1. GNSS Precise Point Positioning Challenges and Prospects
Dr Suelynn ChoySchool of Mathematical and Geospatial SciencesRMIT University, Melbourne, [email protected]
2. Engaging Women in Surveying: A Personal Perspective
1. GNSS Precise Point Positioning Challenges and Prospects
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Overview
1. Introduction to Precise Point Positioning
2. Benefits and limitations
3. Use and applications
4. Multi-GNSS and future prospects
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International GNSS Service
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GNSS Positioning Techniques
Absolute PointPositioning
Relative Positioning
Precise PointPositioning (PPP)
Introduction – GNSS Positioning Techniques
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Absolute Point Positioning (Standard Positioning Service)
• Original design of GPS/GNSS
• Position of a point is determined using code measurement from a single GPS/GNSS receiver, along with the broadcast navigation message
• Satellite, atmospheric and receiver errors are not (marginally) corrected
• Low accuracy (metres level)
(X, Y, Z, t)
Distance = Velocity * Travel Time
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Relative/Differential Positioning
• Simultaneous observations from 2 (or more) GPS/GNSS receivers
• Satellite orbit, ionospheric and tropospheric errors cancel out
• Double differencing to remove satellite and receiver clock errors
• High accuracy (centimetre level)
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Precise Point Positioning (PPP)
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Key to PPP:• Precise satellite orbits and clock corrections• Additional errors modeling• Carrier phase measurements
SPS vs PPP• Unlike the GPS Standard Positioning Service (SPS), Precise Point
Positioning (PPP) allows a dual-frequency GPS user to determine position at the decimetre / centimetre error level in kinematic / static mode, using consistent, precise satellite orbits and clocks
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m-level real-time broadcast GPS orbit and clock
information
User GPS satellite tracking information
(code-only observations)
m-level user position estimates
+
cm-level real-time or post-processed precise GPS orbit
and clock information
Additional error modelling
Standard Positioning ServicePrecise Point Positioning
=
User GPS satellite tracking information
(code and carrier phase observations)
dm- to cm-level user position estimates
+
=
+
Victoria CORS Infrastructure – GPSnet
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Australia National Positioning Infrastructure (NPI)
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Limitations and Benefits of PPP (vs Relative Positioning)
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Limitations Benefits
Direct access to the global ITRF
reference frame
Reduce computation burden and financial
cost
Not constrained by baseline length/base
stations
Sensitive to clock errors and to
incompatibilities
Slightly lower positional accuracy
Long solution convergence times
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Network RTK Standard PPP
• Surveying• Mapping/GIS• Engineering• Construction• Machine control• Precision agriculture• Deformation monitoring• GNSS meteorology• …………
• Plate tectonics studies• Offshore positioning• Airborne mapping • Disaster monitoring• LEO orbit determination• …………
Then…..
Source: Tamas Horvath (2012), PPP-RTK Symposium
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Network RTK Augmented PPP / PPP-RTK
• Surveying• Mapping/GIS• Engineering• Construction• Machine control• Precision agriculture• Deformation monitoring• GNSS meteorology• …………
• Plate tectonics studies• Offshore positioning• Airborne mapping • Disaster monitoring• LEO orbit determination• …………
Now…..
Source: Tamas Horvath (2012), PPP-RTK Symposium
Market Share in 2012 and 2015 (Prediction)
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Network RTK Standard PPPNetwork RTK
Augmented PPPPPP/RTK
Source: Tamas Horvath (2012), PPP-RTK Symposium
Use and Applications• Commercial applications:
– Trimble CentrePoint™ RTX™– NavCom Global StarFire™ Service– Fugro’s Precise (Point) Positioning Service
– Eplus, XP, G2– Veripos Ultra (Ultra²) and APEX (APEX²) Service
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PPP is feasible for positioning and navigation in remote areas or regions of low GNSS reference stations
PPP is feasible for positioning and navigation in remote areas or regions of low GNSS reference stations
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Post-processed Static PPP Test in Australia and Antarctica
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• Date: 1 – 31 January 2012
• Observations: 30s, dual-frequency, 24 hours
• Stations: 13 Australian and Antarctica
Regional GNSS stations
• Orbits and clocks: IGS rapid products
• ‘Fixed’ coordinates: APREF solutions (relative)
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Post-processed Kinematic PPP Test
• Date: 15 November 2010
• Observations: 1s, dual-frequency, 4.5 hours
• Data: Airborne LiDAR survey, Benalla, Victoria
• Orbits and clocks: IGS final products
• ‘Fixed’ coordinates: Baseline (one station) processing (RTKLIB)
Mean (m) STD (m)BC AC BC AC
E ‐0.01 ‐0.00 0.08 0.03N 0.04 0.02 0.09 0.03H ‐0.11 ‐0.12 0.17 0.07
Note: BC – before solutions convergenceAC – after solutions convergence (>30mins)
Current Status
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Measurements Mode RMS (cm)East North Up
Dual-frequency Daily static <0.5 <0.5 <1Hourly static ~4 ~2 ~3Post-processed kinematic ~5 ~4 ~10Real-time kinematic <10 <10 <20
Single-frequency Post-processed kinematic ~25 ~25 ~50Real-time kinematic ~40 ~40 ~50
Source: Jianghui Geng (2010), PhD thesis
RMS of the differences between GPS-PPP positions and ground truths
Note: No PPP ambiguity resolution
Multi-GNSS – System Overview• Global systems
– USA Global Positioning System (GPS)– Russia Global’naya Navigatsionnaya Sputnikovaya Sistema
(GLONASS)– EU Galileo– China Compass/Beidou
• Regional and augmentation systems– Japan Quasi-Zenith Satellite System (QZSS)– India Indian Regional Navigation Satellite System (IRNSS)
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QZSS GALILEOGLONASS
COMPASS
GLONASS
New GNSS signals: how to deal with the plethora of observables?
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• Date: 31 September 2012 (24 hours)
• Location: Federation Square, Melbourne
• GNSS: GPS, GLONASS, Galileo, Compass/Beidou, QZSS
Number of SVs
Future Prospects of PPP
• Quality control for real-time PPP– consistency– integrity
• PPP-AR for rapid convergence and re-convergence – ionospheric constraints: spatial and temporal constraints– regional augmentation
• Real-time dissemination of satellite products– e.g. satellite hardware biases from CNES and others
• Multi-frequency and multi-GNSS PPP– availability of triple frequency carrier phase measurements – coexistence of several constellations
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PPP with RTK-like performance (that is RTK without reference stations) is still not possible ……
But recent research has brought the two techniques much closer.
PPP with RTK-like performance (that is RTK without reference stations) is still not possible ……
But recent research has brought the two techniques much closer.
2. Engaging Women in Surveying: A Personal Perspective
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“ In an era when women are increasingly prominent in medicine, law and business, why are there so few women scientists, engineers and surveyors? ”
Some Statistics…..
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• ISV has 370 fee paying members, of which 15 (4%) are female.
Source: Robyn McCutcheon (2012), FIG Working Week
More Statistics.....
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Source: Robyn McCutcheon (2012), FIG Working Week
Only 4% of women are in the surveying workforce
19% of women in spatial industry are from Victoria
Statistics of Male and Female Licensed Surveyors
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Jurisdiction Males (practising)
Total Males
Females (practising)
Total Females
Total Licensed Surveyors
Females Percentage of Total
VIC 421 523 12 13 536 2.4% NSW 955 955 14 14 969 1.4%ACT - 76 - 1 77 1.2%QLD 702 4 706 0.5%NT - 84 - 2 86 2.3%WA 254 634 1 4 638 0.6%SA 128 140 2 2 142 1.4%TAS - 102 - 1 103 0.9%NZ - 651 - 47 698 6.7%
Figures are as it 12 April 2012. Source: Robyn McCutcheon (2012), FIG Working Week
Why Women Don’t Go Into Surveying?
Reasons Against
Surveying
Stereotypes
Work Life Balance (career breaks/
childcare)
Lack of Role
ModelsLack of
Awareness
Poor Careers Advice
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Inspire, Engage, Encourage and Empower
– role models and mentors– remove stereotypes– inclusive culture– scholarships and awards– ‘branding’
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Why?
How?
• Equality and diversity– better services and products– robust and balanced industry
Could it be serendipity? .... NO!
Attract, Retain, Develop, Celebrate
Contact:
Dr Suelynn ChoySchool of Mathematical and Geospatial SciencesRMIT University, Melbourne, [email protected]
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Thank you for your attention!