Workshop on GNSS for Policy and Decision Makers
21st January 2022

Basic GNSS Introduction and Applications

Dinesh Manandhar, Associate Professor (Project)
Center for Spatial Information Science (CSIS), The University of Tokyo
dinesh@csis.u-tokyo.ac.jp2022/02/02 8:23 PM

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 1

Fundamental Problem

How to go from A to B?

• How to know my location precisely ?
• In any condition• At any time
• Everywhere on earth (at least outdoors!)• How to navigate to the destination?

A• Guidance or Navigation• How to synchronize time globally?
• Mobile phones• Financial Institutes
Where am I
on the Earth?
350 40’ 41”
1390 39’ 40”

B
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Source: Google Maps
Slide : 2

Navigation Types• Landmark-based Navigation• Stones, Trees, Monuments• Limited Local use• Radio-based Navigation• LORAN, OMEGA• Subject to Radio Interference, Jamming,
Limited Coverage• Celestial-based Navigation• Stars, Moon
• Complicated, Works only at Clear Night• Sensors-based Navigation• Dead Reckoning• Gyroscope, Accelerometer• Compass, Odometer• Error accumulate quickly (Drift Error)• Satellite-based Navigation or GNSS
• TRANSIT (not used anymore)• GPS, GLONASS, GALILEO, QZSS(Michibiki), BEIDOU (COMPASS), NavIC(IRNSS)• Global service, QZSS and NavIC are regional• High Accuracy & Reliability

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 3

What is GNSS?
L5/E5/B2/L3

L2

L6/E6/B3

L1/E1/B1• GNSS or Global Navigation Satellite System is an acronym used to represent
all navigation satellite systems such as

Satellite

Country

Coverage

GPS

USA

GlobalGLONASS

RussiaGlobalGalileoEuropeGlobal

BeiDou (BDS)

China

GlobalQZSS (Michibiki)

Japan

Regional

NavIC

India

Regional GPS and GLONASS have signals for civilian and military usage
 Military signals are encrypted and not available for civilian use
 Galileo and BeiDou also have Open and Restricted Signals
 All civilian signals are freely available Technical information for civilian signals are made public Necessary to develop a receiver Its called ICD (Interface Control Document) or IS (Interface
Specification)
https://gssc.esa.int/navipedia/images/c/cf/GNSS_All_Signals.png
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 4

GPS (USA)

Source: This slide is taken from “GPS Programme Update and International Activities to Protect GNSS Spectrum”
Link: https://www.unoosa.org/oosa/en/ourwork/icg/activities/2022/CSISTokyo/presentations.html
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp Please refer original document for detail informationSlide : 5

GLONASS (Russia)

These slides were taken from ICG Website.
Pleaserefer CSIS,
the original
presentationmaterial at
Please refer original document for detail information
DineshManandhar,
The Universityof Tokyo, dinesh@csis.u-tokyo.ac.jp
https://www.unoosa.org/documents/pdf/icg/2021/ICG15/01.pdf

Slide : 6

Galileo (Europe)

Please refer original document for detail information
Source: This slide is taken from “Galileo Status Update”
Link: https://www.unoosa.org/oosa/en/ourwork/icg/activities/2022/CSISTokyo/presentations.html
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 7

BeiDou (China)

Source: This slide is taken from “BeiDou Navigation Satellite System Development and High-Accuracy Applications”,
Link: Introduction to BeiDou at https://www.unoosa.org/oosa/en/ourwork/icg/activities/2022/CSISTokyo/presentations.html
Please refer original document for detail information Slide : 8

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

QZSS (Japan)

Source: This slide is taken from “Introduction to QZSS and Applications”
Please refer original document for detail information
Link: https://www.unoosa.org/oosa/en/ourwork/icg/activities/2022/CSISTokyo/presentations.html
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 9

NavIC (India)

Source: This slide is taken from “NavIC System and Applications: Status and Update”
Link: https://www.unoosa.org/oosa/en/ourwork/icg/activities/2022/CSISTokyo/presentations.html Please refer original document for detail information
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 10

Systems Related with Navigation
Navigation Satellite Systems
GPS, GLONASS, Galileo, BeiDou, QZSS, NavIC

Augmentation Systems
SBAS or GBAS
Satellite Based Augmentation Systems(SBAS)PVT Computation Engine(Position, Velocity and Time)
Ground Based Augmentation Systems(GBAS)PVT Solutions with
Enhanced Accuracy and Reliability

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 11Satellite Based Augmentation System (SBAS)• Satellite Based Augmentation System (SBAS) are used to augment GNSS Data
• Provide Higher Accuracy and Integrity• Correction data for satellite orbit errors, satellite clock errors, atmospheric correction
data and satellite health status are broadcasted from satellites• SBAS Service Providers
•
•
•
•
•
•
•
•
•
•

WAAS, USA (131,133,135,138)
MSAS, Japan (129,137)
EGNOS, Europe (120,121,123,124,126,136)
BDSBAS, China (130,143,144)
GAGAN, India (127,128,132)
SDCM, Russia (125,140,141)
KASS, Korea (134), Also Navigation System
AUS-NZ, Australia (122)
NSAS, Nigeria, (147)
ASAL, Algeria (148)
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

PRN code numbers are given in the bracket

Slide : 12

GNSS Signals received
by a receiver

Satellite signal power level

Position Output

Altitude

GNSS Satellites visible inthe sky where receiver islocatedTime in UTC

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 13

GNSS Signals received
by a receiver

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 14

Raw data necessary tocompute position

DopplerSatellite signal power level

Position Output

Altitude

GNSS Satellites visible inthe sky where receiver islocated

Code Phase Data

Time in UTC

Carrier Phase Data

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 15

JAKARTABANGKOK

MANILAKUALALUMPUR

Ho Chi MinhTOKYO

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

We do not have BeiDou data in Kualalumpur and Ho Chi Minh stations because of license limitation in the receiver

Slide : 16

GPS Skyplots: Tokyo, Jakarta and Maputo
Tokyo Base-Station

Jakarta Base-Station

Maputo Base-Station

17
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 17

How does a GPS/GNSS Receiver Work?

2022/02/02 8:23 PM

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 18

GNSS: How does it work?
Determine the Distance using Radio Wave
0ms

Assume that the Satellite Transmits Signal at 0ms.
If Receiver receives the same Signal after 67ms,
Distance = 67x300,000 = 20,100Km

25ms
50ms

0ms
Satellite with a known positiontransmits a regular time signal.

75ms

25ms
50ms

Distance = (Reception Time - Transmission time) × Speed of light
Speed of Light: 300,000 km/s
2022/02/02 8:23 PM

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 19

GNSS: How does it work?
Principle of Satellite-based Navigation(xk, yk, zk)

Receiver generates its own GPS signal similar to the signal
coming from the satellite for each satellite
Its called Replica Signal
The Replica Signal includes PRN Code and Carrier Signal
This Replica Signal is moved forward and backward to
match with the incoming signal

𝜌𝑘 =𝑥0 − 𝑥𝑠𝑘2+ 𝑦0 − 𝑦𝑠𝑘2+ 𝑧0 − 𝑧𝑠𝑘2+𝜀(x0,y0,z0)

If k ≥ 4, solve for x, y, z and errors including clock bias 𝜀2022/02/02 8:23 PM∆t

Correlation between Incoming Signal andReceiver Generated Signal

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 20

Pseudorange (Code-Phase Measurement) - 1
Transmission
Time

Pseudorange = (Reception Time – Transmission time) x Speed of Light

Signal propagation at the speed of light

About 20,000 km

Reception
Time

Transit time

A GPS receiver measures the signal transmission timefrom the code phase at signal reception time.
2022/02/02 8:23 PM

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 21

How to Improve GPS Accuracy?

2022/02/02 8:23 PM

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 22

Error sources
Satellite Orbit Error
V = 4km/s

Satellite Clock Error

Ionospheric Delay
50 – 200Km

Tropospheric Delay
10Km
Multipath

Thermal Noise

Receiver Clock Error
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 23

GPS Position Accuracy
How to achieve accuracy from few meters to few centimeters?
metercentimeter

50 cm grid

50 cm grid

5 cm grid

SPP (Single Point Position)

DGPS (Differential GPS)
Code-phase observation

RTK (Real Time Kinematic)
Carrier-phase observation

2022/02/02 8:23 PM

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 24

Errors in GPS Observation (L1C/A Signal)
Error Sources

One-Sigma Error , mSatellite Orbit
Satellite Clock

Total
2.0
2.0

DGPS
0.0
0.0

Ionosphere Error
Troposphere Error
Multipath

4.0
0.7
1.4

0.4
0.2
1.4

Receiver Circuits

0.5

0.5

Comments
Common errors are removed

Common errors are reduced

If we can remove common errors, position accuracy can be increased.
Common errors are: Satellite Orbit Errors, Satellite Clock Errors and Atmospheric Errors (within few km)
Values in the Table are just for illustrative purpose, not the exact measured values.
Table Source : http://www.edu-observatory.org/gps/gps_accuracy.html#Multipath
2022/02/02 8:23 PM

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 25

How to Improve Accuracy?
• Both Code-Phase and Carrier-Phase observations are necessary• Carrier-phase provides centimeter level resolution• Need to remove or minimize the following errors:• Satellite Related Error• Satellite orbit errors• Satellite clock errors• Space Related Errors• Ionospheric errors• Tropospheric erros• Receiver Related Errors• Receiver clock error• Receiver circuit related

2022/02/02 8:23 PM

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 26

High-Accuracy Observation Methods• Basically three types of Observation• DGPS (Differential GPS)• Code-phase observation• Requires Base-station (Reference Station)• RTK (Real Time Kinematic)• Code-phase and Carrier-Phase Observation• Requires Base-station (Reference Station)• PPP (Precise Point Positioning)• Code-phase and Carrier-phase observation• Does not require base-station

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 27

Which Method: DGPS, SBAS, RTK, PPP?

http://www.novatel.com/an-introduction-to-gnss/chapter-5-resolving-errors/
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

28 Slide : 28

How to Remove or Minimize Common Errors?
Use Differential Correction
30

Recommended Base-length < 40Km
Send Observation Data to Roverfor Real-Time Position
Base-Station

Rover
For RTK, both base and rover receivers need toAntenna is installed at aUser in the Field
use data from the same satellites
known-position(Either fixed or moving)Base-station Antenna position
Use RINEX data for post-processing
shall be known in advance2022/02/02 8:23 PM

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 29

How to Remove or Minimize Common Errors?
Principle of QZSS MADOCA and CLAS Services
QZSS

GPS

Currently, MADOCA provides correction
data for GPS, GLONASS and QZSS.
It will be extended for Galileo in future.

Correction Data:
Satellite Orbit Error of GPS and Other Satellites
Satellite Clock Error of GPS and Other Satellites

Base-Station is not required.
The Rover receiver should be able to receiver MADOCA
signal in L6 band.
MADOCA correction data is also available online.

Rover
2022/02/02 8:23 PM

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 30

GNSS Applications

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 31

Lots of Opportunities for these GNSS Applications…..

Legal & Law
Enforcement

Pay-As-YouDrive

Agriculture

Toll Fee

Precision
Farming

Geo-Fencing

ITS / ADAS

Emergency &Safety Services

Geo-Security

Auto-Driving

SoL, e-Call

Illegal Fishing

V2V / V2X

ERA-GLONASS

Transport

MedicalHealthServices

Early Warning

VehiclesPeople Flow

ERP

Surveying
MappingRailGIS
Tax Collection

UAV / UMV

Insurance

IoT

Alternate forFuel Tax
Collection

M2M

SecuredTransport ofDangerous
Goods

AI

Robotics

TimingApplications

Aviation

LBS

Space

Game

Telecom
Finance

Power Grid

Entertainment
Scientific
Applications

Advertisement
MarketingSpace Weather

Supply-Chain

VLBIManagement

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 32

Road Pricing : ERP to ERP 2.0 (Singapore)

ERP  ERP2.0
ERP is based on Gantry System
Requires construction of huge structures

ERP 2.0 is based on Satellite System (GNSS)

Source: https://onemotoring.lta.gov.sg/content/onemotoring/home/driving/traffic_information/traffic-smart.html
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 33

Dynamic Road Pricing (DRP) based on GNSS
• Road Usage Charging• Pricing is variable and based on•

Distance, time, location,•

Vehicle type, lane and occupancy•

Traffic congestion condition• Reward road users for using alternate routes toavoid congested route• Payback the drivers who help to minimize traffic
congestion• No Physical Toll Gates• GPS-based system is used for Location, Distance andLane occupation• Can be implemented on any road section•

Not limited to only highways, express ways or toll roads• Global Seamless Implementation• The same system can be implemented globally• The same In-vehicle device can be used globally•

Single system for smooth cross-border operation•

Once a border is crossed, charging or rewarding rates canbe updated automaticallyDinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 34

GNSS for Precise Farming
Before and after seedling, the tractor has to irrigate, put
fertilizer and spray pesticides where there are plants.
If they are put far from the plant, it will affect the yield.

This requires few centimeter level of accuracy so that thetractor can automatically perform the job at different
stages of plant growth and harvesting.
GNSS is a core system to provide this level of accuracy.

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 35

Fishing Boat Monitoring

Fishing boats in Bali, Indonesia

Queensland Fisheries in Australia requires every boat to have GPS tracking device
https://www.youtube.com/watch?v=2qWTAZ8hmOY&t=36s

 Monitoring of Fishing Boats is necessary to fishing industry.
 This will help the fishermen to generate more income in long-term.
 Over-fishing, Illegal fishing shall be stopped to protect marine ecology and bio-diversity.

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 36

Slide from QZSS Presentation by S. Kogure, UTokyo/ICG GNSS Training, 11 – 14 January 2022
Link: https://www.unoosa.org/oosa/en/ourwork/icg/activities/2022/CSISTokyo/presentations.html
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 37

QZSS Early Warning System (EWS) : System to Test EWS
Disaster and Crisis (DC) Management Report (in Japan)
QZSS

EWS Message
Decoding
GNSS(Pos. Vel.,Time)

2
Coding
Display EWS
Message

Coding Interface
Data Communication
Link

QZSS Receiver

QZSS Control Office
Japan

3

1

4

EWS Test Message

Data
Link

5

6

Flashing light

Siren System

7

Teams generate sample EWS message
See documents: EWS_Format.pdf
EWS_Message_Example.pdf

Minimum Requirement as MVP (Minimum Viable Product) for PoC level Prototype:
Item (1) : Generate sample test EWS message
Item (2) : Read EWS message from Spresense device and display in a PC

Alarm, Evacuation
Guidance

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Showing message
on signage display
Slide : 38

eCALL / ERA-GLONASSeCALL (Europe)

https://www.youtube.com/watch?v=yj0j9aV7Km4ERA-GLOANASS (Russia)

https://www.youtube.com/watch?v=pJkhBLKs2lc

90% of accident victims survive if help is available within 9 minutes of accidents
Only 15% can be saved after 18 minutes – ERA-GLONASS

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 39

Reference Slides

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 40

GPS L1C/A Signal Structure• Carrier Signal• It defines the frequency of the signal• For example:• GPS L1 is 1575.42MHz, L2 is 1227.60MHz and L5 is 1176.45MHz• PRN Code• Necessary to modulate carrier signal• Used to identify satellite ID in the signal• Should have good auto-correlation and cross-correlation properties• Navigation Data
• Includes satellite orbit related data (ephemeris and almanac data)• Includes satellite clock related information (clock errors etc.)• Includes satellite health information
2022/02/02 8:23 PM

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 41

GPS L1C/A Signal Structure (Satellite Side)
x154

L1 Carrier, 1575.42Mhz
Carrier Signal∑
X1, Clock10.23Mhz

x1/10

PRN Code, 1.023Mhz
PRN Code

Atomic ClockRb or Cs Clocks

L1 Band GPS Signal

x1/204600

Navigation Data, 50Hz
Navigation Data

2022/02/02 8:23 PM

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 42

Pseudorange (Code-Phase Measurement) - 2

1-sequence of PRN Code is 1023 bits, 1ms long.
This corresponds to 300Km
1-bit or chip corresponds to 1/1023 ms.
This is about 293m (say 300m) in distance.
In the receiver, signals are resampled at certain frequency, say 10MHz.
This means every chip will be further divided into 10 smaller chips.
If it is possible to detect code phase at 1/10 of this sampled chip, then range
measurement accuracy would be about 300/10/10 = 3m.
However, there are various types of noises and this accuracy may not be possible.
Normally, GPS L1C/A guarantees an accuracy within 10m.
Thus, using Code-Phase (PRN code) measurement, the accuracy will be limited to few
meters level.

2022/02/02 8:23 PM

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

2mSlide : 43

PRN (Pseudo Random Noise) Code• PRN Code is a sequence of randomly distributed zeros and ones that is one millisecond long.
• This random distribution follows a specific code generation pattern called Gold Code.
• There are 1023 zeros and ones in one millisecond.

• Each GPS satellite transmits a unique PRN Code.
• GPS receiver identifies satellites by its unique PRN code or ID.

• It continually repeats every millisecond• The receiver can detect where the PRN code terminated or repeated.
• A unique sequence of bits indicates start of a PRN code.

• It helps to measure signal transit time and compute pseudorange between the receiver and the satellite• Its also called C/A (Coarse Acquisition) code in GPS
1ms / 1023

Unique Sequence at thestart of the PRN code0 1 0 1 0 0 11 0 1 0 0
1ms

2022/02/02 8:23 PM

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 44

Carrier-Phase Measurement – 1• Carrier-Phase measurement is done by counting the number of cycles coming from the satellite to thereceiver.
• However, there are many complexities in measuring total number of cycles (N) from the satellite to thereceiver.
• This is called integer ambiguity• This is due to the fact that all cycles are the same and there are no headers to tell the receiver when a new cycle has
arrived after number of cycles as in PRN code.
••

A PRN code has a header to tell the receiver that this is the beginning of the PRN code that is 1023 chips long.
There are algorithms to solve this problem of ambiguity resolution.

• One complete cycle for GPS L1 band is 19cm long.
• Thus, if we can measure one wavelength, we can get 19cm accuracy• If we can measure 1/10th of a cycle, we get about 2cm accuracy.
• Thus, Carrier-Phase measurement can provide centimeter level accuracy.

2cm

19cm

2022/02/02 8:23 PM

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 45

21,000

600

300

000

Code-Phase (PRN Code) vs. Carrier-Phase Measurement

19cm

Code-Phase Measurement
Measuring distance between the satellite and the receiver with a tapethat has distance markings as well as distance values written. So that we
can measure correct distance.

Carrier-Phase Measurement
Measuring distance between the satellite and the receiver with a tapethat has distance markings but distance values are not written. We only
know that each distance marker is 19cm apart. So, we need to count at
certain point the number of cycles separately that’s coming to thereceiver. This is called integer ambiguity solving.

Only provide meter level accuracy

Provides centimeter level accuracy

Simple and required measurement. It’s part of signal demodulation
process. So this can’t be avoided.

Counting of number of cycles (solving integer ambiguity) is not required
if carrier-phase based measurement such as RTK or PPP is not required.

2022/02/02 8:23 PM

Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 46