P. Alves and G. Lachapelle University of Calgary USM GPS Workshop Carrier Phase GPS Navigation for...

P. Alves and G. LachapelleUniversity of Calgary

USM GPS Workshop

Carrier Phase GPS Navigation for Hydrographic Surveys, and Seamless Vertical Datums

March 16 – 18, 2004

P. Alves and G. LachapelleUniversity of Calgary

USM GPS Workshop

Carrier Phase GPS Navigation for Hydrographic Surveys, and Seamless Vertical Datums

March 16 – 18, 2004

Multiple Reference Station DGPS RTK For Sub-decimeter

Level 3D Positioning

Multiple Reference Station DGPS RTK For Sub-decimeter

Level 3D Positioning

USM GPS Workshop 2004 USM GPS Workshop 2004 22

OverviewOverview• Network RTK

• MultiRef™ approach• Large-scale network (USCG NDGPS) initial results • Medium-scale test network on-going evaluation

program

• In-receiver approach to Network RTK• Concept• Results (Campania Network)

• The Future of Network RTK• Modernized GPS and GALILEO

• Network RTK• MultiRef™ approach• Large-scale network (USCG NDGPS) initial results • Medium-scale test network on-going evaluation

program

• In-receiver approach to Network RTK• Concept• Results (Campania Network)

• The Future of Network RTK• Modernized GPS and GALILEO


Why Use Network RTK?Why Use Network RTK?

Fixed ambiguities are required for centimeter level 3D positioning. The type of ambiguity is important.

Fixed ambiguities do not guarantee cm-level accuracy, especially in height.

Fixed ambiguities are required for centimeter level 3D positioning. The type of ambiguity is important.

Fixed ambiguities do not guarantee cm-level accuracy, especially in height.

Position accuracy with WL ambiguities


Reduction of Measurement Errors

Reduction of Measurement Errors

• To achieve cm-level positioning both L1 and WL ambiguities (for ionosphere-free fixed ambiguities) are required.

• L1 and WL ambiguity resolution is only reliable with 5 -10 km of the nearest reference station in single reference station mode.

• Network RTK models the errors that limit the range of ambiguity resolution.

• To achieve cm-level positioning both L1 and WL ambiguities (for ionosphere-free fixed ambiguities) are required.

• L1 and WL ambiguity resolution is only reliable with 5 -10 km of the nearest reference station in single reference station mode.

• Network RTK models the errors that limit the range of ambiguity resolution.


Multiple Reference Station RTKMultiple Reference Station RTK

-100 -80 -60 -40 -20 0 20 40 60 80 100-100

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Easting (km)

Nor

thin

g (k

m)

Desired Coverage Area

Independent ref. receiversNot Efficient - too many rx

-100 -80 -60 -40 -20 0 20 40 60 80 100-100

-80

-60

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Easting (km)

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rth

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Desired Coverage Area

Network of reference receivers


How It’s DoneHow It’s Done

Land-line/Wireless

Reference Station NetworkControl Center

Output CorrectionsInput Observations

GPS Receiver

User

RTCM

Data from the reference station network is sent to the control center

Control center calculates network corrections and applies them to the RS data

User processes single RS (corrected)


U of C MultiRef™ MethodU of C MultiRef™ Method

Modeling of regional errors using reference stations interactively

Three stage process:1. Resolution of network ambiguities (Fixed or

float). Used to measure error levels at the reference station locations

2. Interpolation of the errors to the location of the rover using least squares prediction

3. Application of the corrections to the rover and processing of rover data in real-time

Modeling of regional errors using reference stations interactively

Three stage process:1. Resolution of network ambiguities (Fixed or

float). Used to measure error levels at the reference station locations

2. Interpolation of the errors to the location of the rover using least squares prediction

3. Application of the corrections to the rover and processing of rover data in real-time


MultiRef™ USCG NDGPS TestingMultiRef™ USCG NDGPS Testing

• Two sub-networks selected

• Two scenarios selected for each sub-network

• East coast sub-network within the NOAA GPS-Met test network


North West NetworkNorth West Network

140

100150

540 km

100 km150

140

150

140

540 km

Reference station

Rover station

Scenario NW1

Scenario NW2


Observation Domain NW Network

Observation Domain NW Network

RMS (cm)

Single baseline

NW1 NW2

L1 13.4 12.0 12.4

L2 21.9 19.7 20.3

WL 16.9 15.2 15.7

IF 0.7 0.5 0.5

GF 8.5 7.7 7.9

Improvement (%)

NW1 NW2

L1 10.2 7.4

L2 10.1 7.2

WL 10.2 7.4

IF 19.7 21.2

GF 10.1 7.3

100 km150

140

150

140

540 km

Reference station

Rover station

Scenario NW1 Scenario NW2


Position Domain NW Network

Position Domain NW Network

North East Up 3D

Single baseline (cm) 5.5 5.3 14.8 16.7

NW1 Network (cm) 4.2 4.9 10.6 12.4

Improvement (%) 23.7 7.0 28.3 25.4

NW2 Network (cm) 3.9 5.1 9.4 11.4

Improvement (%) 28.4 3.8 36.3 31.5

100 km150

140

150

140

540 km

Reference station

Rover station

Scenario NW1 Scenario NW2


North East NetworkNorth East Network

470448 km227

167

Scenario NE2

470

448 km

167

Scenario NE1

470

448 km227

Reference station

Rover station


Observation Domain NE Network

Observation Domain NE Network

Scenario NE1

470

448 km227

RMS (cm)

NE1 NE2

Single baseline

Net-work

Single baseline

Net-work

L1 16.4 12.9 15.6 13.0

L2 26.9 21.1 25.6 21.4

WL 21.2 16.5 20.7 17.4

IF 0.7 0.6 1.0 1.0

GF 10.6 8.3 10.2 8.5

Improvement (%)

NE1 NE2

L1 21.3 16.2

L2 21.6 16.4

WL 22.1 16.3

IF 8.7 6.7

GF 21.9 16.5

Scenario NE2

470

448 km

167


Position Domain NE Network

Position Domain NE Network

North East Up 3D

NE1 Single baseline (cm) 4.5 5.5 10.9 13.0

Network (cm) 3.9 5.0 9.9 11.7

Improvement (%) 12.9 8.7 10.0 10.0

NE2 Single baseline (cm) 5.7 5.1 14.0 15.9

Network (cm) 5.3 5.3 11.9 14.1

Improvement (%) 6.2 -3.1 15.1 11.9

Scenario NE1

470

448 km227

Scenario NE2

470

448 km

167


NOAA GPS-Met NetworkNOAA GPS-Met Network

• Troposphere grid model based on over 300 GPS stations

• Test bed is located in North East USA

• By 2010, GPS-Met atmospheric delay corrections will cover CONUS

• Troposphere grid model based on over 300 GPS stations

• Test bed is located in North East USA

• By 2010, GPS-Met atmospheric delay corrections will cover CONUS


#4: NE Network + NOAA Troposphere Model

#4: NE Network + NOAA Troposphere Model

470448 km227

167

Scenario NE2

470

448 km

167

Scenario NE1

470

448 km227

Reference station

Rover station


Observation Domain (NE1 + Troposphere Model)

Observation Domain (NE1 + Troposphere Model)

NE 1

RMS (cm)

Single baseline Network

Modified Hopfield

NOAA Modified Hopfield

NOAA

L1 16.6 16.8 11.7 12.8

L2 27.3 27.7 19.3 21.0

WL 21.3 21.7 15.5 16.7

IF 0.9 0.7 0.7 0.6

GF 10.7 10.9 7.6 8.3

Improvement (%) L1 L2 WL IF GF

Single baseline

NOAA -1.2 -1.6 -1.8 26.4 -2.1

Network Modified Hopfield

29.8 29.4 27.5 23.1 28.7

Tropo 23.4 22.9 21.8 36.3 22.1

Scenario NE1

470

448 km227


Position Domain (NE1 + Troposphere Model)


Scenario NE1

470

448 km227

RMS (cm) North East Up 3D

Single baseline

Modified Hopfield

5.5cm 6.5 18.9 20.8cm

NOAA 4.8 7.4 13.1 15.8


6.3 8.2 14.0 17.4

NOAA 4.5 7.0 12.6 15.1

Improvement (%) North East Up 3D

Single baseline

NOAA 12.5 13.5 30.7 23.9%


-13.8 26.0 26.2 16.3

NOAA 18.1 -6.6 33.4 27.3




Scenario NE2

470

448 km

167

RMS (cm) North East Up 3D

Single baseline

Modified Hopfield

5.4 4.9 25.4 26.4cm

NOAA 4.5 3.9 19.5 20.4


4.6 5.5 19.1 20.2

NOAA 3.8 4.4 14.5 15.6

Improvement (%) North East Up 3D

Single baseline

NOAA 16.8 19.6 23.1 22.7%


15.7 13.4 24.9 23.3

NOAA 29.4 8.5 43.0 40.8


USCG NDGPS Test SummaryUSCG NDGPS Test Summary

• Network RTK significantly improves performance in both observation and position domains.

• However, sub-decimeter level positioning is not possible on this large scale network.

• A smaller, medium scale network, is better suited to achieving centimeter level 3D positioning.

• Network RTK significantly improves performance in both observation and position domains.

• However, sub-decimeter level positioning is not possible on this large scale network.

• A smaller, medium scale network, is better suited to achieving centimeter level 3D positioning.


U of C Southern Alberta Network (SAN)

U of C Southern Alberta Network (SAN)

GPS Reference Stations

GPS Reference Stations with MET instruments

30 60 90 120km

14 NovAtel Modulated Precision Clock (MPC) Receivers.

10 Digiquartz MET3A Fan-Aspirated Meteorological Measurement Systems.


SAN Research ActivitiesSAN Research Activities• Network RTK

• Correction-based Network RTK methods• In-receiver Network RTK• Error modeling studies• Effects of network geometry and topology• Integration of Network RTK with other measurement

instruments (i.e. inertial measurement units)

• GPS Meteorology• Ground moisture correlation with GPS derived perceptible

water vapor• GPS storm signatures• GPS occultation research• Regional tropospheric water vapor modeling

• Network RTK• Correction-based Network RTK methods• In-receiver Network RTK• Error modeling studies• Effects of network geometry and topology• Integration of Network RTK with other measurement

instruments (i.e. inertial measurement units)

• GPS Meteorology• Ground moisture correlation with GPS derived perceptible

water vapor• GPS storm signatures• GPS occultation research• Regional tropospheric water vapor modeling


In-Receiver Network RTK Approach

In-Receiver Network RTK Approach

The roving receiver uses integrates the data from all available reference station to achieve network-based high accuracy 3D positions.

The roving receiver uses integrates the data from all available reference station to achieve network-based high accuracy 3D positions.

Land-line/Wireless

Reference Station Network

GPS Receiver

User


Network Processing

Rover Positioning

AdvantagesAdvantages

Correction-based Network RTKCorrection-based Network RTK

Control CenterNetwork

Processing

RS

RS

RS

Rover Positioning

One-way communication

In-Receiver Network RTKIn-Receiver Network RTK

RS

RS

RSTwo-way communication

The rover data can assist with network processing


Campania NetworkCampania Network12 Station network (50 km average inter-receiver distance)

Six scenarios tested using 24 hours of data at 1 Hz.

Rover Reference

Station

Distance

(km)

BENE AVEL 22

CASE PORT 28

AVEL ARIA 33

PADU VLUC 35

ISCH PORT 38.5

BATT AVEL 39


3D Position Accuracy3D Position Accuracy


3D Position Accuracy Summary

3D Position Accuracy Summary

Case Length

(km)

3D RMS (cm) Improvement

(%)Single RS RTK

Network RTK

AVELBENE 22 12.2 3.5 71 %

PORTCASE 28 12.7 5.8 55 %

ARIAAVEL 33 12.7 4.7 63 %

VLUCPADU

35 18.3 3.3 82 %

PORTISCH 38.5 22.5 3.4 85 %

AVELBATT 39 26.9 3.5 87 %


Future of Network RTK:Modernized GPS and GALILEO

Future of Network RTK:Modernized GPS and GALILEO

• Approximately 60 satellites.• Three frequency observations per satellite.

Past and current research projects:• Dilution of precision, availability and reliability with GPS,

GALILEO, and combined GPS and GALILEO.

• Ambiguity resolution and positioning accuracy with three frequency GPS, GALILEO and combined GPS and GALILEO.

• GPS and GALILEO advanced integration methods (GPS and GALILEO crossed).

• Triple frequency ionosphere modeling for long baseline ambiguity resolution and precise positioning.

All of these research topics are necessary for GPS and GALILEO Network RTK.

• Approximately 60 satellites.• Three frequency observations per satellite.

Past and current research projects:• Dilution of precision, availability and reliability with GPS,

GALILEO, and combined GPS and GALILEO.

• Ambiguity resolution and positioning accuracy with three frequency GPS, GALILEO and combined GPS and GALILEO.

• GPS and GALILEO advanced integration methods (GPS and GALILEO crossed).

• Triple frequency ionosphere modeling for long baseline ambiguity resolution and precise positioning.

All of these research topics are necessary for GPS and GALILEO Network RTK.


Effects of Modernized GPS and GALILEO on Single RS RTK

Effects of Modernized GPS and GALILEO on Single RS RTK

Simulated triple frequency data with 3 ppm differential errors

Percentage of correctly resolved ambiguity sets

Time to fix ambiguities correctly

Plotted as a function of distance between the rover and reference station.


Effects of Modernized GPS and GALILEO on Network RTK

Effects of Modernized GPS and GALILEO on Network RTK

• Faster network ambiguity resolution.

• More precise measure of the errors at the reference stations.

• Better modeling of the regional errors.

• Reduction of measurement errors at the rover.

• Faster network ambiguity resolution.

• More precise measure of the errors at the reference stations.

• Better modeling of the regional errors.

• Reduction of measurement errors at the rover.


ReferencesReferences• Fortes, L. (2002) Optimising the Use of GPS Multi-Reference Stations

for Kinematic Positioning, Ph.D. Thesis, URL: http://www.geomatics.ucalgary.ca/links/GradTheses.html

• Julien, O., M.E. Cannon, P. Alves, and G. Lachapelle (2004) Triple Frequency Ambiguity Resolution Using GPS/GALILEO, European Journal of Navigation, June

• Liu, J., M.E. Cannon, P. Alves, M.G. Petovello, G. Lachapelle, G. Macgougan, and L. deGrout (2003) Performance Comparison of Single and Dual Frequency GPS Ambiguity Resolution Strategies, GPS Solutions, Vol. 7, No. 2, (July Issue), 87 – 100, Springer-Verlag

• Pugliano, G. (2002) Tecnica GPS Multi-Reference Station Prencipie Applicazione Del Sistema MULTIREF™, Ph.D. Thesis, URL: http://www.geomatics.ucalgary.ca/links/GradTheses.html

• Pugliano, G., P. Alves, M.E. Cannon, and G. Lachapelle (2003) Performance Analysis of a Post-Mission Multi-Reference RTK DGPS Positioning Approach. Proceedings of the International Association of Institutes of Navigation World Congress (October 2003, Berlin, Germany)

• Fortes, L. (2002) Optimising the Use of GPS Multi-Reference Stations for Kinematic Positioning, Ph.D. Thesis, URL: http://www.geomatics.ucalgary.ca/links/GradTheses.html

• Julien, O., M.E. Cannon, P. Alves, and G. Lachapelle (2004) Triple Frequency Ambiguity Resolution Using GPS/GALILEO, European Journal of Navigation, June

• Liu, J., M.E. Cannon, P. Alves, M.G. Petovello, G. Lachapelle, G. Macgougan, and L. deGrout (2003) Performance Comparison of Single and Dual Frequency GPS Ambiguity Resolution Strategies, GPS Solutions, Vol. 7, No. 2, (July Issue), 87 – 100, Springer-Verlag

• Pugliano, G. (2002) Tecnica GPS Multi-Reference Station Prencipie Applicazione Del Sistema MULTIREF™, Ph.D. Thesis, URL: http://www.geomatics.ucalgary.ca/links/GradTheses.html

• Pugliano, G., P. Alves, M.E. Cannon, and G. Lachapelle (2003) Performance Analysis of a Post-Mission Multi-Reference RTK DGPS Positioning Approach. Proceedings of the International Association of Institutes of Navigation World Congress (October 2003, Berlin, Germany)


Additional InformationAdditional Information

Position, Location, and Navigation Projects:

http://plan.geomatics.ucalgary.ca

Network RTK at PLAN:

http://plan.geomatics.ucalgary.ca/multiref_project.html

Geomatics Engineering graduate theses:

http://www.geomatics.ucalgary.ca/links/GradTheses.html

Position, Location, and Navigation Projects:

http://plan.geomatics.ucalgary.ca

Network RTK at PLAN:

http://plan.geomatics.ucalgary.ca/multiref_project.html

Geomatics Engineering graduate theses:

http://www.geomatics.ucalgary.ca/links/GradTheses.html

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