The Impact of the new GPS Signals on Positioning Accuracy for Urban Bus Location Based Services

258 Pages·2017·11.06 MB·English

by  El Hajj, Mireille

The Impact of the new GPS Signals
on Positioning Accuracy for Urban
Bus Location Based Services

Mireille Elhajj, BSc (Business), MSc (Finance), MSc (Transport)
April 2017

Submitted in part fulfilment of the requirements for the degree of Doctor of
Philosophy of Imperial College London

Centre for Transport Studies
Department of Civil and Environmental Engineering
Imperial College London

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Declaration of contribution

In the process of undertaking the research presented in this thesis, I have received
supervisory support and advice from my supervisor Professor Washington Ochieng,
as enshrined in the procedures of Imperial College London. The data used in this
thesis were captured in collaboration with a number of colleagues in the Centre for
Transport Studies (CTS) with, in some cases, the support of Transport for London
(TfL). The subsequent management and usage of the data including processing,
analysis and interpretation are the result of my own efforts.
A part of the contributions from the others declared above, I certify that I personally
carried out the research presented in this thesis, and where relevant any reference
to the work of others is acknowledged by appropriate reference to the sources.

Mireille Elhajj

February 2017

The copyright of this thesis rests with the author and is made available under a
Creative Commons Attribution Non-Commercial No Derivatives licence. Researchers
are free to copy, distribute or transmit the thesis on the condition that they attribute it,
that they do not use it for commercial purposes and that they do not alter, transform
or build upon it. For any reuse or redistribution, researchers must make clear to
others the licence terms of this work.

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Acknowledgements
I would like to thank my supervisor Professor Washington Ochieng for all the help
and guidance he provided me during my journey to complete my thesis. I would also
like to thank all the staff and fellow PhD students within the Centre for Transport
Studies (CTS) and the Department of Civil and Environmental Engineering at
Imperial College London, for their help and comradeship during the period of my
research.
Particular thanks are due to Dr Shaojun Feng for his help with data capture, and Dr
Xin Zhang and Mr Zhenjun Zhang for their assistance with aspects of the software
used in the thesis. I would also like thank Dr Manela Mauro of Transport for London
(TfL) for his assistance with data capture and discussions on location based services
for bus operations, and the initiation of the survey of the major urban bus operators.
Gratitude is also due to colleagues from the Railway and Transport Strategy Centre
(RTSC) within the CTS for their help with execution of the survey of bus operators.
Finally, sincere thanks to my family and friends for their unwavering support and
encouragement in good and difficult times during the conduct of this research.

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Abstract
Increased bus patronage has the potential to facilitate the achievement of transport
sustainability in cities in the developed and developing countries by alleviating
congestion and its consequences including delays and pollution. However, this
requires bus-friendly policies and a significant improvement in the efficiency of urban
bus operations. Such operations consist of a large number of location based
services such ‘countdown’ which requires the computation of bus arrival times at bus
stops. However, to date there is a lack of agreement globally on the location based
services and their key performance indicators expressed in the form of the required
navigation performance parameters of accuracy, integrity (quality of or confidence in
the position accuracy), continuity of service, and service availability. As a result of
this, there is currently no optimal positioning system specification for bus operations.
This thesis addresses these two issues and contributes to the field by firstly creating
a comprehensive list of location-based services together with the required navigation
performance for some of the applications. This is through a comprehensive literature
review, consultation with a subject matter expert, and augmentation with, for the first
time, a global survey of the major bus operators. Secondly, by demonstrating that a
significant improvement in positioning accuracy is achievable with multi-constellation
differential positioning. This is achieved through a comparative analysis of GPS only
and augmentation with GLONASS and local differential positioning. Thirdly, the
benefits of the new signals are demonstrated in the measurement and position
domains, using established and novel mathematical models.
The thesis analyses in detail the measurement qualities of the legacy and new
signals in the measurement and position domains. The results of the former
demonstrate the superiority of the L5 signal both in terms of signal strength and
measurement precision, over the legacy L1 coarse acquisition (C/A) code
measurements, with the new L2C as the weakest. The results of the position domain
analysis show a significant improvement in positioning accuracy over the use L1 C/A
code measurements alone, as a result of the mitigation of the ionospheric error
through the combined use of the L1 C/A and L2C code measurements. The
improvements in 3D positioning accuracy at the 95th percentile range from 22% (6m)
in the clean (unobstructed environment) to 48% (13.66m) in the urban environment.
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The corresponding 2D horizontal positioning accuracy at the 95th percentile are
3.33m and 9.03m respectively. These improvements would not only enable more of
the location based services to be supported but also facilitate the achievement of
higher accuracy performance when using carrier phase measurements through
enhanced ambiguity resolution.

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List of Acronyms
AIM Autonomous Integrity Monitoring
AL Alarm/Alert limit
APTS Advanced Public Transport Systems
AOD Age-Of-Data
ATIS Advanced Traveller Information Systems
ATMS Advanced Traffic Management Systems
AVCS Advanced Vehicle Control Systems
BDS Beidou Navigation System
BOC Binary Offset Carrier
C/A Coarse Acquisition
CDMA Code Division Multiple Access
CVO Commercial Vehicle Operations
DIF Differential positioning
DoD Department of Defence
DOF Degrees of Freedom
DOP Dilution of Precision
DR Deduced or Dead Reckoning
ECEF Earth Centred Earth Fixed
ECI Earth Centred Inertial
EGNOS European Geostationary Navigation Overlay Service
ESA European Space Agency
FAA Federal Aviation Administration
FDMA Frequency Division Multiple Access
FEC Forward Error Correction
FOC Full Operation Capability
GA Ground Antenna
GBAS Ground Based Augmentation Systems
GDOP Geometric Dilution of Precision
GEO Geostationary Earth Orbiting
GIC GNSS Integrity Channel
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GTO GPS-Galileo Time Offset
GLONASS Globalnaya Navigatsionnay Sputnikovaya Sistema
GTRF Galileo Terrestrial Reference Frame
GNSS Global Navigation Satellite System
GPS Global Positioning System
GPS-JPO GPS – Joint Program Office
HDOP Horizontal Dilution of Precision
HMI Human Machine Interface
iBIS iBUS Information System
iBUS Intelligent BUS
IGS International GNSS Service
INS Inertial Navigation System
IMU Inertial Measurement Unit
IGSO Inclined Geosynchronous Satellites Orbits
IUP Intelligent Urban Positioning
ITRF International Terrestrial Reference frame (ITRF)
ITS Intelligent Transport Systems
LADGNSS Local Area Differential GNSS
LBS Location Based Services
LAN Local Area Network
LHCP Left Hand Circular Polarization
LORAN Long Range Navigation
MDB Minimum Detectable Bias
MEMS Micro-Electro-Mechanical Systems
MEO Medium Earth Orbit
MCS Master Control Station
MS Monitor Stations
NANU Notice Advisory to Navstar Users
NANUI Notice Advisory to Navstar User Interface
NDGNSS Network Differential GNSS
NLES Near Land Earth Station
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NLOS/LOS Non Line of Sight / Line of Sight
NMEA National Marine Electronics Association
NOTAM Notice to Airmen
NDU Navigation Data Unit
PDOP Position Dilution of Precision
PE Position Error
PF Probability of Failure
PFA Probability of False Alert
PL Protection Level
PMD Probability of Missed Detection
PNT Positioning, Navigation and Timing
PPM Parts Per Million
PPP Precise Point Positioning
PPS Precise Positioning Service
PRN Pseud-Random-Noise
PRS Public Regulated Service
QZSS Quasi-Zenith Satellite System
RAIM Receiver Autonomous Integrity Monitoring
RF-ID Radio Frequency IDentification
RHCP Right Hand Circular Polarization
RINEX Receiver INdependent EXchange (RINEX)
RNP Required Navigation Performance
RMS Root Mean Square
RMSE Root Mean Square Error
NRTK Network Real-Time Kinematic positioning
RSS Received Signal Strength
SAIM Satellite Autonomous Integrity Monitoring
SaPPART Satellite Positioning Performance Assessment for Road Transport
SBAS Space Based Augmentation Systems
SiS Signal-in-Space
SMS Short Message Service
SNR Signal-to-Noise
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SoL Safety-of-Life
SOOP Signals of Opportunity
SPS Standard Positioning Service
SSE Sum of the Squared Residuals
TDMA Time Division Multiple Access
TDOP Time Dilution of Precision
TEQC Translation, Editing and Quality Checking
TfL Transport for London
TOA Time of Arrival
TOF Time of Flight
TSD Total Slant Delay
TTA Time to alarm
TT&C Tracking, Telemetry and Control
UITP International Association of Public Transport
URA User Range Accuracy
UERE User Equivalent Range Error
URE Use Range
UTC Universal Coordinated Time
VDOP Vertical Dilution of Precision
VPL Vertical Protection Level
WADGNSS Wide Area Differential GNSS
WAN Wide Area Networks
WGS84 World Geodetic System 1984
WiFi Wireless Fidelity
WLAN Wireless Local Area Networks
WMAN Wireless Metropolitan Area Network
WPAN Wireless Personal Area Network
WWAN Wireless Wide Area Network
WSSE Weighted Sum of the Squared Errors
ZHD Zenith Hydrostatic Delay
ZWD Zenith Wet Delay

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Table of Contents
1. INTRODUCTION ............................................................................................... 24
1.1 Background .................................................................................................. 24
1.2 Aims and objectives ..................................................................................... 28
1.3 Structure of the thesis .................................................................................. 29
2. URBAN BUS OPERATIONS ............................................................................. 31
2.1 Location based applications and requirements ............................................ 35
2.2 Urban bus operations location based services and requirements ................ 37
2.2.1 Applications/Services ............................................................................. 38
2.2.2 Required Navigation Performance ......................................................... 45
2.3 Functional architecture of Bus operations system ........................................ 48
2.4 Urban bus location determination functional architectures ........................... 52
2.5 Summary ...................................................................................................... 54
3. POSITIONING TECHNOLOGIES FOR BUS OPERATIONS ............................ 55
3.1 Space-based positioning systems ................................................................ 55
3.1.1 GNSS ..................................................................................................... 56
3.1.2 Augmented GNSS .................................................................................. 73
3.1.3 Non-GNSS terrestrial based augmentation ............................................ 77
3.1.3.2 Inertial Navigation Systems (INS) ....................................................... 79
3.1.4 Integrated positioning systems ............................................................... 85
3.1.5 The current bus operations technology landscape ................................. 86
3.1.6 Summary and proposed architecture for urban bus operations .............. 87
4. FUNCTIONAL MODELS OF GNSS ............................................................. 89
4.1 GNSS Fundamentals ................................................................................... 89
4.1.1 Reference Systems, Reference Frames and Coordinate Systems ........ 89
4.1.2 Satellite Orbit .......................................................................................... 92
4.2 GPS pure observables ................................................................................. 93
4.2.1 Derivation of the pseudo-range observation equation ............................ 93
4.2.2 The Carrier Phase Observable ............................................................... 96
4.2.3 The Doppler Observable ........................................................................ 99
4.3 Measurement Errors ................................................................................... 100
4.3.1 Satellite Clock Error .............................................................................. 100
4.3.2 Ephemeris Error ................................................................................... 100
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