“Receiver type depending part of observed satellite wide lane delays (GPS L1/L2 only).” S. Loyer, CNES/CLS AC Team (grg/grm products)

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Known interests of IPPP : - Allows single-receiver ambiguity fixing (simplifies the user-side) - Improves solutions vs float-PPP (mainly in East direction) - Continuous (over months) GPS phase clocks improve receiver clocks estimates (Petit et al. 2015)

Widelane Satellite Biases & IPPP user level

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• IPPP = Integer ambiguity PPP with GINS and GRG SV products and WL biases

• PPP = NRCan continuous solution with IGS SV products

• IPPP had 100% success at solving integer lc boundaries over ~6 months

• A 41-day period (longest continuous operation for all systems):

– Stability of IPPP better at few hours and at long term : 5.3x10-17 @ 7.1 days

– PPP apparent slope of order 1x10-16 , IPPP has no significant slope

IPPP and PPP vs. 420-km optical fiber link (1/2)

Blue = IPPP – Fiber link

Red = NRCan – Fiber link

1 NL ambiguity

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• Another 22-day period:

– PPP has apparent slope of order several 10-16 , IPPP has no significant slope

– Stability of IPPP better at few hours and at long term : 1.1x10-16 @ 3.6 days

IPPP and PPP vs. 420-km optical fiber link (2/2)

Blue = IPPP – Fiber link

Red = NRCan – Fiber link 1 NL ambiguity

See Metrologia paper

-> Wide Lane satellite Biases (WSB) are computed after applying P1-C1 biases (p1c1bias.2000p) if needed. -> WSB are slowly varying in time. Receiver part bWLrec fairly stable for some receivers.

-> This form suppose that WSB are independent of the receivers or can be derived from any set of receivers. But …

I. How big are the deviations from this model ?

II. What is the dependence on receiver types ?

III. Impact on WL fixing methods ? Needs to take this into account ?

noiseWLrecWL tWSBtbNMW )()(

CNES/CLS IGS-AC use the Melbourne Wübbena Wide Lane at the undifferenced level with the following model expressed in WL cycles:

[1] Laurichesse D., Mercier F., Berthias J.P., Broca P., Cerri L. Integer Ambiguity Resolution on Undifferenced GPS Phase Measurements and Its Application to PPP and Satellite Precise Orbit Determination. Navigation, Journal of the Institute Of Navigation, pp 135-149, Vol. 56 N° 2, 2009 [2] Loyer S., Perosanz F., Mercier F., Capdeville H., Marty J.C. Zero-difference GPS ambiguity resolution at CNES–CLS IGS Analysis Center. Journal of Geodesy. Springer Berlin / Heidelberg. Doi: 10.1007/s00190-012-0559-2, 2012.

Widelane Satellite Biases : used formulation/definition, cf. [1][2].

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[1] The Effect of Correlator and Front-End Design on GNSS Pseudorange Biases for Geodetic Receivers, André Hauschild & Oliver Montenbruck, ION, Sept. 14-18, 2015, Tampa, Florida.

I. How Big ? : A recent study[1]

Zero Baseline experiment for various modern receivers. order of magnitude : some 0.1 WL cycles (max 0.25 cycles )

depends on receiver type

depends on correlator settings

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I. How Big ? : Two independent realizations of GPS WSB

Solution 1 : Real-Time solution from PPP-wizard project network : ~ 50 stations from IGS network : wl bias reconstructed from individual p1/p2/l1/l2 series[1] .

Solution 2 : Final GRG/IGS-AC set: daily mean of ~130 receivers from IGS network. Different networks, different methods, different software, same MW equation. Comparison of the two realizations at noon for ~ 40 recent days (after correction of +/- n

arbitrary integers) :

1 curve =1 GPS satellite

} +/- 0.1 WL cycle

Stable differences . Due to network differences ?

[1] D. Laurichesse, Apr. 2015, gpsworld.com/innovation-carrier-phase-ambiguity-resolution => )/1/()/(/1 21221121 lllll ppwlLL bbbbWSB 7

Data used : • 137 days used • 170 receivers (including all MGEX/RINEX3 available at that time + some “old” RINEX2 from IGS data centers) • Keeping only sites with no equipment changes Method : 1. Apply C1C-> C1P & C2C -> C2P DCB if needed. 2. Compute WL biases on a daily basis for each receivers => give one individual set of WSB per receiver (~137 days time span) => mean values of all receivers give the reference set 3. Also: compare two by two all sets and reduce it to a global RMS for each

couple of receivers.

Family Nb receivers

Aschtech & Tps 33

Javad 29

Jps 4

Leica 26

Septemtrio 14

Trimble (1) 20

Trimble (2) 44

Aoa 1

Nov OEMV3 1

Single-receiver WSB series : Since end of 2014 we follow the individual receivers WSB values of a subset of the IGS network (1 point per day and satellite)

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How Big ? : Two examples of visible effects of equipment change

9 Note: LEICA GRX1200GPRO & TRIMBLE NETR5 are Non-cross-correlator receivers (reporting C1 instead of P1)

Up to 0.25 WL cycles in some cases !

How Big ? : Two examples of visible effects of equipment change

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How big : Two examples if single-receiver WSB sets: One good and one bad agreement with reference set (mean).

1 curve =1 GPS satellite

1 curve =1 GPS satellite

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II. All receivers comparisons together 1 point per couple (rms) sorted by receiver type :

* Receiver type dependence clearly visible * Few receivers do not fit with their “family “ * There are two families for Trimble receivers !!

=> possible to define a set per family

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Max = 0.13 WL cycles RMS

Nearly all are NETR9 (with mainly TR59800.00 antenna). Any association with either : antenna,radome [*] / receiver#,type,version[*] / converter[*] …. shows no clear correlation !

[*] taken from RINEX headers

The best correlation found is … with the operating agency !? (different settings ? )

The two “families” for trimble ? Causes ?

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Inadequate WSB values could give erroneous WL fixing. This mainly depends on the robustness of the algorithms used ! Test of an extreme case with our software for undifferenced WL fixing : use of trimble 1-WSB or trimble 2-WSB (~ 0.12 cycle RMS) on a “trimble2” receiver (10

days of BRST receiver data) => Ambiguity solutions are identical in the two cases except for 4 very short passes

eliminated in the first case

What impact on WL fixing when using inadequate values ?

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From Wide-Lane ambiguity fixing anomalies observed in Repro2 solutions, F. Mercier, F. Perosanz, S. Loyer, H. Capdeville, IGS Workshop 2014

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Use of receiver type families biases (here C1P1) can facilitate the Wide-Lane fixing.

-> GPS L1L2 WSB are routinely observed from a global network of receivers -> Useful for IPPP

-> Single receiver type determination of WSB is also possible:

- general good agreement

- characteristics of Trimble receivers of the IGS network not understood

- up to ¼ WL cycles differences are observed

- can be managed by robust algorithms

- useful to check the compatibly of new/unknowns receivers (with mean values)

-> Future :

- maintain receivers families biases ?

- WSB for others systems (Galileo/Beidou/etc..) & frequencies (L1L5)

Thank you for your attention.

Concluding remarks

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