Presented by:Presented by:

Technical contributions from:Technical contributions from:

THE INTERNATIONAL ASSOCIATION OF THE INTERNATIONAL ASSOCIATION OF GEODESY AND PRECISE POINT GEODESY AND PRECISE POINT

POSITIONINGPOSITIONING

Sunil BisnathSunil Bisnath

(Chair IAG WG4.5.2)(Chair IAG WG4.5.2)

Hydrographic Science Research Center, Hydrographic Science Research Center, Department of Marine Science, Department of Marine Science,

The University of Southern MississippiThe University of Southern Mississippi

USM GPS Workshop 2004USM GPS Workshop 2004

16-18 March, Long Beach, Mississippi16-18 March, Long Beach, Mississippi

THE INTERNATIONAL ASSOCIATION OF THE INTERNATIONAL ASSOCIATION OF GEODESY AND PRECISE POINT GEODESY AND PRECISE POINT

POSITIONINGPOSITIONING

PURPOSE OF PRESENTATIONPURPOSE OF PRESENTATION

• To describe new International Association of To describe new International Association of Geodesy (IAG)Geodesy (IAG)

• To describe IAG precise point positioning (PPP) To describe IAG precise point positioning (PPP) activitiesactivities

• To comment on future of PPP and convergence of To comment on future of PPP and convergence of GPS processing techniquesGPS processing techniques

OVERVIEWOVERVIEW

• Description of IAGDescription of IAG

• Description of PPP Working GroupDescription of PPP Working Group

• Some recent PPP resultsSome recent PPP results

• PPP questions to considerPPP questions to consider

• Convergence of GPS processing techniquesConvergence of GPS processing techniques

DESCRIPTION OFDESCRIPTION OFINTERNATIONAL ASSOCIATION OF GEODESYINTERNATIONAL ASSOCIATION OF GEODESY

RESEARCH OBJECTIVESRESEARCH OBJECTIVES

• Promote Promote study of all scientific problems of study of all scientific problems of geodesygeodesy and encourage geodetic research and encourage geodetic research

• Promote and coordinate Promote and coordinate international cooperationinternational cooperation in this field, and promote geodetic activities in in this field, and promote geodetic activities in developing countriesdeveloping countries

• Provide, on an international basis, for Provide, on an international basis, for discussion discussion and publication of results of studiesand publication of results of studies, this research , this research and workand work

• www.iag-aig.orgwww.iag-aig.org

IAG COMMISSIONSIAG COMMISSIONS

• Commission 1. Reference framesCommission 1. Reference frames

• Commission 2. Gravity fieldCommission 2. Gravity field

• Commission 3. Earth rotation and geodynamicsCommission 3. Earth rotation and geodynamics

• Commission 4. Positioning and applicationsCommission 4. Positioning and applications

COMMISSION 4COMMISSION 4SUB-COMMISSIONSSUB-COMMISSIONS

• Sub-Commission 4.1. Multi-sensor systemsSub-Commission 4.1. Multi-sensor systems

• Sub-Commission 4.2. Applications of geodesy in Sub-Commission 4.2. Applications of geodesy in engineeringengineering

• Sub-Commission 4.3. GNSS measurement of the Sub-Commission 4.3. GNSS measurement of the atmosphereatmosphere

• Sub-Commission 4.4. Applications of satellite and Sub-Commission 4.4. Applications of satellite and airborne imaging systemsairborne imaging systems

• Sub-Commission 4.5.Sub-Commission 4.5. Next generation RTKNext generation RTK

COMMISSION 4COMMISSION 4STUDY GROUPSSTUDY GROUPS

• Study Group 4.1. Pseudolite applications in Study Group 4.1. Pseudolite applications in positioning and navigationpositioning and navigation

• Study Group 4.2. Statistics and geometry in mixed Study Group 4.2. Statistics and geometry in mixed integer linear models, with applications to GPS and integer linear models, with applications to GPS and InSARInSAR

• Study Group 1.1. Ionospheric modelling and analysis Study Group 1.1. Ionospheric modelling and analysis (joint with Commission 1) (joint with Commission 1)

• Study Group 1.2. Use of GNSS for reference frames Study Group 1.2. Use of GNSS for reference frames (joint with Commission 1)(joint with Commission 1)

SUB-COMMISSION 4.5SUB-COMMISSION 4.5WORKING GROUPSWORKING GROUPS

• Working Group 4.5.1. Network RTKWorking Group 4.5.1. Network RTK

• Working Group 4.5.2. Carrier phase-based Working Group 4.5.2. Carrier phase-based precise point positioningprecise point positioning

• Working Group 4.5.3. High precision positioning on Working Group 4.5.3. High precision positioning on buoys and moving platformsbuoys and moving platforms

DESCRIPTION OF PRECISE POINT POSITIONING DESCRIPTION OF PRECISE POINT POSITIONING WORKING GROUPWORKING GROUP

IAG WG4.5.2. CARRIER PHASE-BASEDIAG WG4.5.2. CARRIER PHASE-BASEDPRECISE POINT POSITIONINGPRECISE POINT POSITIONING

• Terms of reference:Terms of reference: To investigate issues related to To investigate issues related to development of new technology based on development of new technology based on processing of un-differenced carrier phase processing of un-differenced carrier phase observationsobservations without reference stations without reference stations

• Objectives:Objectives: To To investigate problems related to investigate problems related to development of point positioning technologydevelopment of point positioning technology, and , and to promote international research collaborationsto promote international research collaborations

• Membership:Membership: ~ ~two dozen researchers and userstwo dozen researchers and users from government, industry, and academia located from government, industry, and academia located around the globearound the globe

MAIN ACTIVITIESMAIN ACTIVITIES

• Identify technical issues and problemsIdentify technical issues and problems unique to unique to precise point positioning system developmentprecise point positioning system development

• Investigate error sourcesInvestigate error sources and handling of un-differenced and handling of un-differenced GPS observationsGPS observations

• Investigate and develop models and algorithmsInvestigate and develop models and algorithms for for processing of un-differenced GPS observationsprocessing of un-differenced GPS observations

• Investigate effects of GPS Modernization and GalileoInvestigate effects of GPS Modernization and Galileo on precise point positioningon precise point positioning

• Promote Promote collaborations collaborations and and standards developmentstandards development

• Participate in organization of international Participate in organization of international conferences conferences and workshopsand workshops

SOME RECENT PPP RESULTSSOME RECENT PPP RESULTS

Global Products for GPS Point PositioningApproaching Real-Time

Y. Gao1 and P. Heroux2

1Department of Geomatics Engineering, University of Calgary2Geodetic Survey Division, Natural Resources Canada

IGS Workshop & SymposiumBerne, Switzerland

March 1-5, 2004

GPS Products Enabling PPP

Source Accuracy Latency Update Interval Format Access

Orbit Clock

(cm) (ns)

Orbit clock Orbit clock

IGDG

(Global)

10 0.2 ? 1 sec 29 sec 1 sec Proprietary UDP

GPSC

(Regional)

10 0.5 3-5 sec 2 sec 20 sec 2 sec MRTCA Radio

UDP

Final 2 0.05 13 days Weekly 15 min 5 min SP3 RNX FTP

Rapid 3 0.1 17 hours Daily 15 min 5 min SP3 RNX FTP

UltraEST 5 0.2 3 hours 12 hr 15 min 15 min SP3 SP3 FTP

UltraPRD 10 5 None 12 hr 15 min 15 min SP3 SP3 FTP

PO

ST

-MIS

SIO

NR

EA

L-T

IME

Point Positioning Possibilities

Service Model User Data Correction

Products

User

Dynamics

Processed

Frequency

Access

SCOUT DD RNX Orbit/Network Static Dual Internet

OPUS DD RNX Orbit/Network Static Dual Internet

AUSPOS DD RNX Orbit/Network Static Dual Internet

Auto-Gipsy

PPP RNX Orbit/Clock Static Dual E-mail

CSRS-PPP

PPP RNX Orbit/Clock/GIM Static/

Kinematic

Dual/

Single

Internet

SkyFix PPP Proprietary Proprietary Static/

Kinematic

Dual SatCom

StarFire PPP Proprietary Proprietary Static/

Kinematic

Dual SatCom

PO

ST

-MIS

SIO

N/

PU

BL

ICR

EA

L-T

IME

/C

OM

ME

RC

IAL

Correction Precision: The Network Difference

GPS*C Application Input User PPP RMS

(February 1-7, 2004)

Network Data

Availability

Data

Source Orbit

Satellite Clock

Estimates

LAT

(cm)

LON

(cm)

HGT

(cm)

Regional (code)

Real-Time RT-CACS Ultra Code (Carrier filtered) 29 26 38

Regional (carrier)

Real-Time RT-CACS Ultra Code & Carrier 11 12 22

Global (carrier)

15 minutes IGS-LEO RT-IGS

Ultra Code & Carrier 5 6 10

Global

(combined)

Daily IGS IGR Code & Carrier 3 4 9

P3 – A Software Package for PPP Users

Features

• Undifferenced code/carrier processing

• Different observation model implementations

• Precise tropospheric delay and receiver clock estimation

• Static and kinematic positioning

• Forward and backward data processing

• Post-mission PPP using IGS Precise ephemeris and clock products

• Real-time PPP using JPL and NRCan real-time precise orbit/clock products

• Easy-to-use interface

• On-line view of processing results

• Various utilities

Table 3: P3TM Backward Pass Position Error Statistics Using JPL Real-Time Corrections

Position Errors Latitude (cm) Longitude (cm) Height (cm)

Mean 2.6 -0.8 -3.9 Std. Dev. 2.5 2.1 6.9 RMSE 3.6 2.3 7.9

Real-Time User Application Testing

Aircraft Trajectory

RECOMMENDATIONS

Global GPS Network

Real-Time access to tracking station data

Global GPS Products

Ultra clocks at 5-minute interval to allow more timely post-mission PPP using high-rate GPS data.

Standard correction format for real-time orbit/clock corrections

Standard protocol for Internet distribution

PPP Users

Fast ambiguity convergence algorithms for undifferenced processing (IAG SC4.5 "Next Generation RTK“)

Receiver independent real-time PPP applications

Standard serial format for orbit/clock correction input to GPS receiver.

PPP QUESTIONS TO CONSIDERPPP QUESTIONS TO CONSIDER

PPP QUESTIONS TO CONSIDER (1)PPP QUESTIONS TO CONSIDER (1)

• Filter convergence:Filter convergence:– Resolve ambiguities?Resolve ambiguities?– Different linear combinations?Different linear combinations?– Improved pseudorange handling?Improved pseudorange handling?

• Data access:Data access:– Real-time access to global tracking station data? Real-time access to global tracking station data?

e.g., free real-time IGS?e.g., free real-time IGS?– Standard protocols for access?Standard protocols for access?– Standard formats for data?Standard formats for data?

PPP QUESTIONS TO CONSIDER (2)PPP QUESTIONS TO CONSIDER (2)

• Error handling:Error handling:– Improved ionospheric modeling?Improved ionospheric modeling?– Improved tropospheric modeling?Improved tropospheric modeling?– Improved multipath mitigation?Improved multipath mitigation?

• GPS Modernization and Galileo:GPS Modernization and Galileo:– Effect of C/A on GPS L2?Effect of C/A on GPS L2?– Effect of Galileo addition?Effect of Galileo addition?

• PPP / sensor integration:PPP / sensor integration:– Effect of inertial data?Effect of inertial data?– Effect of atomic clock data?Effect of atomic clock data?

CONVERGENCE OFCONVERGENCE OFGPS PROCESSING TECHNIQUESGPS PROCESSING TECHNIQUES

PROCESSINGPROCESSINGPROGRESSION AND CONVERGENCEPROGRESSION AND CONVERGENCE

GPS code (stand-alone)

DGPS code

relative carrier (static)

DGPS code - beacon

RTK (local, baseline)

Network RTK (regional, network)

PPP (regional/global, stand-alone)

DGPS carrier- beacon??

CONVERGENCE OPTIONSCONVERGENCE OPTIONS

• No convergence:No convergence:– Nothing happensNothing happens– One “wins”One “wins”– Each “corners” a marketEach “corners” a market

• Convergence – sort of:Convergence – sort of:– Cross-checkingCross-checking– SwitchingSwitching

• Convergence:Convergence:– Initialization aidingInitialization aiding– Optimal weighting combinationOptimal weighting combination– Hybrid Hybrid true convergencetrue convergence