1. gnss precise point positioning challenges and prospects

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

RMIT University©2012 Survey Expo and the ISV Annual General Meeting 2

Overview

1. Introduction to Precise Point Positioning

2. Benefits and limitations

3. Use and applications

4. Multi-GNSS and future prospects



International GNSS Service

RMIT University©2012 5

GNSS Positioning Techniques

Absolute PointPositioning

Relative Positioning

Precise PointPositioning (PPP)

Introduction – GNSS Positioning Techniques

Survey Expo and the ISV Annual General Meeting


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


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)


(1) (Pr)

)(Pr

rel

tropionorb

d

ddddTdtcsr

p

Precise Point Positioning (PPP)

(2) )(

)(

pwrel

tropionorb

ddN

ddddTdtcsr

p

LL

L

(3) (Pr).Pr ZPDMdcdtsr

p ion

(4) )(. LLL NZPDMdcdtsr

p ion

ZPDM .

ZPDM .

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


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


Australia National Positioning Infrastructure (NPI)


Limitations and Benefits of PPP (vs Relative Positioning)


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


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


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…..


Market Share in 2012 and 2015 (Prediction)


Network RTK Standard PPPNetwork RTK

Augmented PPPPPP/RTK


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


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

Survey Expo and the ISV Annual General Meeting

Post-processed Static PPP Test in Australia and Antarctica

RMIT University©2012 17

• 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)


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


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)


QZSS GALILEOGLONASS

COMPASS

GLONASS

New GNSS signals: how to deal with the plethora of observables?


• 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


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


“ 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…..


• ISV has 370 fee paying members, of which 15 (4%) are female.

Source: Robyn McCutcheon (2012), FIG Working Week

More Statistics.....


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


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


Inspire, Engage, Encourage and Empower

– role models and mentors– remove stereotypes– inclusive culture– scholarships and awards– ‘branding’


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]


Thank you for your attention!

1. gnss precise point positioning challenges and prospects

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