A Novel Real-Time Precise Positioning Service System:
Global Precise Positioning With
Regional Augmentation
Maorong Ge(maor@gfz-potsdam.de), Xingxing Li, Jan Dousa,
Hongzheng Cui, Gerd Gendt, Jens Wickert
Junping Chen(SHAO), Xuan Zou(WHU)
German Research Centre for Geosciences
CSNC2011, Shanghai, China , 18-20 May 2011
Real-Time Positioning Services
Network Real-Time Kinematic (NRTK)
– Using a local/regional reference network
– OBS. DOMAIN Representation
NRTK Service Covers The Whole Chinese Territory?
Global Precise Point Positioning Service
– Using a global reference network
– STATE DOMAIN Representation
Initialization/Re-initialization takes 10-30 Min..
Global PPP + Regional Augmentation For All
Real-Time Applications
Contents
EPOS-RT Software
Global RT-PPP Service
Regional Augmentation
The Novel System
EPOS-RT Software
– Motivation
– Structure
– Progress
EPOS-RT: Motivation
Requirement of:
New IGS Products
 Multi-System, Multi-Technologies
 LEOs, GEOs, Huge Networks
IGS Real-Time Pilot Project
GFZ Ongoing Projects
Decision:
Multi-Technology: GNSS SLR VLBI …
Multi-Function: Real-time/Post-mission;
Static/Kinematic/Dynamic
EPOS-RT: Structure

Left Side: Post-Processing. Right Side: Real-Time
EPOS-RT: Progress
Since Sept. 2007
Already Available
– GPS/GLONASS Real-Time Clock Estimation
– GPS/GLONASS/LEO POD (Cui et al, EGU2011,
Presentation)
– Regional Augmentation/NRTK (Li et al, EGU2011, Poster)
– Real-Time ZTD (Bender et al, EGU2011, Presentation)
– Embeddable User Software
Further Coming
– GALILEO/COMPASS
– SLR
– IONO. Model
GFZ Global RT-PPP Service
– Hardware
– Software
– IGS Real-Time Analysis Centre At GFZ
– New Development in PPP
• PPP Ambiguity Resolution
• Data Gap Connection
Real-Time PPP Service (Hardware)
Geostationary
Satellite
GNSS-satellites
Correction data stream
INTERNET
Caster
User terminal with
GNSS receiver and
communication unit
and PPP software
GNSS reference
stations
EPOS-RT
Generation of correction
information
Orbit, clock, iono. UPD
Internet connection
GNSS observations
EPOS-RT For Real-Time PPP Service
IGS Real-Time Analysis Center at GFZ
RT Orbit
Hourly
BNC
RT ORB
BNC2SRIF
SRIF(Clk)
RT Clock
NTRIP Products
SRIF2BNS
GPS receivers
RT PPP
NTRIP Products
ORB/CLK/UPD
BNC2SRIF
SRIF(PPP)
Pos&Time
ZTD/STD
Control Unit
Internet connection
OBS Streaming
SRIF(Orb)
Control Unit
D
a
t
a
IGS Hourly Data
Standard PPP Server
Standard PPP Client
GFZ Real-Time Clock (Valid)
IGS RT PPP Online Validation:
http://igs.bkg.bund.de/ntrip/ppp
New Development in PPP
 PPP Ambiguity Fixing
To Shorten Convergence & To Improve
Position Accuracy
Uncalibrated Phase Delay (UPD)
 Data Gap Handling
To Avoid Re-Initialization
Temporal Stability of Atmo. Delays
UPD Generation For PPPAMB
UPD Generation For PPPAMB
PPP+AMBFIX:
1-2 cm in Horizontal, 3-4 cm in Vertical.
Initialization Time 15-20 Min.
Impact Summary
Long (Re)Convergence
Integer Ambiguity Fixing
Data Gap Handling
Integer Ambiguity Fixing
Expected NRTK Performance
Regional Augmentation
– System Configuration
– Bias Representation Using
UnDifferenced Obs. Corrections
– Realization of UD-Corrections
– Experimental Validation
Principal: Unambiguous OMC
OMC of Station k to Satellite i
omc
i
k
i
~
 L  k
 S k Orbit Bias
i
i
k
i
 S  t  tk  I
i
k
fk
 T  n  f k  f
i
f
i
k
i
k
i
k
i
UPD Receiver
UPD Satellite
Unambiguous OMC (Ambiguity Known)
l  omc  n
i
k
i
k
i
k
 S  t  tk  I  T  f k  f
i
k
i
i
k
i
k
i
Principal: Unambiguous OMC
Interpolated User Correction
lu 
i
  k ( S k   I k   T k )
i
i
Cor. Obs. Equ.
User Obs. Equ.
Interpolated
Correction
3
i
l u   S u   I u   Tu

0

Contant
 t  f  nu

nu
 u uxu

u uxu
i
i
i
i
k 1
3


k 1
i
k
( t k   f k )
 t  f
i
With  1   2   3  1
 tu  f u
i
i
i
i
i
i
Corrected Obs. Equ == PPP With Integer
SD-Ambiguities
How To Get The Integer UD-Ambiguities
For L1&L2 ?
Integer UD Ambiguities
“Consistent” Int. UD Amb. Instead of The True
Consistent == "Int. DD Amb. Constrained”
Two Ways (Ambiguity Mapping):
Without Precise Sat. Clocks --- New NRTK
(Based On Fixed DD-ambiguities)
With Precise Sat. Clocks--- PPP Augmentation,
(Based On Fixed UD/SD-ambiguities)
Network Solution Not A MUST
There is no limitation on the Number of Reference
Stations
Generation Of Augmentation Info.
PPP+Regional Augmentation Client
New NRTK: Data Processing
Data from Regional
Reference Network
BRD- (or Ultra
Rapid) Orbits
& Clocks
Data Processing
for Ambiguityfixing (Baseline
Mode)
Orbits & Clocks,
UPDs from Global
RTPPP Service
Data Processing
for Ambiguityfixing (PPP
Mode)
Fixed DD-ambiguities
OMC wrt Orbits & Clocks
PPP
+AMBFIX
RECEIVER
Ambiguity
Mapping
Computation of
Unambiguous OMCs
CASTER
With Reg. Info.
Accuracy: < 2cm
Initialization:
DF < 2min
SF < 10min
Validation SAPOS: Simulated RT
 DATA (Map: www.sapos.de)
 SAPOS Data of 290 stations
 Various receiver types
 30 seconds sampling rate
 Reference Network
 Selected 22 reference stations
 Inter-station distance 184 km
 Others are user stations
 Software
 EPOS-RT
Results: Fixing Time (Lw+L1)
 Lw+L1 can be fixed with 1 epoch data, On average
1.6 epochs, half of Lw (3 epochs)
 LW+L1+ION.PAR can furthermore reduce the fixing
time but slightly. Improvement found for cases where
long fixing time needed.
Results: Position Accuracy
Accuracy of the Positions at the first fixed epoch
Using Lw+L1
 Lw+L1 8, 6 and 21 mm in ENU, the same as L1 7,
6, and 20 mm
 Lw+L1+ION, slightly worse than Lw+L1, but fixing is
improved
Validation (CORS): Real Time
A Regional CORS Net
Network
 DATA
 A Regional CORS Network.
with 70 stations
 Stream Data of 1Hz
 Reference Network
 Selected 13 reference stations
Inter-station distance 150 km
 User stations
 Software
 Newly Developed at GFZ in
C++
Validation: Real-Time Results
 Every Minute Reset Filter
 90% Fixed With 1 Epoch, On
average 3 s
 Lw, 18, 14 and 34 mm ENU
 Lw+L1 in development
Summary of Augmentation
 UD-OMC Based On “Integer UD Ambiguity”
 Casted Station-By-Station
 Instantaneous Ambiguity Fixing Achievable
 Network Solution Not A MUST
 Augmented PPP To Replace NRTK
Global PPP With Regional
Augmentation
– System Configuration
– Regional Augmentation
– PPP Clients
Augmentation of PPP Service
Standard PPP Services
Global Ref.
Network
CLOCK
ORBIT
Without Reg. Info.
Accuracy:
• DF < 10 cm
• SF < 40 cm
Initialization:
< 20 min
Global Info
ORBIT, CLOCK IONOS
CASTER
IONOS
PPP
+AMBFIX
Regional Ref.
Network
Obs.Resid
uals/OMC
CASTER
Regional Info
With Reg. Info.
Accuracy: < 2cm
Initialization:
DF < 2min
SF < 10min
Obs. corrections
Regional Augmentation / Network RTK
Global Real-Time Precise Point Positioning
With Regional Augmentation
Generation Of Augmentation Info.
PPP Clients
Performance Of The Augmented
PPP Service
– Without Regional Augmentation
• Open Ocean, …
• 5-10 cm, after 30 min., 3-5 cm after
Ambiguity-Fixing (15 min)
– With Regional Augmentation
• Developed Cities, …
• 1-2 cm, within 1-2 min. depends on …
– Also For Single-Frequency And
Low-Cost Receivers
Further Work
As New Activity Under IGS-RTPP,
EUREF
Operational Test For China With
About 800 Reference Stations.
Operational Test As For Europe.