Introduction to GNSS
(Global Navigation Satellite System)
Dinesh ManandharCenter for Spatial Information Science
The University of Tokyo
Contact Information: dinesh@csis.u-tokyo.ac.jp

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

Slide : 1

Part - A

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

Slide : 2

Fundamental Problem

Where am I
on the Earth?
350 40’ 41”
1390 39’ 40”• How to know my location precisely ?
• In any condition• At any time
• Everywhere on earth (at least outdoors!)• How to navigate to the destination?
• Guidance or Navigation• How to synchronize time globally?
• Mobile phones• Financial Institutes

How far ?
Which Route ?

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

Slide : 3

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• Satellite-based Navigation or GNSS
• TRANSIT, GPS, GLONASS, GALILEO, QZSS,BEIDOU (COMPASS), IRNSS• Global, Difficult to Interfere or Jam, HighAccuracy & Reliability• Gyroscope, Accelerometer, Compass,
Odometer• Complicated, Errors accumulate quickly
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 4

What is GNSS?
Global Navigation Satellite System (GNSS) is the standard generic term for allnavigation satellites systems like GPS, GLONASS, GALILEO, BeiDou, QZSS, NAVIC.
• Global Constellation• Regional Constellation• GPS USA
• GLONASS, Russia• Galileo, Europe• BeiDou (COMPASS) / BDS, China• QZSS, Japan• NAVIC (IRNSS), India

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

Slide : 5

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)

PRN code numbers are given in the bracket

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

Slide : 6

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

Satellite Transmits Signal at 0ms.

Receiver Receives
the Same Signal
after 67ms.

25ms

0ms

50ms

Satellite with a known positiontransmit a regular time signal.

75ms

Speed of Light
300,000 km/s

25ms

50ms

Distance = (Transmission time – Reception time)× Speed of light
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 7

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(x0,y0,z0)k 

x  x   y  y   z  z   b
2

k

0

2

k

0

2

k

0

If k ≥ 4, solve for x, y, z and clock bias, b∆tCorrelation between Incoming Signal andReceiver Generated Signal

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

Slide : 8

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

• Used to identify satellite ID in CDMA
• Requires to modulate the data
• Should have good auto-correlation and cross-correlation properties• Navigation Data

• Includes satellite orbit related data (ephemeris data)• Includes satellite clock related information (clock errors etc)
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 9

GPS L1C/A Signal Structure
900 Phase Reversex154

L1 Carrier, 1575.42Mhz
Carrier Signal

X1, Clock10.23Mhz∑

x1/10

C / A Code, 1.023Mhz
PRN Code

L1 Band GPS Signal

x1/204600

Navigation Data, 50Hz
Navigation Data

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

Slide : 10

GNSS ArchitectureSpace Segment
GNSS Satellites

GPS
GPS

GPS

User Segment
GNSS Receivers
Applications that use GNSS

Control Segment
Monitor Satellite Health, Orbit, Clock etc
Upload Navigation Data to Satellites

GNSS
ReceiverMarine / AIS

Finance
SafetySecurity

Aviation / WAAS

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

Mobile Phone

ITS / ADAS
Slide : 11

GPS Space Segment: Current & Future Constellation
Legacy Satellites

Block IIA
0 operational
•
•
•
•
•

Coarse Acquisition (C/A)
code on L1 frequency forcivil users•
Precise P(Y) code on L1 •& L2 frequencies for•military users
7.5-year design lifespan •Launched in 1990-1997 •Last onedecommissioned in 2019

Modernized Satellites

Block IIR
9 operational

Block IIR(M)
7 operational••

C/A code on L1
P(Y) code on L1 & L2•
On-board clockmonitoring
7.5-year design lifespan •Launched in 1997-2004••

Source: http://www.gps.gov/systems/gps/space/#IIF
https://www.unoosa.org/oosa/en/ourwork/icg/annual-meetings

All legacy signals•
2nd civil signal on L2•(L2C)
New military M code•signals for enhanced jam•
resistanceFlexible power levels formilitary signals•
7.5-year design lifespan•Launched in 2005-2009

Block IIF
12 operational
All Block IIR-M signals
3rd civil signal on L5
frequency (L5)
Advanced atomic clocks
Improved accuracy,
signal strength, andquality
12-year design lifespanLaunched in 2010-2016

Information in this slide may not be the latest information.
Please check the Source HP link and UNOOSA documents

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

GPS III
2 operational
•
•
•
•
•
•
•

All Block IIF signals
4th civil signal on L1(L1C)
Enhanced signal
reliability, accuracy, andintegrity
No Selective Availability
15-year design lifespan
IIIF: laser reflectors;
search & rescue payload
First launch in 2018

Last update of the slide 2020/09/11

Slide : 12

GPS Signals
Band

L1

L2

L5

Frequency,
MHz1575.421227.60

1176.45

Modulation
Type

Data /
SymbolRate,
bps/sps

Notes

1.023

BPSK

50

Legacy Signal

10

1.023

BOC(1,1)

50 / 100

From 2014

CPilot

10

1.023

TMBOC

No Data

BOC(1,1) & BOC(6,1)P(Y)

7 days

10.23

BPSK

CM

20

0.5115CL

1500

0.5115

P(Y)

7days

10.23

I

1

Q

1

SignalType

CodeLengthmsec

Chip Rate,
MHz

C/A

1

CData

10.23

BPSK

Restricted

25 / 50
No DataModulated by TDM of(L2CM xor Data) andL2CL

50 / 100

Provides Higher
Accuracy

BPSK
BPSK

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

No DataSlide : 13

GLONASS (Russia)
1982 First Launch

2003

2011

Planned Launch

GLONASSGLONASS-M

GLONASS-K1

GLONASS-K2

DECOMMISSIONED
87 Launched
0 Operational
81 Retired
6 LostUnder Normal Operation
45 Launched
27 Operational
12 Retired
6 Lost•L1OF, L1SF
• L2SF•L1OF, L1SF
•L2OF, L2SF
•L3OC

Under Production /Operation
2 Launched
2 Operational
First launch Dec 2014

•L1OF, L1SF
•L2OF, L2SF
•L3OC

Information (Number of Satellites) in this slide are not updated
Please check the following site for the latest updates:
https://www.unoosa.org/oosa/en/ourwork/icg/annual-meetings.html

Under Development
3 On OrderFirst Launch Expected 2018

•L1OF, L1SF
•L2OF, L2SF
•L1OC, L1SC
•L2OC, L2SC
•L3OC

GLONASS space segment STATUS & MODERNIZATION, Joint - Stock Company «Academician M.F. Reshetnev» Information Satellite Systems»
ICG‐7, November 04‐09, 2012 , Beijing, China, https://en.wikipedia.org/wiki/GLONASS-K2
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 14

Galileo (Europe)

Information (number of satellites) in this slide are not updated
Please check the following site for the latest updates:
https://www.unoosa.org/oosa/en/ourwork/icg/annual-meetings.html
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 15

Galileo Signals
Band

E1

E6

E5
1191
.795
MHz

Frequency, MHz1575.421278.75

1176.451207.14

Modulation
Type

Data /
SymbolRate,
bps/sps

Notes

10.23

BOC(15,2.5)??

Restricted

4

1.023

CBOC, Weighted

125 / 250

Data

CPilot100

1.023

combination of
BOC(1,1) & BOC(6,1)

No Data

Pilot

A

10

5.115

BOC(15,5)

??

PRS

B

1

5.115

BPSK(5)

500 /
1000

Data

C

100

5.115

No Data

Pilot

A-I

20

10.23

25 / 50

Data

A-Q

100

10.23

No Data

Pilot

B-I

4

10.23

125 / 250

Data

No Data

Pilot

SignalType

CodeLength
msec

Chip
Rate,
MHz

A

10

BData

AltBOC(15,10)

B-QDinesh Manandhar,
100CSIS, The University
10.23
of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 16

Galileo Services
Open Service(OS)

Freely accessible service forpositioning, navigation and timing formass market

Commercial Service(CS)

Delivers authentication, high accuracy
and guaranteed services for commercial
applications

Public Regulated
Service (PRS)

Encrypted service designed for greaterrobustness in challenging environments

Search And Rescue
Service (SAR)

Locates distress beacons and confirmsthat message is received

Safety of Life Service(SoL)

The former Safety of Life service is being re-profiled

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

Slide : 17

BeiDou Space Segment

Information (number of satellites) in this slide are not updated
Please check the following site for the latest updates:
https://www.unoosa.org/documents/pdf/icg/2019/icg14/05.pdf
Source: Update on BeiDou Navigation Satellite System, Chengqi Ran, China Satellite Navigation OfficeTenth Meeting of ICG, NOV 2015
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 18

QZSS (Quasi-Zenith Satellite System)
Nickname: MICHIBIKI

Please check the document for the latest updates:
https://www.unoosa.org/documents/pdf/icg/2019/icg14/06.pdf

QZSS orbit is designed in such a way that a satellite is visible for about 8 hours above
your head. This makes the satellite visible even in very dense urban area with highrise buildings. GPS alone is not enough for good position accuracy in such area. QZSSin combination with other visible GNSS satellites provide better position accuracy.

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

Slide : 19

QZSS Constellation Plan

Equator1 sat constellation

4 sat. constellation

7 sat. constellation

Number of Satellites

QZO ●: 1

QZO ●: 3, GEO ●: 1

QZO●:4, GEO●:2, QGO●:1

PurposeResearch & Development

Operational

Operational,

Complements GPS for
positioning

Autonomous Positioning
Capability with QZSS only

Government Authority

JAXA

Cabinet OfficeCabinet Office

Operation

2010～（10 years）

2018～（15 years）

2023～（15 years）

Service Time / day (Japan)

8 hours / day

24 hours / day

24 hours / day

QZO: Quasi-zenith Orbit / GEO: Geosynchronous Orbit / QGO: Quasi-geostationary Orbit
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Source: MGA 2019, Mitsubishi
Slide : 20

Merits of QZSS• QZSS signal is designed in such a way that it isinteroperable with GPS• QZSS is visible near zenith; improves visibility &DOP in dense urban area
• Provides Orbit Data of other GNSS signals• Provides Augmentation Data for Sub-meter andCentimeter level position accuracy• Provides Messaging System during Disasters
http://qzss.go.jp/en/overview/services/sv04_pnt.html
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 21

QZSS PRN Codes
Satellite
QZS-1

QZS-2

QZS-3

QZS-4

SVN
J001

J002

J003

J004

Positioning Signals

PRN

L1C/A, L1C, L2C, L5

193

L1S

183

L6

193

L1C/A, L1C, L2C, L5

194

L1S

184

L5S

196

L6

194

L1C/A, L1C, L2C, L5

199

L1S

189

L5S

197

L1Sb

137

L6

199

Sr/Sf

-

L1C/A, L1C, L2C, L5

195

L1S

185

L5S

200

L6

195

Satellite

Launch Date (UTC)

Orbit (*1)

QZS-1

2010/9/11

QZO

QZS-2

2017/6/1

QZO

QZS-3

2017/8/19

GEO

QZS-4

2017/10/9

QZO

https://qzss.go.jp/en/technical/satellites/index.html#QZSS
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 22

NavIC Signal Types
SignalCarrierFrequency

Bandwidth

L51176.45MHz

24MHz

S

2492.028MHz

16.5MHz

Please check the following document for the latest information
https://www.unoosa.org/documents/pdf/icg/2019/icg14/01.pdf

See file 01_NAVIC_ICG_2019.pdf for the latest information as per DEC 2019

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

Slide : 23

NavIC (Navigation with Indian Constellation)• Consists of 7 Satellites• 4 Geo Synchronous Orbit (GSO) satellites• at 55oE and 111.75oE at an inclination of 27o• 3 Geo Stationary Satellites (GEO)• at 32.5oE, 83oE and 129.5o E at an inclination of 5o• Transmits signals in L5 band (1176.45MHz) and S
band (2492.028MHz)
Please check the following site for the latest updates:
https://www.unoosa.org/oosa/en/ourwork/icg/annual-meetings.html

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

Slide : 24

Multi-GNSS Signals
L5 / E5

L2

L6 / E6

L1 / E1

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

S

Slide : 25

JAKARTABANGKOK

MANILAKUALALUMPUR

Ho Chi MinhTOKYO

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

Slide : 26

Multi GNSS Signals: Benefits to Users• GPS+GLONASS+Galileo+BeiDou+QZSS+NAVIC• Asia-Oceanic region will see the maximum number of satellites

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

Slide : 27

Multi GNSS Signals: Benefits to Users• Increase in usable SVs, signals and frequencies• Increase in availability and coverage• More robust and reliable services• Higher accuracy in bad conditions• Less expensive high-end services• Better atmospheric correction• Emerging new and expanding existing applications are to be expected• Atmosphere related applications• Short Message Broadcasting• SAR (Search And Rescue Applications)• Signal Authentication and Secured Positioning Services• Bi-static Remote Sensing (GNSS Reflectometry)• Compute Soil Moisture, Wind Velocity, Sea Wave Height etc…

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

Slide : 28

Part - B

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

Slide : 29

Architecture of a GNSS Receiver
Antenna

LNA &Down Converter

Acquisition
To find out visible satellites,
approximate Doppler
and Code-phase

Tracking

To continuously demodulate thesignalto extract the navigation data bits
Done by using DLL, FLL and PLL.

Position Output(PVT)

Navigation

Generate Pseudorange, Doppler etc
Extract Ephemeris orSatellite Orbit related Data
Extract Clock related data

PVT Output
Position, Velocity and Time
Satellite Related Data
Signal Related Data

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

Slide : 30

GPS Signal Processing in a Receiver: Signal Demodulation

Incoming signal from satellite to a receiver

Replica signal generated in a receiver GPS receiver demodulates the incoming signal to extract navigation data and other signal related values that arenecessary to compute position of the receiver This is done by generating a replica signal (carrier and PRN code) that is similar to GPS incoming signal in the receiver All these process are done in steps called (1) Acquisition (2) Tracking (3) Navigation

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

Slide : 31

Architecture of a GNSS Receiver
GPS RF signal at1575.42MHz

Convert to
Lower Frequency
Defined by
Sampling Frequency and IF

For Example:
IF = 4.013 MHz
Fs = 16.3676 MHz

Antenna

Digital Signal Output
AGC

Pre-Amp(LNA)

Down Converter

A/D Converter

Oscillator
Ref. Clock 10.23MHz

Frequency
Generator

Output fromBase-band
Signal Processing

Replica Signal Generator
PRN Code + Carrier Signal

Baseband Signal
Processing

Acquisition

Tracking

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

Position Output(PVT)

To find out visible satellites,
approximate Doppler
and Code-phase
To continuously demodulate the signal
to extract the navigation data bits
Done by using DLL, FLL and PLL.
Outputs from Acquisition
are used as input for Tracking
Generate Pseudorange, Doppler etc
Extract Ephemeris orSatellite Orbit related Data
Extract Clock related data
Slide : 32

PRN (Pseudo Random Noise) Code• PRN Code is a sequence of randomly distributed zeros and ones that is one millisecondlong.
• This random distribution follows a specific code generation pattern called Gold Code.
• There are 1023 bits of combination of 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 is continually repeated every millisecond and serves for signal transit time measurement.
• The receiver can measure where the PRN code terminated or repeated. The start and end
points are known.
1ms / 1023

0 1 0 1 0 0 11 0 1 0 0
1ms
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 33

Acquisition of GPS L1C/A Signal
Correlate incoming signal with replica signal generated by the receiver∆t

Correlation between Incoming Signal andReceiver Generated Signal

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

Slide : 34

GPS Signal Tracking• Tracking Loops (PLL & DLL) are used to continuously lock theincoming signal and demodulate it by using the carrier
frequency and code phase values detected in Acquisition.
• PLL• Phase Lock Loop
• To Track the Carrier Frequency• DLL• Delay Lock Loop
• To Track the Code Phase (PRN Code Delays)
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 35

GPS Signal Tracking Output
Navigation Data Bits 1’s and 0’s
Now, we have all necessary outputs
1. Information necessary to compute Pseudorange and code phasefrom DLL Outputs
2. Information necessary to computer Doppler and carrier phasefrom PLL outputs
3. Navigation data bits from tracking output
1. It provides clock related information, satellite orbit
information (Ephemeris and Almanac), health status andmany other parameters.
4. Other signal properties like SNR

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

Slide : 36

Navigation Data
• Navigation Data or Message is acontinuous stream of digital datatransmitted at 50 bits per second.
• Each satellite broadcasts the following
information to users.

GPS Signal Demodulation
Incoming signal from satellite to receiver

Replica Signal in Receiver• Its own highly accurate orbit and clock
correction (ephemeris)• Approximate orbital correction for all othersatellites (almanac)• System health and other signal and satellite
related inforamtion
Demodulated Navigation Data Bits

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

Slide : 37

GPS L1C/A Signal NAV MSG

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

Slide : 38

GPS L1C/A, Navigation Message, Sub-frame 1

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

Slide : 39

GPS L1C/A Signal NAV MSG, Sub-frame 2

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

Slide : 40

GPS L1C/A Signal NAV MSG, Sub-frame 3

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

Slide : 41

GPS L1C/A Signal NAV MSG, Sub-frame 4 Page 1,6,11,16,21

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

Slide : 42

GPS L1C/A Signal NAV MSG, Sub-frame 4 Page 12,19,20,22,23,24

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

Slide : 43

GPS L1C/A Signal NAV MSG, Sub-frame 4, Page 14, 15

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

Slide : 44

GPS L1C/A Signal NAV MSG, Sub-frame 4, Page 17

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

Slide : 45

GPS L1C/A Signal NAV MSG, Sub-frame 5

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

Slide : 46

Part - C

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

Slide : 47

SBAS Message Format

Preamble
8 bitsData Rate
Symbol Rate

MessageType
6 bitsData
212 bits

CRC
24 bits: 250bps: 500sps (1/2 rate FEC)

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

Slide : 48

U-blox Screen Shot

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

Slide : 49

GNSS Navigation Data Bits

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

Slide : 50

QZSS Navigation Message Data BitsSV
QZSS 1QZSS 1QZSS 3QZSS 3QZSS 7QZSS 7MSG
L1S
0
L1C/A 0
L1S 0
L1C/A 0
L1S 0
L1C/A 0DATA (* denotes invalid words)
43
9AADF545 D18002C3 F25880CB 115A81F9 503FCA08 214106A8 64500013 7E7063B1
3
22C0AA24 2E8E83F8 3FD7D58F 2D517A6C 3FF28752 AA27838C 060F7023 0D26BAE0 3FF4A787 2E78F7AB
43
9AADF545 D18002C3 F25880CB 115A81F9 503FCA08 214106A8 64500013 7E7063B1
3
22C0AA81 AE8E8327 00263E35 BA997E7F 3FBF0777 03133174 3061EFC3 3F4A8413 3FFA2DF0 2E7DE57F
43
9AADF545 D18002C3 F25880CB 115A81F9 503FCA08 214106A8 64500013 7E7063B1
3
22C0AA81 AE8E8327 01D759E0 25981C5D 8069002C 036272D5 809D87FF 2ECDBB5E 80021FAB 2E40007C

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

Slide : 51

Earthquake Early Warning Message Format

https://qzss.go.jp/en/technical/ps-is-qzss/ps-is-qzss.html
https://qzss.go.jp/en/technical/ps-is-qzss/is_qzss_dcr_008_agree.html

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

Slide : 52

Earthquake Early Warning Message Format

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

Slide : 53

DC Report message output from a receiver• DC Report message output format• All output data shall be interpreted as ASCII characters• The beginning of the sentence is message header "$QZQSM“• Satellite ID is 6 LSB of the 8 bit which represented PRN of the L1S• PRN 183 0xB7 10110111b  110111b (Take 6LSBs)  5510
• PRN 183 corresponds to 55• 250bit DC Report Message are added two binary data "00" at end of amessage to make 252 bit data
• A carriage return code (CR) and a linefeed code (LF) are added at the end of asentence

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

Slide : 54

DC Report message output from a receiver

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

Slide : 55

Part - D

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

Slide : 56

Data Formats: NMEA, RINEX, RTCM

References: https://www.nmea.org/
http://freenmea.net/docs
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 57

National Marine Electronics Association (NMEA) Format• NMEA is format to output measurement data from a sensor in a
pre-defined format in ASCII• In the case of GPS, It outputs GPS position, velocity, time andsatellite related data
• NMEA sentences (output) begins with a “Talker ID” and“Message Description”• Example: $GPGGA,123519,4807.038,N,01131.000,E,1,08,0.9,545.4,M,46.9,M,,*47• “$GP” is Talker ID• “GGA” is Message Description to indicate for Position Data
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 58

NMEA Data Format

GGA - Fix data which provide 3D location and accuracy data.
$GPGGA,123519,4807.038,N,01131.000,E,1,08,0.9,545.4,M,46.9,M,,*47
Where: GGA Global Positioning System Fix Data
123519Fix taken at 12:35:19 UTC
4807.038, N
Latitude 48 deg 07.038' N
01131.000, E
Longitude 11 deg 31.000' E
1 Fix quality:
0 = invalid ,1 = GPS fix (SPS),
2 = DGPS fix,
3 = PPS fix,
4 = Real Time Kinematic
5 = Float RTK
6 = estimated (dead reckoning) (2.3 feature)
7 = Manual input mode
8 = Simulation mode
08
Number of satellites being tracked
0.9
Horizontal dilution of position
545.4,M
Altitude, Meters, above mean sea level
46.9,M
Height of geoid (mean sea level) above WGS84 ellipsoid(empty field)
time in seconds since last DGPS update (empty field) DGPS station ID number*47
the checksum data, always begins with *Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 59

RINEX Data Format• RINEX: Receiver Independent Exchange Format is a data exchange format for raw satellite data
among different types of receivers.
• Different types of receivers may output position and raw data in proprietary formats• For post-processing of data using DGPS or RTK it is necessary to use data from different types ofreceivers. A common data format is necessary for this purpose.
• Example: How to post process data from Trimble, Novatel and Septenrtio receivers to compute a
position?

• RINEX only provides Raw Data. It does not provide position output.
• User has to post-process RINEX data to compute position• Raw data consists of Pseudorage, Carrierphase, Doppler, SNR• RINEX basically consists of two data types• “*.*N” file for Satellite and Ephemeris Related data.
• Also called Navigation Data

• “*.*O” file for Signal Observation Data like Pseudorange, Carrier Phase, Doppler, SNR• Also called Observation Data

• The latest RINEX version is 3.04, 23 NOV 2018

• Note: Not all the software and receivers are yet compatible with the latest version• Make sure which version of RINEX works the best with your software
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 60

RINEX “N” File for GPS

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

Slide : 61

RINEX “O” File GPS, GLONASS, GALILEO, QZSS, SBAS

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

Slide : 62

RINEX “O” File, Continued from previous slide

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

Slide : 63

RTCM
• RTCM : Radio Technical Commission for Maritime Services• An internationally accepted data transmission standard for base-station data transmission
to a rover defined. The standards are defined and maintained by RTCM SC-104• RTCM SC-104 (Special Committee 104)
• Defines data formats for Differential GPS and• RTK (Real-Time Kinematic Operations)• The Current Version is RTCM-3 (10403.3)• Refer https://www.rtcm.org/ for detail information and document• Documents are not free
• A normal user does not need RTCM document.
• GNSS receivers with base-station capabilities will setup necessary messages for RTK• If you are developing a system or application you may need it

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

Slide : 64

Coordinate Systems

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

Slide : 65

Geodetic Coordinate System
Satellite

Pole
Semi Minor Axis

User at P (Latitude, Longitude, Height)

Ellipsoid Surface

Normal Vector to
Ellipsoid at Point P
Geodetic Latitude at P

Semi Major Axis

EquatorSemi Major Axis

Geodetic Longitude at P

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

Slide : 66

ECEF (Earth Centered, Earth Fixed)
ECEF Coordinate System is expressed by assuming the center of the earth coordinate as (0, 0, 0)

P (X, Y, Z)(0, 0, 0)
EquatorDinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 67

Coordinate Conversion fromECEF to Geodetic and vice versa
Geodetic Latitude, Longitude & Height to
ECEF (X, Y, Z)

ECEF (X, Y, Z) to
Geodetic Latitude, Longitude & Height𝑍+𝑒 2 𝑏 𝑠𝑖𝑛3 𝜃
𝜑=atan 𝑝−𝑒 2𝑎𝑐𝑜𝑠3𝜃

𝑋 = 𝑁 + ℎ cos 𝜑 cos 𝜆𝑌 = 𝑁 + ℎ cos 𝜑 sin 𝜆Z = 𝑁 1 − 𝑒 2 + ℎ sin 𝜑𝜆=atan2 𝑦, 𝑥
𝑃
ℎ=
−N 𝜑
cos 𝜑
𝑃=

𝜑 = 𝐿𝑎𝑡𝑖𝑡𝑢𝑑𝑒
𝜆 = 𝐿𝑜𝑛𝑔𝑖𝑡𝑢𝑑𝑒
h = Height above Ellipsoid𝑥2 + 𝑦2𝜃 = 𝑎𝑡𝑎𝑛𝑁 𝜑 =Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

𝑍𝑎
𝑃𝑏
𝑎

1−𝑒 2 𝑠𝑖𝑛2 𝜑

Slide : 68

Ellipsoid, Geoid and Mean Sea Level (MSL)
Mountain Peak
1

Ellipsoidal height (h)Mean Sea Level (MSL) Height, H
Geoid Height (N)
h

2

h

N

MSL Height, H

N

Land, Mountains, Valleys

Sea

Sea

MSL Height (H) = Ellipsoidal height (h) – Geoid height (N)Geoid Height is negative if its below Ellipsoidal height

Example at point (1) : h = 1200m, N = -30m
H = h – N = 1200 – (-30) = 1200 + 30 = 1230m

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

Example at point (2) : h = 300m, N = +15m
H = h – N = 300 – 15 = 285m

Slide : 69

Height Data Output in u-blox Receiver, NMEA Sentence, $GNGGA Sentence
MSL (Altitude)

Geoid Height (Separation between Geoid and Ellipsoid)$GNVTG,,T,,M,0.010,N,0.018,K,D*30$GNGGA,012039.00,3554.18235,N,13956.35867,E,2,12,0.48,54.4,M,39.6,M,0.0,0000*5D$GNGSA,A,3,03,04,06,09,17,19,22,28,194,195,02,,0.92,0.48,0.78,1*06$GNGSA,A,3,11,12,04,24,19,31,33,,,,,,0.92,0.48,0.78,3*00$GNGSA,A,3,30,01,03,14,08,28,33,04,02,07,10,13,0.92,0.48,0.78,4*08$GPGSV,5,1,17,01,18,076,,02,04,279,36,03,43,045,43,04,34,109,41,1*6C$GPGSV,5,2,17,06,38,295,43,09,26,152,40,11,02,107,29,17,74,330,47,1*67$GPGSV,5,3,17,19,53,320,45,22,22,048,39,28,36,213,43,41,18,249,39,1*6D$GPGSV,5,4,17,50,46,201,40,193,52,172,43,194,16,193,40,195,85,163,46,1*5E$GPGSV,5,5,17,199,46,201,37,1*66$GAGSV,2,1,07,04,25,175,40,11,28,299,37,12,65,007,43,19,50,105,40,7*72$GAGSV,2,2,07,24,27,245,41,31,09,198,36,33,33,082,42,7*43$GBGSV,4,1,15,01,48,172,43,02,19,248,36,03,39,225,43,04,44,148,42,1*7C$GBGSV,4,2,15,06,00,185,29,07,39,214,41,08,53,305,43,10,44,248,42,1*7C$GBGSV,4,3,15,13,33,283,42,14,23,043,38,27,55,323,48,28,61,092,48,1*71$GBGSV,4,4,15,30,05,306,36,32,17,206,42,33,48,055,46,1*4F$GNGLL,3554.18235,N,13956.35867,E,012039.00,A,D*76

The NMEA sentences in this figure are from u-blox receiver.
NMEA format uses “Mean Sea Level” for height data (shown in blue texts).
Also it provides Geoid Height (Geoid Separation) value.
GPS by default is Ellipsoidal height and this height is converted to Mean Sea Level heightusing the geoid Height (shown in red texts) .
This means, u-blox receiver uses a built-in database of Geoid Height.
U-blox also outputs Ellipsoidal height in proprietary message $PUBX,00 (marked as altRef)$PUBX,00,time,lat,NS,long,EW,altRef,navStat,hAcc,vAcc,SOG,COG,vVel,diffAge,HDOP,VDO
P,TDOP,numSvs,reserved,DR,*cs<CR><LF>
altRef  Altitude above user datum ellipsoid

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

Slide : 70

Geodetic Datum: Geometric Earth Model
GPS uses WGS-84 Datum

Semi-Minor Axis

Pole

Semi-Major Axis

EquatorBut, topographic maps and many other maps use different
datum. Before using GPS data on these maps, its necessary
to convert GPS coordinates from WGS-84 to local
coordinate system and datum. Many GPS software havethis tool. Also, GPS receivers have built-in datum selection
capabilities.
Check your receiver settings before using.

WGS-84 Geodetic Datum Ellipsoidal Parameters
Semi-Minor Axis, b = 6356752.3142m
Semi-Major Axis, a = 6378137.0m
Flattening, f = (a-b)/a= 1/298.257223563
First Eccentricity Square = e^2 = 2f-f^2= 0.00669437999013
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 71

Points to Be Careful in GPS Survey• Datum• Which Datum is used for GPS Survey?
• By default, GPS uses WGS-84• But, your Map may be using different datum like Everest• Make Sure that Your Map and Your Coordinates from the GPS are in the same Datum, if
not, datum conversion is necessary• You can get necessary transformation parameters from your country’s survey
department• Height• Which Height is used?
• By default GPS uses Ellipsoidal Height• But, your Map may be using Mean Sea Level (MSL or Topographic) Height• You need to convert from Ellipsoidal Height into MSL Height• Use Ellipsoidal and Geoid height Difference Data for your survey region• You can get it from your country’s survey officeDinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 72

GNSS Errors

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

Slide : 73

Background Information: Accuracy vs. Precision• Accuracy• Capable of providing a correct measurement• Measurement is compared with true value• Affected by systematic error• Precision• Capable of providing repeatable and reliable measurement• Statistical analysis of measurement provides the precision• Measure of random error• Systematic error has no effect

Neither Precise nor Accurate Precise but Not Accurate

Accurate but Not Precise

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

Precise and Accurate
74

Slide : 74

GNSS Measurement Errors
MeasureAbbreviation

Definition

Root Mean SquareRMS

The square root of the average of the squared errors

Twice Distance RMS

2D RMS

Twice the RMS of the horizontal errors

Circular Error Probable

CEP

A circle's radius, centered at the true antenna position,
containing 50% of the points in the horizontal scatter plot

Horizontal 95%
Accuracy

R95

A circle's radius, centered at the true antenna position,
containing 95% of the points in the horizontal scatter plot

SEP

A sphere’s radius centered at the true antenna position,
containing 50% of the points in the three dimensional scatter
plot

Spherical Error Probable

Source: GPS Accuracy: Lies, Damn Lies, and Statistics, GPS World, JAN 1998
https://www.gpsworld.com/gps-accuracy-lies-damn-lies-and-statistics/
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 75

Commonly Used GNSS Performance Measurements• TTFF• True Time to First Fix• Parameter: Cold Start, Warm Start, Hot Start• Standard Accuracy• Accuracy attainable without any correction techniques• DGPS Accuracy• Accuracy attainable by differential correction data
• Code-phase correction• RTK Accuracy• Accuracy attainable by differential correction data
• Use both Code-Phase and Carrier Phase correction
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 76

TTFF and Typical Example Values• TTFF• Cold Start : < 36 seconds• Time required to output first position data since the receiver power is on• No reference data like time or almanac are available• Warm Start : < 6 seconds• Time required to output first position data since the receiver power is onwith the latest satellite almanac data in the receiver’s memory• Time and almanac related reference data are already known• Hot Start : < 1 second• Receiver has already output position data
• Time to reacquire an already tracked satellite due to temporary blockage
by buildings or trees
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 77

Performance Measurement of RTK Accuracy• A fix error and a variable error with respect to base-length is given• Such as : x cm + y ppm• Example: 2cm + 1ppm

• There is a fix error of 2cm plus 1ppm error due to base-length between the Base and Rover• 1ppm  1 parts per million•  1cm of error in 1 million centimeter distance between the Base and the Rover•  1cm of error in 1000000 centimeter distance between the Base and the Rover•  1cm of error in 10000 meter distance between the Base and the Rover•  1cm of error in 10 kilometer distance between the Base and the Rover•  1cm of error for every 10Km of distance between the Base and the Rover•  4cm of error for 40Km of distance between the Base and the Rover• Thus the total error is : 2cm + 4cm due to 40Km of base length• The longer the base-length, the larger the error• Do not assume that this error is linear• And it may not be valid for longer base-lines• Normally the recommended base-length for RTK for a Geodetic Receiver is 40Km
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 78

Part - E

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

Slide : 79

GNSS Applications

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

Slide : 80

GNSS Applications - 1• Surveying, Mapping and Geodesy• Transportation• Car Navigation, ITS, ADAS, V2X• Railway Network• Marine : AIS, VMS• Aviation : SBAS / GBAS• UAV / DRONE• 3-D Mapping without GCP• Vehicle Accidents / Emergency Services• eCall/ ERA-GLONASS / E-911• Taxation / Insurance• Taxation based on location or distance traveled

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

Slide : 81

GNSS Applications - 2• Legal and Law Enforcement• Fishing Zone Management, Illegal Fishing Control• Crime Prevention• Agriculture– Precise farming, Auto or Semi-Auto Driving of Tractors– Product Supply-Chain Management• Location Based Applications– Services, Entertainment, Advertisement, Gaming, Marketing• Warning during Disasters•

EWS of QZSS, SAR of GALILEO• Geo-Fencing / Geo-Securities• Robotics•

Navigation, Actions based on Location• Scientific Applications•

Space Weather : Scintillation, Radio Occultation, Plasma Bubble
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 82

GNSS Applications - 3• Telecommunication• Synchronize cell towers, microsecond order for CDMA
• Network Time Protocol , millisecond order• Power Grid
• Phase Synchronization between grids is required for higher efficiency and avoid power failures• Time Stamping of• Financial and Banking Transactions• Legal, Clerical, Shipping Documents• Scientific Timing Applications• Time stamping of events• e. g. Global VLBI Observation, earthquake occurrences, arrival of neutrino in particle physics

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

Slide : 83

Abbreviations• ASAL – Algerian Space Agency• AUS-NZ – Geoscience Australia/New Zealand System• BDSBAS – BeiDou Satellite-Based Augmentation System• EGNOS – European Geostationary Navigation Overlay Service• GAGAN – GPS-Aided Geo-Augmented Navigation• GBAS – Ground-Based Augmentation System• KASS – Korean Augmentation Satellite System• MSAS – MTSAT Space-Based Augmentation System• NSAS – Nigerian Satellite Augmentation System• PRN – Pseudorandom Noise• QZSS – Quazi-Zenith Satellite System• SDCM – System of Differential Correction and Monitoring• WAAS – Wide Area Augmentation System

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

Slide : 84

Contact and Additional Information• Homepage• Main Page
• Webinar Page

: https://home.csis.u-tokyo.ac.jp/~dinesh/: https://home.csis.u-tokyo.ac.jp/~dinesh/WEBINAR.htm
https://gnss.peatix.com/• Training Data etc. : https://home.csis.u-tokyo.ac.jp/~dinesh/GNSS_Train.htm• Low-Cost Receiver : https://home.csis.u-tokyo.ac.jp/~dinesh/LCHAR.htm• Facebook: https://www.facebook.com/gnss.lab/• Contact• E-mail• Skype: dinesh@csis.u-tokyo.ac.jp: mobilemap

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

Slide : 85