MADOCA PPP Introduction
Yize Zhangzhyize@163.com
Tokyo University of Marine Science and Technology

01

GNSS and QZSS02

G N S S P o s i t i o n i n g Te c h n i q u e s

03

MADOCA PPPGNSS and QZSSWhat is GNSS?
•GNSS is a constellation of satellites
providing signals from space that transmit
positioning and timing data to GNSS
receivers.

•GNSS can provide positioning, navigation,and timing (PNT) service for users on theground and space..

https://www.spirent.com/blogs/positioning/2017/january/what-does-2017-hold-for-gnss

GNSS in earthquake monitoring
GNSS can also aplied in many other areas suchas earthquake monitoring, atmospheremonitoring, message communication.

https://www.nature.com/articles/s41586-020-2212-1

GNSS systems

GPSGALILEOIRNSSUSEUIndia

GLONASS

BeiDouQZSSRussiaChinaJapan

GNSS visibility at Tokyo

https://www.gnssplanning.com

GNSS segments

https://www.tersus-gnss.com/technology

QZSS
QZSS is a Japanese satellite positioning system composed
mainly of satellites in quasi-zenith orbits (QZO).
QZSS has been operated as a four-satellite constellationfrom November 2018, and at least three satellites arevisible at all times from locations in the Asia-Oceania
region. QZSS can be used in an integrated way withother GNSS systems.

http://qzss.go.jp/en/

QZSS visibility at Tokyo

https://app.qzss.go.jp/GNSSView/gnssview.html

QZSS development
Satellite

PRN

BLOCK

Type

Longitude

Launch

QZS-1

J01

IQ

IGSO

130~140°E

2010.09.11

QZS-2

J02

IIQ

IGSO

130~140°E

2017.06.01

QZS-3

J07

IIG

GEO

126.9~127.1°E

2017.08.19

QZS-4

J03

IIQ

IGSO

130~140°E

2017.10.09

http://qzss.go.jp/en/

QZSS signals and services
Frequency

SignalService1575.42MHz

L1C/A

PNT

L1C

PNT

L1S

Sub-meter Level Augmentation Service(SLAS)
Satellite Report for Disaster and Crisis Management (DC Report)

L1SbSBAS

1227.60MHz

L2C

PNT

1176.45MHz

L5PNT

L5S

Positioning Technology Verification Service

L6D

Centimeter Level Augmentation Service (CLAS)

L6E

Multi-GNSS Advanced Demonstration tool for Orbit and Clock
Analysis (MADOCA)

1278.75MHz

http://qzss.go.jp/en/

Benefit of QZSS
(1) Increase visible satellite number; high elevation
at most East-Asia countries, with small multipath
errors in urban environment.

(2) QZSS transmit different types of augmentation
data (SLAS, CLAS, MADOCA), enable different
level of positioning service.

GNSS Positioning Techniques

GNSS Positioning Techniques
SPP (Single Point Positioning)

Point Positioning
PPP (Precise Point Positioning)

DGNSS (Differential GNSS)
Relative Positioning
RTK (Real Time Kinematic)

GNSS Observation and Errors

SPP• SPP: With code observation(pseudo-range) from atleast 4 satellites, we can know the receiver
positioning from by Least Square or Kalman Filter.
jIPfj = ρ j + c δt f − c δt fj −  jrela + T j − 2 + ε Pff

Pseudo-range
observation

Ionospheredelay

Geometric distancefrom satellite toreceiver(X, Y, Z)

Troposphere Noise andother modeled
delay
Relativity
corrections
Receiver clock
correction
Satellite clockFrom SPP to PPP
SPP

PPP

Observables

Code(30cm)

Code (30cm)+Carrier
phase (3mm)

Satellite
ephemeris

Broadcast ephemeris(0.5~2m)

Precise ephemeris(1cm~10cm)

Error
correction

Ionosphere,troposphere, relativity

Ionosphere, troposphere,
relativity, instrument
delay (DCB), phasewindup, tidal correctionPositioningaccuracy

1~10m(Kinematic)

1~2cm(Static),5~20cm(Kinematic)

Why we can get high accuracy from PPP?
✓1 Carrier phase observation is used
✓2 Precise ephemeris (orbit and clock) is used
✓3 All errors are considered✓4 All inaccurate errors are estimatedAccuracy of different ephemeris

http://www.igs.org/products

SPP vs. PPP
SPPPPPDGNSSFor two stations within a few kilometers,
the errors from satellite andatmosphere, is at the similar level.

By setting up a base station, we can use
the “station differencing” strategy toremove the common errors.
Similar as SPP, DGNSS is based on codeobservation.

SPP vs. DGNSSSPPDGNSS

STD improve from [0.62,0.62,1.95]m to [0.22,0.23, 0.97]m

RTK
Similar as DGNSS, RTK also needs a basestation to eliminate most errors.
What is more, carrier phase observation isalso used.
Compared with PPP, RTK can fix theambiguity within short time(e.g. several
seconds), thus provides 1~3cm positioning
solution accuracy instantaneously.

Why we can get high accuracy from RTK?
✓1 Carrier phase observation is used
✓2 Errors from satellite and atmosphere are eliminated✓3 Ambiguity can be fixed

DGNSS vs. RTKDGNSS

RTKMADOCA PPPReal-time PPP• For post-processing PPP, we can use IGS or JAXA precise orbit
and clock file;• For real-time PPP, we can use State Space Representation(SSR) correction with broadcast ephemeris.
• In real-time PPP, the residual part satellite orbit and clockerror in broadcast ephemeris is corrected by SSR message(BRDC+SSR), making the accuracy of orbit and clock within
10 cm.
• For other error correction and parameter estimation, it issame as the post-processed PPP.

SSR and OSR (Observation Space Representation )• OSR describes lump sum of GNSS errors. Example: network
RTK(VRS, MAC, FKP);• SSR describes each individual GNS error. Example: PPP.
• Benefit of SSR:
✓SSR requires low bandwidth for large areas;✓Unlimited number of users and costs;✓Different service with different accuracy;✓Single/dual/triple frequency application;✓Independent of GNSS(troposphere and ionosphere).

SSR message

What is MADOCA?
✓MADOCA(Multi-GNSS
Advanced Demonstration
tool for Orbit and ClockAnalysis) is developed by
JAXA/GPAS.
✓MADOCA provides
GPS/GLONASS/QZSS orbit
and clock SSR corrections
through QZSS or internet inreal-time.

https://www.gpas.co.jp/en/service_madoca.php

MADOCA products

MADOCA products accuracy✓Goal of orbit/clock accuracy:✓Actual accuracy:

dx.doi.org/10.3390/s19112580

MADOCA products✓1 Real-time message from QZSS L6E signal (signal decoding,only areas where QZSS is visible)✓2 Real-time message from Ntrip (User account required, global,internet required)✓3 Offline RTCM3 SSR file from FTP (For post-processing)Real-time MADOCA PPP from QZSS L6E signal• The MSJ(Magellan System Japan)
receiver can provide high precision
positioning by using L6 signal fromQZSS.

Real-time MADOCA PPP from Ntrip• RTKLIB• GPASLIB• MAD-PI; MAD-WIN; MADDRIOD（Webinar 3）

Monitoring of MADOCA performance• We are monitoring theperformance of MADOCA
PPP in some Asian andOceanian countries.

Thank you!