The French Institute of Science and Technology for Transport ... · positioning on Android devices...
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Enabling high precision positioning on Android devices The French Institute of Science and Technology for Transport, Development and Networks Antoine GRENIER Céline RAGOIN Valérie RENAUDIN GNSS measurements Taskforce Workshop Prague, June 26th 2019 1
Transcript of The French Institute of Science and Technology for Transport ... · positioning on Android devices...
Enabling high precision positioning on Android devices
The French Institute of Science and Technology for Transport,
Development and Networks
Antoine GRENIERCéline RAGOINValérie RENAUDIN
GNSS measurements Taskforce WorkshopPrague, June 26th 2019
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www.ifsttar.fr26/06/2019
Road to PPP-RTK
● Raw measurements○ Validity & quality
● Modelling○ Precise orbits & clocks for satellites○ Tropospheric corrections○ …
● Signal combination○ Allow ionospheric correction (“Iono-free” combination)○ Require multiple frequency acquisition
■ Xiaomi Mi8 with L1 and L5 capacities
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www.ifsttar.fr26/06/2019 3Credits @ Roberto Lee Cortes
Environment c
onstraints
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Environment constraints
● Only 12 GPS satellites with L5 signals○ 4-5 available in open sky ○ Less in an urban canyon -> PPP system unsolvable or non redundant○ Use multiple constellations (GALILEO, BEIDOU, ...)
● Problem○ GALILEO navigation message not available on Xiaomi Mi8
● Solutions:○ SUPL Google○ IGS products (FTP)○ RTCM streams (RTS IGS)
● Radio Technical Comission for Maritime Services (RTCM) Protocol● Stream divided in messages (Observation, Navigation, Corrections...)
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Precise orbits& clocks
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Precise orbits and clocks
● Need precise products in real time○ IGS ultra-rapid products (predicted) using FTP○ RTCM streams from Real Time Service IGS
■ Need identifcation to access, freely available for research purposes
● Streams VS ultra-rapids products○ More accurate satellites clocks estimation [1]○ Available for all constellations○ Easy to implements
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[1] Tomasz Hadas and Jaroslaw Bosy. “IGS RTS precise orbits and clocks verifcation and quality degradation over time” (2014).
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Implementation in Android
● GoGPS Java open-source library ○ Java port of the Matlab code written by Mirko Reguzzoni and Eugenio
Realini (Geomatics Laboratory of Politecnico di Milano, Italy).
● Java toolbox ○ DGNSS-RTK computations, RINEX logging, …○ RTCM streams receiving and decoding capacities
● Problem○ Only observation messages (1004, 1006, …) decoded○ Classes for other messages need to be added
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Implementation in GeolocPVT
● GoGPS added in the source code of the app○ Enhanced for ephemeris/corrections messages
■ GPS (1019/1060)■ GALILEO (1045/1243)
○ Standard binary string decoding, specs in RTCM standards 10403.3 [2]
○ An working example can be found in RTKLIB open source code (C++)
● Log into the IGS-RTS server (www.rt.igs.org) ○ “RTCM3EPH” Mountpoint for ephemeris
■ Message 1019, 1045
○ “CLK93” Mountpoint for orbit/clock corrections■ Message 1060, 1243
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[2] RTCM. RTCM 10403.3, Differential GNSS (Global Navigation Satellite Systems) Services. Radio Technical Commission For Maritime Services. 2016.
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Results
Future developments of GeolocPVT○ Management of internet data resources○ Toward an effcient PPP-RTK solution○ ...
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References
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[1] Tomasz Hadas and Jaroslaw Bosy. “IGS RTS precise orbits and clocks verifcation and quality degradation over time”. In: (2014).[2] RTCM. RTCM 10403.3, Differential GNSS (Global Navigation Satellite Systems) Services. Radio Technical Commission For Maritime Services. 2016.
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Raw measurements
● Validity○ Pseudorange and phase need to be independent from each other
■ Ex: Low cost receivers
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Source: Zhu Ni, GEOLOC/IFSTTAR
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Raw measurements
● Validity - Xiaomi Mi8 results
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Raw measurements
● Quality○ Precise phase measurements○ Fewest cycle slip possible
■ Ambiguity estimation and resolution
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Applying corrections
● Applied on coordinates computed from broadcast ephemeris
● Broadcast ephemeris can be retrieved from streams
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○ IoD (Issue of Data) id of broadcast and corrections need to be similar
Source: Schmitz, 2012 [2]For details see references [2, 3]
[2] Martin Schmitz. RTCM State Space Representation Messages, Status and Plans. Geo++ GmbH, 2012.[3] RTCM. RTCM 10403.3, Differential GNSS (Global Navigation Satellite Systems) Services. Radio Technical Commission For Maritime Services. 2016.
