south african network of continuously operating gnss base ... · the south african network of...
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TrigNet: The South African Network
of Continuously Operating GNSS
Base Stations
ESESA User Need Workshop
Thread 2: Status of Current GNSS Applications in South Africa
Somerset West
2 March 2011
Base StationsR Wonnacott
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• General Considerations
• TrigNet Architecture
• Post Processing and Real Time Services
• Methods of Delivery
Overview
• Co-ordinate System
• Current Status
• Non-positioning Applications
• Future
• Conclusion
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• System must be receiver independent - RINEX, RTCM
• System must be reliable through integrity monitorin g and redundancy
• Post processing data must be as fresh as possible
General Considerations
• Real time services must be available as close to 24 /7 as possible
• Cost of services must not be excessive to user
• System must be expandable and flexible
• System must meet the accuracy demands placed on it
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• One control station at Mowbray
• Redundancy built into network
• Provide a range of post -processing services and
Basic Design 1
• Provide a range of post -processing services and products and real time services
• Have 58 stations in full operation and in process o f expanding (February 2011)
• Stations between 40 km and 300 km apart
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Post processing
or
Real time users
Remote station Remote station
Basic Design 2
Internet
Control centre
Remote station
Remote station
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SIGNAL SPLITTER
Remote Station Layout
GPS 2GPS 1
SWITCH / HUB
ROUTER
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• Data available in Receiver Independent Exchange for mat (RINEX V2.11 which includes L2C & L5 and other feat ures ).
• Hourly data from all stations available approximate ly 30 minutes after each hour of observation. - Unchecked
Post Processing Products 1
• 24 hour data available on following day from all st ations. Checked
• Data is available via internet (ftp) , e-mail, CD, DVD etc.
• Achievable accuracy could be 0.05 m or better depen ding on users receiver and antenna type, location, proce ssing software, etc
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Standard RINEX products
• 1 hour 1 second L1, L2 data• 24 hour 5 second L1 data• 24 hour 1 second L1,L2 data
Post Processing Products 2
• 24 hour 30 second L1,L2 data
Customized RINEX products• Wide range of options available through “RINEX Shop ” on
web page
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• Data available in Radio Technical Commission: Marit ime format (RTCM)
• DGPS– pseudo range corrections provided in RTCM V 2.3– sub metre accuracy possible from single base statio n
�RMS 0.35 m Hor and 1 m Vert irrespective of distance
Real Time Services
�RMS 0.35 m Hor and 1 m Vert irrespective of distance– used for navigation and GIS applications– Country wide coverage
• RTK– carrier phase corrections provided in RTCM V 3.1– sub 5 cm accuracy possible from 40km of a single b ase
station but generally�2-3 cm Hor and ~ 10cm Vert
– used for precise navigation and by surveyors and en gineers
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NTRIP (Network Transport of RTCM by Internet Protoc ol)
• Users download RTCM RTK observables or DGPS correc tions from an Internet site in real time.
• Corrections or GPS observables received are based e ither on one station or on a network solution.
Delivery of RT Services 1
one station or on a network solution.
• Field connection to internet can be via any technol ogy eg GSM, GPRS (3G), Satellite phone etc
• GSM & GPRS have disadvantages of coverage.
• Low cost GPRS costs ~R2/Mb. NTRIP uses ~400 Kb/hou r
• Could be used for in-shore hydrographic work or navi gation
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Delivery of RT Services 2
NTRIP Web Server-DGPS-RTK
GSM / GPRS
Network Control Centre
GSM / GPRSLand Line
etcRINEX Web Server
Base Station / User Seperation : Post processing – Po ssible to get <5cm @ 500km or greaterDGPS – 35cm irrespective of distance RTK – <5cm @ ~40 km
Active GNSS Base station
Real Time Users
Post Processing Users
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• GNSS and TrigNet are observing or measurement tools which operate in a co-ordinate reference frame different to Hartebeesthoek 94
• Users must transform surveys conducted using GNSS o r TrigNet to the official Hartebeesthoek 94 co -
Co-ordinate System 1
TrigNet to the official Hartebeesthoek 94 co -ordinate system.
X
Y
Yo
Xo
θ
y
x
GNSS / TrigNet ( ITRF 2005 )
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Differences between:
TrigNet
(ITRF 2005 epoch 2010.02)
and
Short nameITRF2005-Hart94
dy dx
ANTH -0.077 -0.426
BENI -0.265 -0.386
BETH -0.180 -0.417
BFTN -0.039 -0.387
Co-ordinate System 2
and
Hart94
(ITRF 1991 epoch 1994.0)
(NB Gauss Conform Lo co-ordinates)
BFTN -0.039 -0.387
BRIT -0.236 -0.387
BRNK -0.241 -0.343
BWES -0.140 -0.462
CALV -0.248 -0.475etc " "
etc " "
etc " "
Mean -0.197 -0.413
Stdev 0.073 0.056
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Simple view of plate motions
Co-ordinate System 3
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Hartebeesthoek 94 remains the official co -ordinate reference frame
Co-ordinate System 4
official co -ordinate reference frame for South Africa
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Status 2011-02-16
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Post processing applications• Surveying and GIS
• Atmospheric science•Monitoring of atmospheric water vapour for climate monitoring•Monitoring of ionosphere for communication and posi tioning
• Geophysics
Applications of TrigNet
• Geophysics•Long term monitoring of station positions – plate te ctonics
Real time applications• Surveying and GIS
• Navigation
• Weather forecasting & ionosphere mapping
• Timing
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Plate Motions within South Africa
Non-Navigation Applications 1
How rigid is a rigid plate?Geodetic constraint from the TrigNet CGPS network, South Africa.R. Malse r v i s i , U . H u g e n t o b l e r , R . W o n n a c o t t , R . C h a c k o IAESPEI Cape Town 2009
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Space weather
• Ionospheric mapping of variation of annual TEC over South Africa from network of GNSS base stations
Nov
Dec
Month
Nov
Dec
Month
Non-Navigation Applications 2
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Hour of day [UT]0 2 4 6 8 10 12 14 16 18 20 22 24
Hour of day [UT]0 2 4 6 8 10 12 14 16 18 20 22 24
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Thanks to B Opperman of Hermanus Magnetic Observatory for plots
2002 2004
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Climate monitoring and Weather forecasting
• Comparison of GNSS with Radiosonde estimates of Precipitable Water Vapour (PWV)
• Less than 3 hour latency required for weather forec asting
Non-Navigation Applications 3
0
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PW
V m
m
Comparison Radiosonde (IWV) / GPS (PWV)Bethelehem 1 - 31 March 2004
Mean diff (IWV-PWV) = -3.70 mmStd dev = 1.56 mm
GPS
RAOBs
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TrigNet data being used for:
• International GNSS Service (IGS) Real Time Working Group
• International GLONASS Service (IGLOS)
• Constellation Observing System for Meteorology, Ion osphere & Climate (COSMIC) and FORMOSAT-3 Taiwan's Formosa Satellite Mission #3
International Activities
•National Oceanic and Atmospheric Adminstration (Met erology)
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• Densification along Southern Cape Coast, Northern F ree State, KwaZulu-Natal and Central Cape with link to SKA
• Increase number of GPS/GLONASS receivers
Operationalize ionospheric mapping in co -operation with
Future
• Operationalize ionospheric mapping in co -operation with HMO Implications on single frequency positioning
• Increase co-operation with SAWS for weather forecas ting and climate monitoring applications
• Will have to consider a rebuild from about 2012 to cater for GPS modernization plus GLONASS and Galileo (2013???)
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• The services available from TrigNet are easily avai lable.
• NTRIP is “state of the art” in real time service pr ovision.
• The applications of TrigNet are not confined to positioning.
Conclusion
positioning.
• A rebuild is planned to accommodate GPS modernization, GLONASS and Galileo.
•TrigNet is building up a strong recognition within the International community as a provider of reliable a nd good quality data
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Thank You
Website for further information and data
www.trignet.co.za
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Plate Motions within South Africa
Non-Navigation Applications 1
C.J.H. Hartnady, E. Calais & R. Wonnacott (2007): “ ITRF2000 velocity field from the South African TrigNet GPS array and the African GNS S network: Implications for Nubia-(Rovuma-Lwandle-)Somalia plate motions” East Africa n Rift Conference, Kampala
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Remote Station
Remote Station
VRS - Networked Real Time Solution 2
Network Control Centre
Remote Station
Remote Station
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WWWNTRIP
Remote Station
Remote Station
VRS - Networked Real Time Solution 3
Network Control Centre
Remote Station
Remote Station
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WWWNTRIP
Remote Station
Remote Station
Virtual Reference
VRS - Networked Real Time Solution 4
Network Control Centre
Remote Station
Remote Station
New VRS computed when user 5 km from initial station
Reference Station (VRS)
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Monthly Download of TrigNet Data
2000250030003500400045005000
0500
100015002000
07-J
ul
07-A
ug
07-S
ep
07-O
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07-N
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07-D
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08-J
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08-M
rch
08-A
prl
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ay
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08-S
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PP Files PP Volume RT Hours RT Volume
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Plate Tectonics 1
• It has been known for many years that the earth’s crust is made up of many plates floating on the mantle. This knowledge gained through geological records. For example Mid Atlantic Ridge.
• By and large, the continents are located on these plates.Some continents are located on two or more plates
• Motion of the continents on these plates has given rise to the term “Continental Drift” “Continental Drift”
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Plate Tectonics 2
Recent Earthquakes and VolcanoesYellow = earthquakesRed = volcanoes