Post on 02-Aug-2020
ENC‐GNSS 2011, London, 1 December 2011 1
Use of EGNOS in road environments:
the SCUTUM multipath mitigation algorithm
A. Di Fazio, D. Bettinelli, G. Plaia
K. O'Keefe, G. Lachapelle
ENC‐GNSS 2011, London, 1 December 2011 2
Contents
Objective of the study
EGNOS/EDAS
SCUTUM
The project
Architecture
Multipath mitigation algorithm concepts
Validation methodology
Results
Conclusions and steps forward
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Objective of the study (1/2)
Enhancing the Telespazio LCS EGNOS navigation solutionby means a multipath mitigation algorithm
Telespazio patented solution that makes use of EGNOS CS distributed via EDAS to augment EGNOS OS performance
The multipath mitigation algorithmDesigned in cooperation with the University of Calgary to mitigate the effects of code multipath on the LCS
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Objective of the study (2/2)
Trial campaign to:
– Assess LCS performances
– Validate the effect of the multipath mitigation algorithm on the LCS in rural, suburban and urban environments
– Tune the implemented multipath mitigation algorithm
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EGNOS/EDAS
operational
operational
under beta test
EGNOS services for land and mobility applications:
EGNOS OS (from SiS)
EGNOS CS (from EDAS ‐ EGNOS Data Access Service)– controlled access, distributed by EDAS via terrestrial networks
– enabling to augment the performances of the EGNOS OS through EGNOS CS/EDAS based solutions (e.g. the LCS)
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SCUTUM project
EU GSA R&D project
Use of GPS/EGNOS for the tracking & tracing of dangerous goods by road
GPS+ EGNOS OS + EGNOS CS/EDAS
Operational adoption (300 operational tankers in EU * monitored with GPS/EGNOS)
* Italy, France, Austria, Slovakia, Hungary, Romania, Czech Republic
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SCUTUM Architecture
Value‐AddedService Provider
EGNOS msg
Positions and raw data
Corrected position and Protection level
CEN Workshop Agreement SCUTUM
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LCS functions
LCS runs on the tracking & tracing platform
Gets EGNOS data from EDAS/ process
Returns EGNOS CS/EDAS based services *:
– EGNOS corrections, always or only in case of difficult environment
– Protection level→ exploitation of the integrity
* MOPS RTCA/DO‐229D suitably customized for road environments
→ enhanced accuracy and availability of EGNOS augmentation
→ confidence on the position→ qualification of raw data from the receiver/ position guarantee
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Multipath mitigation algorithm concepts (1/3)
The FDE procedure consists of some sequential steps and iterations
The procedure ends once no further outliers are isolated or the number of remaining observations is less or equal to five or several special case conditions occur
By means of statistical methods, the algorithm detects multipatheffects, which are considered in the LCS processing
Combined statistical‐empirical method:
–A “fault detection and exclusion” (FED) procedure using a statistical reliability method for the detection and removal of pseudorangeobservations corrupted by multipath
–A procedure for “field testing” using the receiver under study and a geodetic quality receiver to provide a reference estimate of code multipath
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Multipath mitigation algorithm concepts (2/3)Parameters of the multipath mitigation algorithm
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Multipath mitigation algorithm concepts (3/3)
–A higher elevation mask or a higher C/N0 corresponds to a highernumber of rejected measurements
–The rejection threshold rejects outliers if the relevant standardized residual exceeds the specified threshold. A higher value for thethreshold corresponds to a lower number of rejected outliers
–DRMS is proportional to the satellite geometry and the estimatedobservation variances. The check on the DRMS is done on the computation of the navigation solution. A higher value for DRMS corresponds to a lower number of rejected computations
–HPL is computed by the navigation solution. The check on the HPL is done on the computation of the navigation solution. A higher value for the specified HPL corresponds to a lower number of rejected computations
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Validation methodology (1/3)
–True path/ reference trajectory calculated in post‐processing, through a kinematic differential GPS method, by using GPS L1 and L2 carrier phase measurements, combined with INS
–Two OBUs and the GPS/INS system installed in a test vehicle and connected to a common external GPS antenna
–Two antennas: a Novatel and a standard patch
–Three LCS’s configuration
“LCS baseline”
“LCS enhanced” with default parameters
“LCS enhanced” with tuned parameters
–Comparison of HNSE and HPL
run in post processing
run in real/time
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Validation methodology (2/3)
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Validation methodology (3/3)Five driving environments
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Results ‐median HNSE
Novatel antenna standard antenna
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Results ‐ 95th percentile HNSE
Novatel antenna standard antenna
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Conclusions and steps forward
–For the SCUTUM application and uses, the “LCS baseline”implementing the baseline multipath mitigation method (based on the proprietary patented algorithm) is the most performing one
–“LCS baseline” key performances comparison wrt GPS/GPS+EGNOS OS
–Results are due to a pessimistic parameters’ tuning requiring further tuning to enhance the effectiveness of the multipath mitigation
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Thank you for your attention.Questions?
Contacts:www.scutumgnss.euAntonella Di Fazioantonella.difazio@telespazio.com