© 2015 Hong Kong R&D Centre for Logistics and Supply Chain Management Enabling Technologies. All rights reserved.

Hong Kong GNSS infrastructure for surveying and navigation, and environment monitoring

Wu ChenDepartment of Land Surveying and

GeoinformaticsHong Kong Polytechnic University

Email: lswuchen@polyu.edu.hk

Background

1. GPS revolutionize the concepts of positioning/navigation/timing (PNT)

2. GPS has become an important infrastructure to support economic development

– Military– Transportation– Telecommunication– Space Industry– Finance – Location Based Services– Surveying– Weather forecasting– Scientific researches

3

Background

• International Developments

– Augmentation systems• To improve performance of GPS

– Accuracy, Integrity, Coverage

• Satellite Based Augmentation Systems (SBAS)– WAAS, EGNOS, MSAS, QZSS, GAGAN, ….

• Ground Based Augmentation systems (GBAS)

– Other Independent GNSS systems• GLONASS (Russian)• Compass (Beidou, China)• Galileo (Europe)• IRNSS (India)

4

Background

• GNSS Based Services – Global Services

• GPS, GLONASS, Beidou (III), Galilieo

– Regional Services

• Compass (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)

5

GNSS Development in Hong Kong

Lands DepartmentGNSS control network“SatRef” Network (12 stations)

Marine DepartmentDGPS system for marine navigationAutomatic Identification System (AIS) for port management

Airport Authority Considering a GBAS system for landing

Hong Kong Polytechnic University 20 year research on GNSS technologiesGNSS ionosphere monitoring networkSpatial water vapour distribution in Pearl Delta region

6

HK GNSS Reference Network （SatRef）

7

• Established in 2003

• 6 land AIS stations to cover HK water

• Provide DGPS correction

• Also

– A DGPS beacon covers 150 nmi

Hong Kong Land-based Automatic Identification system (AIS)

8

Hong Kong Airport

9

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

10

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 forecasting11

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 PolesBeidou

Logistic Application

12

Mobile phones Tested

• Samsung Galaxy S5: GPS/GLO/Beidou

• Samsung Galaxy tab: GPS/GLO/Beidou

• Huawei: GPS

• LG: GPS/GLO

• HTC: GPS/GLO

13

Galaxy S5

3860 3870 3880 3890 3900 3910 39201580

1590

1600

1610

1620

1630

1640

E(m)

N(m

)

Pos err (m)

RTK 0.0

Mobile 3.7

DGNSS 1.3

14

Hua Wei

3860 3870 3880 3890 3900 3910 39201580

1590

1600

1610

1620

1630

1640

E(m)

N(m

)

Pos err (m)

RTK 0.0

Mobile 4.1

DGNSS 2.3

15

16

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

17

Concept of GNSS heighting

18

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

19

20

Height Control PointsNgau Tam Mei

Nam

Shan

So Kwun Wat Tai Mo Shan

Lin Fa Shan

Buffalo Hill

Pyramid Hill

21

Gravity Points in 1990

22

Gravity Points in 2015

Gravity Survey

23

Multiple GNSS Systems

GPS only: 12 GPS+GLONASS+Beidou: 33

24

GNSS Positioning in difficult environments

Distance (mm) Height (mm)

BeiDou - -

GLONASS with BeiDou - -

GPS - -

GPS with BeiDou 4 -98

GPS with GLONASS 761 -79

25

Field Experiments

GPS/GLONASS

GPS/Beidou/GLONASS

27

Spatial distribution of water vapor

28

29

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

20 22 0 2 4 6 8 10 12 14 16 185

6

7

8

9

10

11

12

1

2

3

4

Local Time (hour)

Month

TECu/min

0

1

2

3

4

5

6

7

8

9

10

ROTI enhancement

20 22 0 2 4 6 8 10 12 14 16 18 5

6

7

8

9

10

11

12

1

2

3

4

Local Time (hour)

Month

H

0

100

200

300

400

500

600

700

800

900

1000

Frequent nighttime scintillations

Hourly occurrence index: ROTI > 0.5 TECu/min (existence of ionospheric irregularities)

Characteristics of scintillations in Hong Kong

— Hourly amplitude scintillation (S4)

30

Summary: Hong Kong GNSS Infrastructure

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

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

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

• Real-time Ionosphere monitoring– Support DGNSS (accuracy and integrity)

• Real-time 3D water vapour observation

31

Thank you

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