Towards Autonomous Driving on road: the E-GNSS contribution

From basic concepts to "local integrity"

Speakers: Ing. Gianluca Marucco Mr. Matteo Vannucchi Moderator: Ing. Gabriella Povero

Table of Content

3

Introduction

GNSS Principles

European GNSS

Integrity

Table of Content

4

Introduction

GNSS Principles

European GNSS

Integrity

Autonomous Driving

Technologies relevant in driver assistance systems and autonomous vehicles:

• vehicle electronics

• vehicle dynamics

• command/control

• HMI

• perception

• computer vision

• data-fusion

• communication

• eco-driving

• … and NAVIGATION!

5

2009 by Kozuch

By ESA/RAL Space/ESO - http://www.eso.org/public/images/ann12048a/, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=19979586

Autonomous Driving

Role of GNSS:

• routing can be decided using digital maps.

• navigation by determining vehicle location and speed

• lane and attitude determination

• short-range situation awareness system (awareness of other vehicles in the road and collision avoidance) in combination with positional information sharing among cars

6

Table of Content

7

Introduction

GNSS Principles : introduction

European GNSS

Integrity

Global Navigation Satellite Systems

8

GNSS enable users (on Earth surface or flying) to determine their position with respect to a Reference Frame

x

y

z

Trilateration

9

The receiver is able to measure the TOA (Time Of Arrival) and consequentially the distances

Transmitters are in known positions

The receiver is in an unknown position

10

The Basic Tool: the Clock

The Time Of Arrival is measured by the receiver The time of departure is known (set by transmitter)

The travel time is their difference The distance is the travel time multiplied by the

speed of light.

Transmitters and receivers MUST be equipped with clocks.

11

The Basic Tool: the Clock

Time difference between TX and RX is the basis.

TX and RX clocks must be synchronized

Synchronization error of 1μs corresponds to an error distance of approx. 300 m

Very onerous requirement!!

12

Trilateration by Satellites

),,( ooo zyx

x

y

z

),,( kkk zyx

The user to be located (receiver) Unknown position

The satellites are equipped with atomic clocks

Satellites are at known positions, as we know the orbits and the satellite time

Transmitters are on board satellites

13

GNSS in One Slide

A Global Navigation Satellite System (GNSS) consists of a constellation of satellites

with global coverage, whose payloads are designed to provide positioning of objects

x

y

z

GNSSs implement the trilateration method

(spherical positioning systems)

The satellites are at known positions, as we know satellite orbits and time

Reference Coordinate Systems and Frames Time Scales

14

3D Positioning

EARTH

Three distance measurements appear to be enough for positioning in a three dimensional space

15

How Many Satellites?

Why?

To sidestep the synchronisation requirement

),,( ooo zyx

x

y

z

),,( kkk zyx 4 Satellites

16

Ranges and Pseudoranges

),,( ooo zyx

x

y

z

),,( kkk zyx

TOA measurements at the receiver are affected by the same clock bias )( cb

)( cb )( rb

Receivers are equipped with inexpensive quartz oscillators.

The range bias becomes the fourth unknown to be estimated

)( rb

Because of the bias pseudoranges are measured instead of ranges

)( rb

The Navigation Equation

17

• In order to estimate its position a receiver must have at least four satellites in view

• The satellites must be in Line-of-Sight

• If a larger number of satellites is in view a better estimation is possible. In the past the combination of four satellites giving the best performance was chosen

• Modern receivers use several channels in order to perform the position estimation

REMARKS

x

y

z

Table of Content

18

Introduction

GNSS Principles: receivers

European GNSS

Integrity

19

Control system errors: • Clocks • Ephemeris

The Hard Work of GNSS Receivers

Multipath

Interference and jamming

Indoor

Bluetooth

WLAN

Urban canyons

Atmospheric errors: • Ionosphere • Troposphere

Doppler ↔

Low SNR

20

SE-NAV simulation: Multipaths in a station

21

The Receiver Chain

Let us consider the SIS of a single SV (space vehicle)

SIS (Signal in Space)

Antenna RF

Front-end ADC

GNSS

Digital

receiver

)(tyIF

)(tyRF

Pseudorange

GNSS Receiver Operations

22

Acquisition

Sky search

Tracking

Measurements

Refines code and carrier alignment

Search for IDs of visible satellites

Code delay and Doppler estimates, rough alignment of code and carrier

Pseudorange and data demodulation

1

2

3

4

Computation Usually the PVT

Integration with external info

Not present in all receivers

HMI Not present in all receivers

5

6

7

GNSS Receiver Operations

23

Receiver Performance

24

Receivers Classes

Receivers Specifications

Description Device Price [€]

Handheld receivers for hikers and sailors. Small size with latitude-longitude displays and maps. 100 - 600

Integrated GPS in mobile phones. Low cost and single frequency. 50-600

Maritime navigators. Fixed mount, large screens with electronics chart 100-3000

In-car navigation systems. Detailed street maps and turn-by-turn directions. These systems can be also handheld (e.g. PDA)

100-2000

Receivers Classes

25

Price differences are due to reason independent from the embedded GNSS chip

Description Approx. Price [€]

Aviation receivers. FAA in US and EASA in Europe certified, panel mounted with maps.

INTEGRITY REQUIRED !

>3000

Survey and mapping professional receivers. Multi-frequency and differential GPS, centimeter accuracy

1500 – 30000

Receivers Classes

26

Price differences are due to reason independent from the embedded GNSS chip

Description Approx. Price [€]

Plug-in modules. Integrated receivers and antenna. Employed in tracking systems

30 – 700

OEM boards. Employed for integration in other complex systems.

100 – 5000

Chip sets. Employed for integration, but all the circuitry is needed

1 – 30

GNSS Modules

27

Professional vs Mass-Market Receivers

28

Raw measurements availability

and configurability

Carrier Phase vs

Code Phase?

Configurability DGNSS … RTK

Receivers Classification: Market Segment

29

Category Receiver Characteristics

Consumer Single frequency, cost driven, high volume, moderate performance, also multi constellation

Light Professional

Single frequency, multi constellation, cost driven, low volume, good performance, integration with external devices, professional features

Professional Multi frequency, multi constellation, cost/requirements driven, low volume, high performance, advanced processing algorithms

Safety of Life Double/ Multi frequency, multi constellation, requirements driven, low volume, high performance, high reliability, integrity, certification

P R S Double frequency, low volume, high performance, high reliability, requirements driven, integrity, advanced processing algorithms

GNSS RX Features

30

• Constellation exploited

• Military or civil receiver

• PVT update rate

• Indoor operations or high multipath environment

• Interference mitigation

• Dynamic conditions (static or high dynamic)

• DGPS or WAAS/EGNOS capability (RTK input/ output)

• Storage of log data

• Shock and vibration tolerance

• Cartographic support

• INS integration or dead-reckoning systems

• Integration with COM systems

• Portability

• Usability

• Power consumption

• Cost

Example of Technical Specification (1)

31

Septentrio PolaRx4 PRO

• 264 hardware channels

• TRACK+: Septentrio’s low-noise tracking algorithms,

• GPS L1/L2/L2C/L5,

• GLONASS L1/L2

• Galileo E1, E5a, E5b, E5 AltBOC and

• GLONASS CDMA L3

• experimental tracking of Beidou signals

• AIM+: Advanced Interference Monitoring and Mitigation

• APME+: extends Septentrio’s patented A Posteriori Multipath Estimator to GLONASS, Galileo and Beidou signals

• ATrack+: is Septentrio’s patented Galileo AltBOC tracking.

Example of Technical Specification (2)

32

Septentrio PolaRx4 PRO

Pseudorange noise (not smoothed) Carrier Phase

GPS L1 C/A 16 cm L1/E1 <1 mm

GLONASS L1 open 25 cm L2 1 mm

Galileo E1 B/C 8 cm L5/E5 1.3 mm

Galileo E5 A/B 6 cm Doppler

Galileo E5 AltBOC 1.5 cm L1/L2/L5 0.1 Hz

GPS L2 P(Y) 10cm

GLONASS L2 (mil) 10m

Example of Technical Specification (3)

33

NovAtel 628

• 120 hardware channels

• GPS L1 L2 L2C L5

• GLONASS L1 L2

• Galileo E5a E5b E5 AltBOC

• Beidou B1 B2

• QZSS

• L-Band

• RT-2 (RTK algorithm)

• Pulse Aperture Correlator (PAC) multipath mitigation technology

• SPAN INS integration technology

• …

Example of Technical Specification (4)

34

NovAtel 628

Pseudorange noise (not smoothed) Carrier Phase

GPS L1 C/A 4 cm L1 GPS 0.5 mm

GLONASS L1 open 8 cm L1 GLONASS 1 mm

GPS L2 P(Y) 8 cm L2 1 mm

GPS L2C 8 cm L2C 0.5 mm

GPS L5 3 cm L5 0.5 mm

GLONASS L2 open 8cm

GLONASS L2 mil 8 cm

Example of Technical Specification (5)

35

NovAtel 628 Position Accuracy (RMS) Signal Reacquisition

Single point L1 1.5 m L1 <0.5 s (typical)

Single point L1/L2 1.2 m L2 <1.0 s (typical)

SBAS (GPS) 0.6 m Maximum Data Rate

DGPS 0.4 m Measurements 100 Hz (20 SV)

L-band VBS 0.6 m Positions 100 Hz (20 SV)

L-band XS 15 cm Vibration

L-band HP 10 cm Random vibe MIL-STD 810G

(Cat 24, 7.7 g RMS)

RT-2 1 cm + 1ppm (BL) Sine vibe IEC 60068-2-6

GNSS Receivers Capability

36

GNSS Market Report 2015 - GSA

37

-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2-2.5

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

East Error(m)

Nort

h E

rror(

m)

The position error w.r.t the mean position of GPS & GALILEO

GPS

GALILEO

Galileo Real Early Performance (2014)

• Galileo is benchmarked to GPS in terms of precision in the estimation of the position

• In mid 2014 only 3 Galileo satellites were transmitting a valid navigation message

• The position computation was performed using L1 data from:

o 5 GPS satellites

o 3 Galileo + 2 GPS satellites

• Chosen GPS and Galileo satellites were those in view during the same time period and which elevation and azimuth angles were similar in pairs. The aim of this scenario is to have common ionospheric and troposheric effects for both the systems

Table of Content

38

Introduction

GNSS Principles

European GNSS: EGNOS - EDAS

Integrity

Augmentation: Purposes

39

An augmentation system has the general objective of improving the use of GNSS, through

the provision of additional information.

Some categorization can be done:

• Systems that keep the focus on the accuracy. They are intended for:

o LBS in general including leisure

o Mapping

o Cadastral

o Surveying

• Systems for Safety of Life applications:

o Air navigation

o Water navigation

o Transportations in general

• Systems for other services with

legal or liability implications:

o Road Tolling

o EEZ

EGNOS

40

• EGNOS is the EUROPEAN AUGMENTATION system

• Its purpose is to enable aircrafts to use GPS for all phases of flight, from en route down to precision approaches to any airport within its coverage area.

• EGNOS was promoted by European Tripartite Group formed by Eurocontol, the European Community and the European Space Agency.

• Its main features are the provision of:

o Wide Area Differential corrections

o Integrity information

Currently it improves the use of GPS

41

EGNOS Services

EGNOS provides three services: • Safety of Life

– http://egnos-user-support.essp-sas.eu/new_egnos_ops/sites/default/files/library/official_docs/egnos_sol_sdd_in_force.pdf

• Open Service

– http://egnos-user-support.essp-sas.eu/new_egnos_ops/sites/default/files/library/official_docs/egnos_os_sdd_v2_2.pdf

• EDAS (EGNOS Data Access Service)

– http://egnos-user-support.essp-sas.eu/new_egnos_ops/sites/default/files/library/official_docs/egnos_edas_sdd_v2_1.pdf

EGNOS Reception Problems

42

Brand Model EGNOS in use Tracking SV 120 Tracking SV 126

µblox LEA 6-T 40.3% 20.1% 30.8%

NovAtel FlexG2-V2 35.5% 12.7% 16.1%

GPS without correction

GPS corrected by EGNOS

EGNOS Data Access Service (EDAS)

• EGNOS is now providing a terrestrial commercial data service: EDAS

o EDAS offers ground-based access to EGNOS data.

o EDAS is the single point of access for the data collected and generated by the EGNOS infrastructure.

• The main types of data provided by EDAS are:

o GPS, GLONASS and EGNOS GEO data collected by the entire EGNOS stations network

o EGNOS augmentation messages identical to those broadcast via Geostationary Satellites

o Antenna phase centre coordinates for each EGNOS reference station.

43

EDAS Main Purposes

EDAS allows registered users to plug into EGNOS to receive the internal data collected, generated and delivered by EGNOS.

EDAS therefore provides an opportunity:

• to deliver EGNOS data to users who cannot always view the EGNOS satellites (such as in urban canyons)

• to support a variety of other services, applications and research programmes.

EDAS services are intended to be delivered and maintained over the long term.

44

EDAS Applications

• Redistribution of EGNOS augmentation messages:

– They can be exploited in urban canyons for user communities with their own equipment standards

• A-GNSS (Assisted GNSS) for Location Based Services: this application can be used by many user communities, such as:

– Mobile network operators to provide positioning assistance service to their customers

– Third parties in order to offer Location Based Services in urban areas.

– Emergency services using the position information of mobile phones.

– Network operators in order to use input data to support current or future A-GNSS services.

45

EDAS Applications

• Professional GNSS Services: for users within surveying, oil and gas exploration, mapping, construction, tracking and more.

• Development and validation of added value applications.

• Supporting geodetic and mapping research.

• Application of DGNSS and RTK positioning techniques in areas close to EGNOS stations in order to enhance precision

• EGNOS messages through SISNeT for mobile receivers with Internet access, irrespective of the GEO visibility conditions in order to improve accuracy with respect to GPS.

• Research initiatives linked to the analysis of the atmosphere behaviour.

• Offline and real-time processing for GNSS performance analysis.

46

EDAS Architecture

47

EDAS Services

The EDAS services are classified in:

• Main Data Stream Services deliver raw data via:

– Service Level 0 (SL0): it is needed to either transmit data in raw format, or transmit them in a format that allows a complete reconstruction after decoding.

– Service Level 2 (SL2): it is used to transmit data in RTCM 3.1 standard.

• Data Filtering service allows EDAS users to access a subset of the SL0 or SL2 data to reduce bandwidth consumption

• FTP service enables EDAS users to get EDAS/EGNOS historical data in different formats and data rates

• SISNeT service provides access to the EGNOS GEO satellites messages over the Internet through the SISNeT protocol (defined by ESA in 2002)

• Ntrip service provides data from the EGNOS network through the Ntrip protocol which represent the standard for differential correction distribution

48

Added Value for ITS

Improved accuracy and in particular integrity information provisioning play a key role for the implementation of some ITS applications like:

• E-Call: automatic emergency call and GNSS-based location

• Dangerous goods transport

• Advanced Driver Assistance Systems (ADAS)

49

Table of Content

50

Introduction

GNSS Principles

European GNSS: Galileo

Integrity

Galileo

51

• Initiative of the European Union (EU) and

the European Space Agency (ESA),

in collaboration with European Industries

• Galileo is a civil system under civil control

• Galileo offers more and new services

• Galileo is independent from GPS

• Galileo is compatible and interoperable with GPS

Galileo Adds-on

52

• Improved by new modulation schemes Precision

• Improved by specific orbit design * Availability

• Improved by specific orbit design * Coverage

• Improved by Authentication service (CS◊) Reliability

• Improved by High Accuracy service (CS◊) Accuracy

* advantage also by multi constellation ◊ Commercial Service

Galileo System Testbed v1 Validation of critical algorithms

GIOVE A/B 2 test satellites

In-Orbit Validation 4 fully operational satellites

and ground segment

Initial Operational Capability Early services for OS, SAR,

PRS

2003

2005/2008

2013

2015/2016

Full Operational Capability Full services, 30 satellites

2020

Galileo Implementation Plan

53

Definition of GNSS Signal Authentication

Authentication is the certification that a received signal is not counterfeit, that it originates from a GNSS satellite and not from a spoofer

Source: Wesson K., Rothlisberger M., Humphreys T., “Practical Cryptographic Civil GPS Signal Authentication,” Navigation, Journal of The Institute of Navigation, Vol. 59, No. 3, Fall 2012, pp. 177-193.

The presence of a cryptographically secure portion in the received GNSS signal is required: it is sometimes referred as:

security code

or

digital signature

54

Why Authentication?

• Demand of high quality Location-Based Services, able to provide high accuracy and reliable position and time information

• GNSS is used for liability-critical applications and commercially-sensitive Location Based Services: information about the user’s position or velocity is the basis for legal decisions or economic transactions

– E.g. Road User Charging, Pay-As-You-Drive insurances, mobile payments, etc.

• Surveillance and safety-critical systems rely on GNSS (e.g. dangerous goods transportation and law enforcement)

• There is a risk of intentional alteration of the GNSS signals by means of jamming, meaconing or spoofing attacks, made for frauds, illicit exploitation or offence purposes by hackers and terrorists

• Countermeasures can be possibly based on cryptographically secure signals Non-cryptographic defences are also possible

55

Spoofing Attack Detection with Authenticated Signal

56

57

Galileo Services

Open Service (OS) Freely accessible service for

positioning, navigation and timing

Public Regulated Service (PRS) Encrypted service designed for greater

robustness and higher availability

Search and Rescue Service (SAR) Assists locating people in distress and

confirms that help is on the way

Commercial Service (CS) Delivers authentication and high accuracy

services for commercial applications

Integrity Monitoring Service Provides vital integrity information

for life-critical applications

The former "Safety-of-Life" service is being re-profiled:

Authentication Provisioning

• The main services foreseen to be part of the CS are high accuracy and authentication

• Authentication scheme foreseen for CS can be based on both Spreading Code Encryption (SCE) and Navigation Message Authentication (NMA)

• Relying on these schemes the provision of two levels of authentication would be possible: – a data-based authentication service in the E1 I/NAV open signals for mass market users

– a data-based plus spreading-code based authentication service through the CS signals

58

Authentication Target Applications in the Road Domain

• Road User Charging (RUC)

• Digital Tachograph (DT)

• Logistics:freight transportation and fleet management

• Pay As You Drive (PAYD) also known as Pay-Per-Use Insurance (PPUI)

59

Summary

Integrity + Authentication = Reliability • The term reliability is used to refer to integrity and authentication together,

it means the availability of a trusted Position Velocity and Time (PVT) that can be exploited in liability-critical (as Road User Charging) and safety-critical applications (as Advanced Driver Assistance Systems)

• Now, it is worth to recall some specification about the level of maturity of the two features above:

– Authentication protects against false signal that can be generated intentionally: an authentication service once implemented offers a guarantee that still depends on the level of the attack

– Integrity has been validated for some applications (typically aviation) and research in other application fields is still undergoing in particular to take into account local effects (i.e. error sources) that can’t be easily modelled being related to local electromagnetic propagation effects (mainly multipath)

62

Table of Content

63

Introduction

GNSS Principles

European GNSS

Integrity

Integrity: Definitions

• Formal: ability of the system to provide timely warnings to users when it may not be used to navigate

• Informal: “I know I’m getting this accuracy, the system is not lying to me…” by dr. Brad Parkinson (GPS father)

64

Outline

65

• Need for GNSS integrity in road applications

• The novel “Local Integrity” approach

– Reference system architecture for the Local Integrity

– Cooperative estimation of the local GNSS degradations

• Experimental proof-of-concept

– Urban tests

• Prototype demonstrator of Local Integrity

Classic (Aviation-Born) Integrity Approach

• Principally defined in the aviation context

– For strictly Safety-of-Life applications

– Integrity information (Protection Levels)

provided by augmentation systems (SBAS or LAAS)

• Growing interest in other transportation fields

– Maritime, rail, and vehicular transportation fields

– Need for “reliable” (integer and possibly certified)

positioning information, especially in case of safety-critical or liability-

critical applications

• Applicability of “classic” integrity concepts is far from being straightforward

in case of non-aviation operations

– Deep reconsideration needed, especially in urban contexts

66

Does the Classic Integrity framework fit for the road domain?

67

It is possible to adopt the classic integrity mechanisms, for road applications?

1) Integrity and continuity risks too conservative

– At least for non-Safety-of-Life applications

2) Integrity and continuity risks assigned per phase of flight

– No matching with on-the-road behaviours

3) Aeronautical GNSS signal propagation models inconsistent

– They assume open-sky satellite visibility

– They assume diffuse ground multipath only, line-of-sight only propagation

– They often assume the availability of local differential corrections

No, it is not

Effect of the receiver and of the «local» environment nearby the receiver

Outline

68

• Need for GNSS integrity in road applications

• The novel “Local Integrity” approach

– Reference system architecture for the Local Integrity

– Cooperative estimation of the local GNSS degradations

• Experimental proof-of-concept

– Urban tests

• Prototype demonstrator of Local Integrity

The Novel “Local Integrity” Approach

69

• Methodology to quantify in average the effects of the local environment nearby the receiver

– Specifically designed for a road domain

– Intended to overcome the difficulty in modelling the local environment

• Proposed and developed in the framework of the EU FP7 GLOVE project

The Novel “Local Integrity” Approach

70

– Cars used as sensors for signal quality assessment using mass-market receivers

– GNSS observations taken on board of the cars are shared by means of VANET communications

– Collaborative monitoring of GNSS signals in urban scenarios

• Spatial/temporal characterization of local signal degradations

• Computation of “Local Protection Levels” ellipses

– On the basis of an “ensemble monitoring” of the quality of the received signal in a given area and time

– Defined on Along-Track (AT) and Cross-Track (CT) directions

AT CT

• Basic elements (“ingredients”):

Data collection Architecture

71

• Centralized processing of GNSS measurements:

– Collection of measurements taken by many cars in a certain area at certain times

– Digital map (data base) with local information on GNSS signal quality

Processing Facility

Measured GNSS signal quality

Predicted measurement quality (local position confidence)

Sat 1 Sat 2 Sat 3 Sat 4

OBU 2 OBU 4

OBU 1 OBU 3

OBU 5

VANET

Definition of “Local Protection Levels”

72

• How does the signal quality information coming from the central processing facility affect the protection level computation?

• Classic definition of Protection Level:

1

UEREPL · ·

Tk trace

H H

Multiplicative factor related to the integrity risk requirements

Factor related to the satellite

geometry (Dilution of Precision)

User Equivalent Range Error New error model, taking into account

local GNSS signal degradations

UERE,eff

New definition of «Local» Protection Level

• New “Effective User Equivalent Range Error”

–Obtained as an ensemble estimation, computed for each satellite in view, in each position of a grid in a map, at each hour of the day

Measuring the Local GNSS quality

73

• Local measurements: Pseudorange Residuals

– Difference between the measured pseudoranges and the estimated ones, on the basis of the satellite and receiver positions

– Observable quantity, typically used for assessing pseudorange measurement quality in RAIM techniques

– In $GPGRS NMEA sentence

• Effective UERE estimation

– Ensemble average of the sample covariance of the residuals

1

 T T

LS

x H H H y

LS

w Hxy

2UERE,ˆ

4

T

effsat

EN

ww

Outline

74

• Need for GNSS integrity in road applications

• The novel “Local Integrity” approach

– Reference system architecture for the Local Integrity

– Cooperative estimation of the local GNSS degradations

• Experimental proof-of-concept

– Urban tests

• Prototype demonstrator of Local Integrity

Experimental Validation: Urban Field Tests

75

Data collection campaign & post-processing analyses

– Multiple vehicular tests in an urban scenario

– Repeated several consecutive days: to exploit the repeatability of the GPS geometry every 23 hours, 56 minutes

– 7 different receivers (2 survey-grade, 5 mass-market receivers)

– Various local signal impairments:

• Trees along an avenue

• Narrow streets

• 5-6 stores brick building

• Multipath

• Signal blockage

• NLOS

Range residuals are repeatable

76

• Repeatable degradations of range residual measurements

– Along the same path

– Along several days

– Due to the periodicity of the GNSS satellite geometry

11:42:00 11:43:00 11:44:00 11:45:00 11:46:00 11:47:00 11:48:00 11:49:00 11:50:00 11:51:00 11:52:00 11:53:00 11:54:00-50

-40

-30

-20

-10

0

10

UTC time

Range r

esid

uals

[m

]

Range residuals for SVs used in navigation vs UTC time

PRN 05

PRN 07

PRN 08

PRN 10

PRN 15

PRN 21

PRN 24

PRN 28

PRN 09

PRN 26

30

210

60

240

90270

120

300

150

330

180

0

15

30

45

60

75

90

5

8 9

15

26

28

7

10

Skyplot (satellites used in PVT) at UTC time 11:42:00

Two consecutive passes in the same position (1 minute delay)

Range Residuals are Correlated in Space and Time

77

• Remarkable space/time correlation in range residuals resulting highly correlated:

– within about every 15 meters

– within about 5 minutes within the same 15 meters)

• Possibility of building a grid data base (digital map) of averaged residuals for each satellite in view:

– 15 meters spatial resolution

– 5 minutes temporal resolution

157.9

208.6

194.5

54.4

57.3

11.5

6.5

12.6

20.9

34.4

29.3

24.4

18.6

30.0

25.4

16.3

18.6

13.3

20.5

32.2

33.9

27.6

34.9

36.6

Effective UERE 2UERE,ˆ

eff

Outline

78

• Need for GNSS integrity in road applications

• The novel “Local Integrity” approach

– Reference system architecture for the Local Integrity

– Cooperative estimation of the local GNSS degradations

• Experimental proof-of-concept

– Urban tests

• Prototype demonstrator of Local Integrity

Proof-of-concept Demonstrator of Local Integrity

79

Software module implemented on a “car PC” • It parses & processes live GNSS measurements

from a commercial GPS/EGNOS receiver, through NMEA protocol – Ready to be sent to the Central Facility

• It computes the Local Protection Levels, using the range residuals data base along the reference path

• It shows LPLs in real time on a Graphical User Interface on board

Local Integrity: On-Board Demo Video

80

Local protection level: analysis of the results

81

LPL values versus UTC time, as measured during a demo session:

11:05:00 11:10:00 11:15:000

10

20

30

40

50

60

70

UTC time

Loca

l Pro

tect

ion

Leve

ls

Local Protection Levels vs UTC time

Vertical PL

Cross-Track PL

Along-Track PL

Max PL value

95%

AT 72.1 m 20.9 m

CT 30.8 m 24.7 m

Vertical 72.3 m 36.3m

Final remarks and future developments

82

Promising concept for the domain of the connected vehicles, but deeper investigations are needed:

• Refinements of the statistical characterization of the different error sources

– Including detection of non-nominal errors

• Proper calibration of data-base building procedure to different scenarios

– Space and time resolution

• Extensive validation campaign of the data base

• Proper definition of the data communication protocols

– VANET

– Non-VANET (3G, LTE, …)

• Regulatory and standardization aspects

83

Contacts

Gabriella Povero – Gianluca Marucco – Matteo Vannucchi

Navigation Technologies

surname@ismb.it

www.navsas.eu

www.ismb.it