS ambiguity resolution• Intersystem phase biases• GLONASS-GPS station-specific intersystem translations• IGS ANTEX model

Not addressed in this overview presentation:• GLONASS interfrequency code biases• Phase biases relevant to undifferenced ambiguity resolution


Contents

• Introduction

• GPS/GLONASS differential code biases• CODE’s DCB specialties• GLONASS ambiguity resolution• Intersystem phase biases• GLONASS-GPS station-specific intersystem translations• IGS ANTEX model


What is a bias?

Source: www.thefreedictionary.com/bias


Sign convention

• bias = estimator – (true or unbiased) parameter

• bias = observation – true or unbiased observation• observation = true observation + bias• true observation = observation – bias• Numerical example:

- ground truth: 11- observed: 7- bias (or error): -4

true observation

observation bias


Sign convention as given for IONEX


GNSS biases?

• A prominent example is: GPS group delays (TGD) as broadcast by the GPS

• Parameters that might be considered as nuisance (or bias) parameters- ionosphere

- troposphere- antenna - clock

have in fact a physical meaning (and are useful for particular applications)

• Our main focus is on: biases with respect to specif ic GNSS observables


Receiver classification

• The following code (pseudorange) observables are available from GPS: C/A (=C1), P1(Y1), P2(Y2), and C2 (for the Block IIR-M constellation).

• In the presence of Anti-Spoofing (AS), P-codes P1, P2 are encrypted for non-authorized users to Y1, Y2.

• We have to distinguish between three receiver classes (in terms of the code tracking technology):- P1/P2: C1, P1, P2- C1/X2: C1, X2=C1+(P2-P1) - C1/P2: C1, P2

• C1/X2 receiver models are identified as cross-correlation (CC) receivers. Prominent examples are Rogue and Trimble 4000 models.

• The operation of CC receivers depends on the AS state. It is assumed here that AS is always on (!).

• The latest generations of Leica, Novatel, Trimble receivers belong to the C1/P2 receiver class (at least in terms of GPS).


Contents

• Introduction



Instrumental code biases

• Instrumental biases, BC1, BP1, BP2, BC2, are present with respect to C1, P1, P2, C2. These biases are not accessible (in the absolutesense).

• It is common to address the following differences of code biases:- P1-P2,- P1-C1, and- P2-C2 differential code bias (=DCB).

• By convention, precise satellite clock corrections contain a specific linear combination of P1 and P2 satellite biases, specifically the ionosphere-free LC: 2.55·BP1-1.55·BP2(+B0).

• It is obvious that code tracking data from both the C1/X2 and the C1/P2 receiver class must be corrected in order to achieve full consistency with P1/P2 data, or precise satellite clock information.

• Non-separability: satellite and receiver biases are generally not separable.


How to Use P1-P2 and P1-C1 Satellite DCB Informatio n

The following table gives the corrections due to satellite-specific P1-P2 and P1-C1 DCB values for the most important linear combinations derived from various combinations of code observable types:

Single-freq.

ClockIono.

Amb. res.

Determination methods:• P1-P2: Iono. / Abs. receiver cal.• P1-C1: Diff. / Clock / Amb. res.


CODE’s GPS P1-P2 DCB monthly solution, computed for December 2011


GPS broadcast P1-P2 DCB information, collected in December 2011 (+5.47 ns)


CODE’s GPS/GLONASS P1-P2 DCB monthly solution, computed for December 2011


CODE’s GPS P1-P2 DCB monthly solution, computed for December 2011


CODE’s GLONASS P1-P2 DCB monthly solution, computed for December 2011


GNSS global ionosphere map (GIM) information as derived by CODE


GIM information every 2 hours: CODE(CODG/CORG/COPG)


GIM information: GPS broadcast (Klobuchar)(GPSG)


GIM information: CODE Klobuchar-style (CKMG)


GNSS P1-P2 DCB retrieval affected by solar cycle


CODE’s GPS P1-C1 DCB monthly solution, computed for December 2011 (as provided to IGS)


CODE’s GPS P1-C1 DCB monthly solution, computed for December 2011 (directly from RINEX)


GPS receiver classes commonly distinguished:

P1/P2: C1 P1 P2

C1/P2: C1 P2C1/X2: C1 X2

Indirect and direct GPS P1-C1 DCB determination (1/3)



P1/P2: C1 P1 P2

C1/P2: C1 P2C1/X2: C1 X2




P1/P2: C1 P1 P2

C1/P2: C1 P2C1/X2: C1 X2



Direct GNSS DCB estimation for P1-C1 and P2-C2 based on RINEX data (using RNXSMT)

• P1-C1 and P2-C2 observation differences are analyzed file by file (typically station by station for a particular day) and stored for:- overall combination- combinations may be actually recalled/retrieved for:

� selected receiver types� selected receiver groups� all considered receivers/stations (=overall combination)

• Sophisticated outlier detection scheme using quantities responding to IQR (interquartile range IQR=Q0.75-Q0.25) � just one scalar quantity to be selected to cope with observation data with most various noise levels and characteristics, respectively

• Overall (LS) combination performed (with an outlier detection scheme concerning station-specific, or file-specific DCB determinations)


CODE’s GNSS P1-C1 DCB monthly solution, computed for December 2011 (directly from RINEX)




CODE’s GLONASS P1-C1 DCB monthly solution, computed for December 2011 (directly from RINEX)


CODE’s GNSS P2-C2 DCB monthly solution, computed for December 2011 (directly from RINEX)




CODE’s GLONASS P2-C2 DCB monthly solution, computed for December 2011 (directly from RINEX)


GPS/GLONASS differential code bias (DCB) products regularly generated at CODE (1/2)

2125.7

# R satellitesRange (ns)

GPS clock analysis314.0

P1C1(Primary product)

GPS Melbourne-Wübbena ambiguity resolution

314.0

P1C1(Extra product)

GPS/GLONASS ionosphere analysis

12553.1

27860.8

3112.3

P1P2

Generated in:# R stationsRange (ns)

# G stationsRange (ns)

# G satellitesRange (ns)

Product


GPS/GLONASS differential code bias (DCB) products regularly generated at CODE (2/2)

GNSS direct determination

93.5

263.1

1914.0

80.9

P2C2

225.1

2125.7

# R satellitesRange (ns)

GPS clock analysis314.0

P1C1(Primary product)

GNSS direct determination

22 (95)3.8

11 (214)4.5

314.0

P1C1(Complementary product)

GPS Melbourne-Wübbena ambiguity resolution

314.0

P1C1(Extra product)

GPS/GLONASS ionosphere analysis

12553.1

27860.8

3112.3

P1P2

Generated in:# R stationsRange (ns)

# G stationsRange (ns)

# G satellitesRange (ns)

Product


Comparison of GPS P1-C1 DCB results from indirect and direct determination (1/3)






Comparison of P2-C2 DCB results for the GPS Block IIR-M satellites (1/3)






Comparison of P2-C2 DCB results for the GLONASS-M satellites (1/2)


Comparison of P2-C2 DCB results for the GLONASS-M satellites (2/2)


GNSS DCB reprocessing from RINEX

• New BPE process (DCBIONO) developed- 10 programs upgraded to latest standards of the Bernese SW - will soon replace old DCB combination, ionosphere prediction,

and other related procedures- includes processing step for extraction of GPS and GLONASS

P1-C1 and P2-C2 DCB values (using the direct determination method)

- corresponding (combined) DCB results are computed and stored daily for:� each station� receiver types� receiver groups� overall combination

• Reprocessing as of 1990 (21 years of data from CODE’s IGS database)

• Implementation of P2-C2 DCB retrieval (using PPP) for “P2-or-C2”stations might be a feasible option


Statistics on GNSS DCB reprocessing from RINEX


Statistics on GNSS DCB reprocessing from RINEX


GPS-GLONASS receiver clock offsets (when using GPS/GLONASS broadcast clock information), computed for days 009, 010, 011 of year 2012 (1/3)






Receivers not providing P1&C1 for GLONASS

Receiver type P1&C1 Remark-----------------------------------ASHTECH Z18 0% P1=C1JAVAD TRE_G3T DELTA 100%JPS EGGDT 100%JPS EUROCARD 100%JPS E_GGD 100%JPS LEGACY 100%LEICA GRX1200+GNSS 0% C1LEICA GRX1200GGPRO 0% C1NOV OEMV3 0% C1TPS EGGDT 100%TPS EUROCARD 100%TPS E_GGD 100%TPS GB-1000 100%TPS LEGACY 100%TPS NETG3 100%TPS ODYSSEY_E 100%TRIMBLE NETR5 31% C1 or P1&C1 (C1&C2 for BNDY!)TRIMBLE NETR8 100%


Contents

• Introduction



Verification of receiver tracking technology using the Bernese Software

================================================================================

PART 6: VERIFICATION OF RECEIVER TRACKING TECHNOLOGY

================================================================================

STATION NAME MULTIPLIER RMS ERROR SUGGESTED RECEIVER TYPE GIVEN RECEIVER NAME / TYPE MATCH

----------------------------------------------------------------------------------------------------------------

BRUS 13101M004 -G -0.224 0.043 P1/P2 5.242 28.666 ASHTECH Z-XII3T P1/P2 OK

FFMJ 14279M001 -G -0.105 0.051 P1/P2 2.045 21.578 JPS LEGACY P1/P2 OK

MATE 12734M008 -G 0.874 0.048 C1/X2 2.637 18.312 TRIMBLE 4000SSI C1/X2 OK

ONSA 10402M004 -G -0.104 0.041 P1/P2 2.536 26.943 ASHTECH Z-XII3 P1/P2 OK

PTBB 14234M001 -G -0.124 0.048 P1/P2 2.579 23.352 ASHTECH Z-XII3T P1/P2 OK

VILL 13406M001 -G -0.062 0.044 P1/P2 1.404 24.048 ASHTECH Z-XII3 P1/P2 OK

ZIMJ 14001M006 -G 0.057 0.048 P1/P2 1.195 19.598 JPS LEGACY P1/P2 OK

ZIMM 14001M004 -G 1.131 0.047 C1/X2 2.788 24.083 TRIMBLE 4000SSI C1/X2 OK

Excerpt of a PPP BPE processing summary file (PPP03139.PRC):


How to Use P1-P2 and P1-C1 Satellite DCB Informatio n

The following table gives the corrections due to satellite-specific P1-P2 and P1-C1 DCB values for the most important linear combinations derived from various combinations of code observable types:

Single-freq.

ClockIono.

Amb. res.


Contents

• Introduction



Single-difference ambiguity bias term• Illustration of the single-difference (SD) ambiguity bias term,

as introduced by Habrich (1999), to be proportional to the single-difference ambiguity initialization bias (and proportional to the GLONASS frequency channel difference i–j):


GNSS ambiguity resolution at CODE

• Up to 6000km (3000km in a first POD step): Melbourne-Wübbenawidelane and narrowlane ambiguity resolution restricted to GPS only

• Up to 2000km: Quasi-Ionosphere-Free (QIF) L1&L2 AR for GPSand for GLONASS SD ambiguities with the same frequency channel numbers

• Up to 200km: Phase-based widelane AR for GPS and GLONASS, with retrieval of GLONASS SD ambiguity initialization biases; narrowlane AR for GPS and GLONASS1 considering the previously extracted SD bias values

• Up to 20km: Direct L1&L2 AR for GPS and GLONASS(1), retrieval of GLONASS SD ambiguity initialization biases

• New: Ambiguity verification (AMBVER) BPE processing step

1Self-calibrating ambiguity resolution step


Ambiguity resolution summary (e.g. AMB113030.SUM):================================================================================AMBIGUITY RESOLUTION (L1&L2)================================================================================

File Sta1 Sta2 Length Before After Res Sys Max/RMS L1 Receiver 1 Receiver 2(km) #Amb (mm) #Amb (mm) (%) (L1 Cycles)

----------------------------------------------------------------------------------------------------------------------0AMT3030 MAT1 MATE 0.011 114 1.5 4 1.5 96.5 G 0.121 0.025 TRIMBLE 4000SSI LEICA GRX1200GGPRO #AR_L120JT33030 THU2 THU3 0.000 148 0.8 0 0.8 100.0 G 0.044 0.005 JPS LEGACY ASHTECH UZ-12 #AR_L120KUO3030 UNBJ UNBN 0.000 168 0.5 6 2.8 96.4 G 0.252 0.055 TPS LEGACY NOV OEMV3 #AR_L120KUO3030 UNBJ UNBN 0.000 102 0.5 0 2.8 100.0 R 0.043 0.014 TPS LEGACY NOV OEMV3 #AR_L120KUO3030 UNBJ UNBN 0.000 270 0.5 6 2.8 97.8 GR 0.252 0.044 TPS LEGACY NOV OEMV3 #AR_L120KUU3030 UNBJ UNBT 0.000 100 0.6 0 0.8 100.0 G 0.090 0.015 TPS LEGACY TPS NETG3 #AR_L120KUU3030 UNBJ UNBT 0.000 100 0.6 0 0.8 100.0 R 0.034 0.011 TPS LEGACY TPS NETG3 #AR_L120KUU3030 UNBJ UNBT 0.000 200 0.6 0 0.8 100.0 GR 0.090 0.013 TPS LEGACY TPS NETG3 #AR_L120LUO3030 UNB3 UNBN 0.000 172 0.7 5 3.0 97.1 G 0.258 0.059 TRIMBLE NETR5 NOV OEMV3 #AR_L120LUO3030 UNB3 UNBN 0.000 100 0.7 0 3.0 100.0 R 0.056 0.016 TRIMBLE NETR5 NOV OEMV3 #AR_L120LUO3030 UNB3 UNBN 0.000 272 0.7 5 3.0 98.2 GR 0.258 0.048 TRIMBLE NETR5 NOV OEMV3 #AR_L120SIK3030 IRKJ IRKT 0.004 128 1.2 0 1.3 100.0 G 0.083 0.020 JPS LEGACY ROGUE SNR-8000 #AR_L120WM43030 CRAR MCM4 1.089 154 5.2 2 5.2 98.7 G 0.113 0.017 TPS ODYSSEY_E ASHTECH UZ-12 #AR_L120YJO3030 JOZ2 JOZE 0.084 108 1.4 4 1.5 96.3 G 0.083 0.021 LEICA GRX1200GGPRO TRIMBLE 4000SSI #AR_L12CG0T3030 CAGL CAGZ 0.003 96 1.3 0 1.4 100.0 G 0.134 0.021 TRIMBLE 4700 TPS E_GGD #AR_L12DGD33030 DGAR DGAV 0.000 96 0.6 0 0.6 100.0 G 0.013 0.003 ASHTECH UZ-12 JPS EGGDT #AR_L12FAFI3030 FAIR FAIV 0.038 160 1.6 0 1.7 100.0 G 0.049 0.015 ASHTECH UZ-12 JPS EGGDT #AR_L12FR0L3030 FRDN UNB3 2.332 112 1.9 1 2.1 99.1 G 0.110 0.023 TPS NETG3 TRIMBLE NETR5 #AR_L12FR0L3030 FRDN UNB3 2.332 100 1.9 0 2.1 100.0 R 0.072 0.021 TPS NETG3 TRIMBLE NETR5 #AR_L12FR0L3030 FRDN UNB3 2.332 212 1.9 1 2.1 99.5 GR 0.110 0.022 TPS NETG3 TRIMBLE NETR5 #AR_L12GUUG3030 GUAM GUUG 18.678 84 15.9 4 18.2 95.2 G 0.341 0.122 ASHTECH UZ-12 TRIMBLE NETR5 #AR_L12HAHR3030 HARB HRAO 2.066 94 2.6 0 2.8 100.0 G 0.100 0.022 ASHTECH UZ-12 ASHTECH UZ-12 #AR_L12HM073030 HERS HERT 0.136 102 1.0 4 1.1 96.1 G 0.042 0.010 SEPT POLARX3ETR LEICA GRX1200GGPRO #AR_L12HM073030 HERS HERT 0.136 110 1.0 0 1.1 100.0 R 0.193 0.030 SEPT POLARX3ETR LEICA GRX1200GGPRO #AR_L12HM073030 HERS HERT 0.136 212 1.0 4 1.1 98.1 GR 0.193 0.023 SEPT POLARX3ETR LEICA GRX1200GGPRO #AR_L12KKK43030 KOKB KOKV 0.000 90 0.5 0 0.6 100.0 G 0.020 0.005 ASHTECH UZ-12 JPS EGGDT #AR_L12MJKM3030 MOBJ MOBK 0.000 120 0.6 0 0.7 100.0 G 0.006 0.001 JPS LEGACY JPS EGGDT #AR_L12MJKM3030 MOBJ MOBK 0.000 116 0.6 0 0.7 100.0 R 0.022 0.004 JPS LEGACY JPS EGGDT #AR_L12MJKM3030 MOBJ MOBK 0.000 236 0.6 0 0.7 100.0 GR 0.022 0.003 JPS LEGACY JPS EGGDT #AR_L12MS0B3030 METS METZ 0.001 146 1.0 0 1.1 100.0 G 0.039 0.012 ASHTECH Z-XII3 JPS EUROCARD #AR_L12O20E3030 OHI2 OHI3 0.003 144 1.2 2 1.2 98.6 G 0.041 0.008 JPS E_GGD LEICA GRX1200GGPRO #AR_L12O20E3030 OHI2 OHI3 0.003 128 1.2 0 1.2 100.0 R 0.094 0.017 JPS E_GGD LEICA GRX1200GGPRO #AR_L12O20E3030 OHI2 OHI3 0.003 272 1.2 2 1.2 99.3 GR 0.094 0.013 JPS E_GGD LEICA GRX1200GGPRO #AR_L12P3P43030 PBR2 PBRI 0.012 100 1.2 4 1.2 96.0 G 0.149 0.020 LEICA GRX1200+GNSS LEICA GRX1200+GNSS #AR_L12PMPH3030 PIMO PTAG 11.789 100 12.4 10 13.9 90.0 G 0.347 0.098 ASHTECH UZ-12 LEICA GRX1200GGPRO #AR_L12S2ZI3030 ZIM2 ZIMM 0.019 76 1.4 0 1.4 100.0 G 0.021 0.004 TRIMBLE NETR5 TRIMBLE NETRS #AR_L12SLS43030 SUTH SUTV 0.000 88 0.4 0 0.4 100.0 G 0.012 0.002 ASHTECH UZ-12 JPS EGGDT #AR_L12sLuL3030 TAH1 TAH2 0.000 92 0.3 0 0.3 100.0 G 0.003 0.001 ASHTECH Z-XII3 ASHTECH Z-XII3 #AR_L12TDCB3030 TID1 TIDB 0.000 88 1.0 0 1.1 100.0 G 0.032 0.008 TRIMBLE NETR8 ASHTECH UZ-12 #AR_L12uLTI3030 TAH2 THTI 0.028 82 1.2 0 1.3 100.0 G 0.033 0.010 ASHTECH Z-XII3 TRIMBLE NETR8 #AR_L12WR0M3030 WTZR WTZZ 0.002 98 1.5 4 1.6 95.9 G 0.029 0.009 LEICA GRX1200+GNSS JAVAD TRE_G3TH DELTA #AR_L12WR0M3030 WTZR WTZZ 0.002 116 1.5 0 1.6 100.0 R 0.098 0.022 LEICA GRX1200+GNSS JAVAD TRE_G3TH DELTA #AR_L12WR0M3030 WTZR WTZZ 0.002 214 1.5 4 1.6 98.1 GR 0.098 0.017 LEICA GRX1200+GNSS JAVAD TRE_G3TH DELTA #AR_L12XGTX3030 TIXG TIXI 0.000 144 0.5 0 0.5 100.0 G 0.019 0.003 TPS ODYSSEY_E JPS EGGDT #AR_L12XGTX3030 TIXG TIXI 0.000 120 0.5 0 0.5 100.0 R 0.019 0.003 TPS ODYSSEY_E JPS EGGDT #AR_L12XGTX3030 TIXG TIXI 0.000 264 0.5 0 0.5 100.0 GR 0.019 0.003 TPS ODYSSEY_E JPS EGGDT #AR_L12Y30N3030 YAR3 YARR 0.020 94 0.9 4 0.9 95.7 G 0.034 0.007 LEICA GRX1200GGPRO LEICA GRX1200PRO #AR_L12YAY33030 YAR2 YAR3 0.018 90 0.9 4 0.9 95.6 G 0.039 0.006 ASHTECH UZ-12 LEICA GRX1200GGPRO #AR_L12---------------------------------------------------------------------------------------------------------------------Tot: 30 1.211 3388 4.0 58 4.5 98.3 G 0.347 0.033 #AR_L12Tot: 9 0.275 992 1.1 0 1.8 100.0 R 0.193 0.017 #AR_L12Tot: 30 1.211 4380 4.0 58 4.5 98.7 GR 0.347 0.030 #AR_L12


LS combination of CODE’s accumulated IGSFINAL and EPNFINAL SDByyssss.LST results (WL)

ASHTECH Z18 : 22.120 2.268

JAVAD TRE_G3TH DELTA: 218.901 0.675

JPS EGGDT : 58.271 0.606

JPS E_GGD : 128.505 0.565

JPS LEGACY : 111.921 0.609

LEICA GRX1200+GNSS : -269.900 0.753

LEICA GRX1200GGPRO : -242.546 0.484

NOV OEMV3 : -247.286 0.516

SEPT POLARX3ETR : -501.984 0.533

TPS EGGDT : 70.275 0.726

TPS EUROCARD : 155.776 0.652

TPS E_GGD : 121.529 0.868

TPS LEGACY : 92.682 0.517

TPS NETG3 : 52.682 0.507

TPS ODYSSEY_E : 57.586 0.611

TRIMBLE NETR5 : 96.551 0.515

TRIMBLE NETR8 : 74.919 0.908

Receiver type SD bias RMS error (ns)


LS combination of CODE’s accumulated IGSFINAL and EPNFINAL SDByyssss.LST results (NL)

ASHTECH Z18 : -53.101 0.430

JAVAD TRE_G3TH DELTA: 141.433 0.312

JPS EGGDT : 84.758 0.241

JPS E_GGD : 115.096 0.305

JPS LEGACY : 122.283 0.248

LEICA GRX1200+GNSS : -249.992 0.369

LEICA GRX1200GGPRO : -232.233 0.179

NOV OEMV3 : -240.388 0.160

SEPT POLARX3ETR : -451.307 0.270

TPS EGGDT : 93.924 0.323

TPS EUROCARD : 138.133 0.276

TPS E_GGD : 103.681 0.241

TPS LEGACY : 95.540 0.166

TPS NETG3 : 91.903 0.151

TPS ODYSSEY_E : 83.337 0.250

TRIMBLE NETR5 : 80.976 0.161

TRIMBLE NETR8 : 75.959 0.279

Receiver type SD bias RMS error (ns)


� GNSS (mixed)

� GNSS (unmixed)

Implemented “GPS/GLONASS-Capable”LAMBDA Ambiguity Resolution Scheme(s)


Contents

• Introduction



Intersystem phase biases (1/4)

• Number of double-difference observations (per epoch) for four different analysis (or combination) scenarios, assuming 4 GPS and 2 GLONASS satellites in view.



• GPS-GLONASS inter-system phase bias variability, specifically the ionosphere-free linear combination of L1 and L2 biases, for baseline ZIMJ-ZIMT, for days 309–315, 2006 (GPS week 1400).



• GPS-GLONASS inter-system phase bias variability, the ionosphere-free linear combination (LC) of L1 and L2 biases, compared to biases directly associated with L1 and L2, for baseline ZIMJ-ZIMT, for day 309, 2006.



• Variability of epoch parameters compensating a supposed “GPS-GPS” differential phase bias between two sets of PRNs (PRN 01–16 and PRN 17–32), the ionosphere-free linear combination (LC) of L1 and L2 biases, compared to biases directly associated with L1 and L2, for baseline ZIMJ-ZIMT, for day 309, 2006.


Contents

• Introduction



GLONASS-GPS intersystem translation parameters with respect to station coordinates

GPS

North

East

Up

GPS

North

East

Up

GPS

GLONASS

North

East

Up

GPS

GLONASS

Mixed RP


GLONASS-GPS intersystem translation parameters with respect to troposphere ZPD

Time

Troposhere ZPD

GPS

Time

Troposhere ZPD

GPS

GLONASS

Time

Troposhere ZPD

GPS

GLONASS


GNSS analysis updates and treatment of these intersystem translation parameters at CODE

• Since GPS week 1619 (EUREF: 1615), an extra set of (3+1) parameters is set up for each GLONASS observing station to characterize- a GLONASS-GPS receiver antenna offset vector and- a GLONASS-GPS ZPD troposphere bias.

• Starting with GPS week 1625, these GLONASS-GPS bias parameters (4 for each GNSS station) are determined on a weekly basis and subsequently used for generation of our daily IGS analysis results.

• Note 1: The datum definition used for the GLONASS-GPS receiver antenna offset vectors is similar to that used for station coordinates: no-net translation and no-net rotation conditions with respect to all GLONASS observing stations are imposed.

• Note 2: GLONASS-GPS ZPD troposphere biases are generally treated unconstrained.

• Note 3: Our weekly SINEX contribution implicitly includes these GLONASS-GPS bias parameters (4 for each GNSS station).


Mean GLONASS-GPS troposphere ZPD biases: CODE EUREF (regional) weekly results

GLONASS-GPS troposphere ZPD biases (for up to 33 EUREF GNSS stations)

-0.5

0

0.5

1

1.5

2

1610 1615 1620 1625 1630 1635

Time (GPS week)

Tro

posp

here

ZP

D b

ias

(mm

)

Mean

Median

Model switch from IGS05 to IGS08


Mean GLONASS-GPS troposphere ZPD biases: CODE IGS (global) weekly results

GLONASS-GPS troposphere ZPD biases (for up to 143 IGS GNSS stations)

-0.5

0

0.5

1

1.5

2

1615 1620 1625 1630 1635 1640

Time (GPS week)

Tro

posp

here

ZP

D b

ias

(mm

)

Mean

Median

Model switch from IGS05 to IGS08


GLONASS-GPS translation parameter results concerning N/E and U/ZPD: EUREF week 1632

North versus East (EUREF week 1632)

-8

-6

-4

-2

0

2

4

6

-2 -1 0 1 2 3 4

East (mm)

Nor

th (

mm

)

Up versus ZPD (EUREF week 1632)

-10

-8

-6

-4

-2

0

2

4

6

8

-2 -1 0 1 2

ZPD (mm)

Up

(mm

)


GLONASS-GPS translation parameter results concerning N/E and U/ZPD: IGS week 1632

North versus East (IGS week 1632)

-10

-8

-6

-4

-2

0

2

4

6

8

-10 -5 0 5 10 15

East (mm)

Nor

th (

mm

)

Up versus ZPD (IGS week 1632)

-20

-15

-10

-5

0

5

10

15

20

-8 -6 -4 -2 0 2 4 6

ZPD (mm)

Up

(mm

)


GLONASS-GPS translation parameter results concerning N/E and U/ZPD: “GNSS-only” test analysis covering 3 years (2008–2010)

North versus East (GNSS 2008-2010)

-10

-8

-6

-4

-2

0

2

4

6

8

10

-10 -5 0 5 10

East (mm)

Nor

th (

mm

)

Up versus ZPD (GNSS 2008-2010)

-30

-20

-10

0

10

20

30

40

50

-15 -10 -5 0 5 10

ZPD (mm)

Up

(mm

)


GLONASS-GPS translation parameter results (reprocessed) (1/2)

Comparison of mean GLONASS-GPS biases (2003-2010)as computed for station height and troposphere IGS05:

IGS08:


GLONASS-GPS translation parameter results (reprocessed) (2/2)

Comparison of mean GLONASS-GPS biases (2003-2010)as computed for station height and troposphere IGS05:

IGS08:


Summary and conclusions

• Consideration of intersystem translation parameters specific to each GPS/GLONASS (as introduced by CODE) is a further step towards consistent multi-GNSS analysis.

• These GLONASS-GPS bias parameters (4 for each GNSS station) are kept in our NEQ results (for later manipulation).

• To consider station coordinates with respect to each GNSS is equivalent. Consequently, datum definition of ISTPs is essential.

• Intersystem receiver antenna calibration (concerning LC). • ISTPs are “multi-GNSS monitoring parameters” relevant to the

realization of ITRF (when relying on multiple GNSS).- Example: Mean GLONASS-GPS troposphere ZPD bias

vanishes after the switch to the IGS08 GNSS PCV model. • A set of ISTPs is desired with respect to each observed GNSS …


North

East

Up

GPS

GLONASS

More and more GNSS …

North

East

Up

GPS

GLONASS

Third GNSSNorth

East

Up

GPS

GLONASS

Third GNSS

Fourth GNSS


Contents

• Introduction



IGS ANTEX model (igs08.atx) (1/4)








Addition in terms of GNSS antenna phase center modeling• GNSS satellite antenna phase center offsets and variations

are commonly referred to the ionosphere-free LC• A set of corresponding parameters is set up in CODE’s

ionosphere analysis (with respect to the geometry-free LC)- retrieval of GNSS antenna information for L1 and L2


Our basic principle

• Multi-GNSS analysis with best possible consistency (among all considered GNSS) is strived for:- all significant biases must be taken into account (either

modeled/corrected or estimated)- finding the optimum/tradeoff between over and under

estimation of an analysis problem

Documents

Overview of GNSS biases - Portal · Overview of GNSS biases Stefan Schaer Swiss Federal Office of Topography (swisstopo) / CODE@AIUB ... (TGD) as broadcast by the GPS • Parameters