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Development of Hong Kong GNSS infrastructure

Wu Chen Department of Land Surveying and Geoinformatics

(LSGI) Hong Kong Polytechnic University

Hong Kong

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Research Areas

• Research Areas – GNSS Positioning and applications – GNSS Reflectometry and Remote Sensing – Seamless indoor/outdoor Positioning Technologies – SLAM for 3D modelling and positioning

• Wide cooperation with Academic Institutes,

Industries, and Government Agencies • Research Funding for last 4 years: 40M • Donations from Industry in last 4 years: 6M

2

Work with Government Agencies

• Lands Department

• Civil Engineering and Development Department

• Police Department

• Hong Kong Post

• Logistics and Supply Chain Management Research Centre

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Close Link with Industries

• 腾讯 • 华为 • 中海达 • 北斗星通 • 合众思壮 • 武汉北斗研究院 • Motorola • Autotoll • ESRI (HK) • Leica

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GNSS Infrastructure Background

• GNSS Based Services – Global Services

• GPS, GLONASS, Beidou (III), Galilieo

– Regional Services

• Beidou (I, II), IRNSS

• Satellite Based Augmentation Systems (SBAS)

– WAAS, EGNOS, MSAS, QZSS, GAGAN, ….

– Local Services

• Ground Based Augmentation systems (GBAS) (Aviation)

• DGPS Services (Marine)

• GNSS RTK Network (Surveying)

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Lands Department

GNSS control network “SatRef” Network (18 stations)

Marine Department DGPS system for marine navigation Automatic Identification System (AIS) for port management

Airport Authority Considering a GBAS system for landing

GNSS Development in Hong Kong

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HK GNSS Reference Network （SatRef）

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Upgraded to multi-GNSS Receivers in 2015

Problems identified

1. HK SatRef has been established for many years, but the users are mainly surveyors

2. SatRef was based GPS only, need to be enhanced with multiple GNSS to improve performance and reliability

3. Hong Kong suffers from ionosphere anomaly effects

4. High rise buildings in urban area: strong multipath and low availability

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Develop an GNSS based infrastructure to support Economic Development in HK

1. Develop multiple PNT services to support Hong Kong economic development and for the public to obtain reliable and accurate positioning data at low cost

2. Utilizing multiple GNSS positioning systems (i.e. GPS, Beidou, GLONASS), together with ground based augmentation systems, to solve urban positioning problem, and to provide reliable and secured positioning services

3. Develop better algorithms and models to improve positioning performance under the disturbances of ionosphere to improve accuracy and reliability of PNT services

4. Real-time Ionosphere Monitoring to support GNSS integrity and DGNSS services

5. 3D Water Vapour observation for weather forecasting

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Collaboration with Government Agencies and Industries

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Hong Kong Positioning Infrastructure

Users Development

PolyUl

HK Post

HK PD

Autotoll

LSCM

HK LD

10 Companies HK CEDD

HK LD

Reliable 3D RTK services

• Platform of multiple GNSS to support RTK centimeter positioning

– Establish an multiple GNSS network (include GPS/Beidou/…)

– Provide reliable RTK positioning service

– High quality geoid height at user site

– Support single-frequency RTK

server

Multiple GNSS network

Other users

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Concept of GNSS heighting

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Gravity Survey Arrangement

• Gravity Survey: 635 points (46 old gravity points)

• GPS/levelling control points: 136 points

• Evaluation of gravity survey results: 69 check points, accuracy is 0.02mgal

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Hong Kong Geoid Model (1 cm)

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Multiple GNSS Systems

GPS only: 12 GPS+GLONASS+Beidou: 33

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GNSS Positioning in different environments

Distance (mm) Height (mm)

BeiDou - -

GLONASS with BeiDou - -

GPS - -

GPS with BeiDou 1547 -3522

GPS with GLONASS - -

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Field Experiments

GPS/GLONASS

GPS/Beidou/ GLONASS

DGNSS Ambiguity Float Solution

Ambiguity Fixed Solution

System Architecture for DGNSS

GPS GLONASS

GPS enabled

Mobile Device

Lands Department

Active GNSS network

Server Platform

RTCM

GNSS observation

Measurements or

NMEA Data

Correction Data

(∆X, ∆Y, ∆Z)

Reference Poles Beidou

Logistic Application

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Mobilephone DGNSS Tests

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1500 1510 1520 1530 1540 1550 1560-1.166

-1.165

-1.164

-1.163

-1.162

-1.161

-1.16

-1.159

-1.158x 10

4

E(m)

N(m

)

Pos err(m) Mean Rms

RTK

Mobile 4.0 4.1

DGNSS 1.5 1.9

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Vehicle Test

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Immigration

Department Direct

Path

Reflected

Path

Direct

Path

Blocked

(NLOS) N

E

Multipath Mitigation for mobile users

Paths of All GNSS Satellites

N

E

GNSS: urban areas, Multipath Mitigation

• Urban area: multipath, errors can reach a few tens meters

• Using multipath mitigation algorithms: <10 m

• Tests in Mongkok

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Wanchai: Multipath Mitigation

N E

NMEA (red)

26.0 12.5

Multipath mitigation (Green)

7.1 6.5

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Spatial distribution of water vapor

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Electron Density Distribution in HK

• Reconstructed electron density distributions on 1 March 2011

(12:00 LT and 14:00 LT )

latitude (degree)

He

ight

(km

)

Electron Density Distributions over Hong Kong Date:March 1, 2001 Local Time: 14:00-15:00 Electron Density Unit: Ne/cm-3

14.50 17.00 19.50 22.00 24.50 27.00 29.50 32.00

200.00

300.00

400.00

500.00

600.00

700.00

800.00

900.00

923609

1.75668e+006

2.58976e+006

3.42283e+006

4.2559e+006

latitude (degree)

He

ight

(km

)

Electron Density Distributions over Hong Kong Date:March 1, 2001 Local Time: 12:00-13:00 Electron Density Unit: Ne/cm-3

14.50 17.00 19.50 22.00 24.50 27.00 29.50 32.00

200.00

300.00

400.00

500.00

600.00

700.00

800.00

900.00

923609

1.75668e+006

2.58976e+006

3.42283e+006

4.2559e+006

Summary: Hong Kong GNSS Infrastructure

• Develop DGNSS services for HK – Correction accuracy < 0.5 m – Mobilephone ~ 2 m

• Dense Built-in Areas – Accuracy < 10 m for mobile users

• Develop high precision HK Geoid model – Accuracy ~ 1 cm

• Develop Multiple GNSS RTK service – Accuracy ~ 1-2 cm (3D)

• Ionosphere monitoring – Support DGNSS (accuracy and integrity)

• water vapour observation (support weather forecasting)

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Thank you

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