USM GPS RESEARCH ACTIVITIESUSM GPS RESEARCH ACTIVITIES

Presented by:Presented by:

Technical support from:Technical support from: Funding provided by:Funding provided by:

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Sunil Bisnath, David Wells, Stephan Howden, and David DoddSunil Bisnath, David Wells, Stephan Howden, and David Dodd

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

USM GPS RESEARCH ACTIVITIESUSM GPS RESEARCH ACTIVITIES

OVERVIEW OF GPS RESEARCH PROJECTSOVERVIEW OF GPS RESEARCH PROJECTS

• Design requirements for hydrographic GPS buoyDesign requirements for hydrographic GPS buoy

• Evaluation of commercial Wide Area DGPS servicesEvaluation of commercial Wide Area DGPS services

• Creation of long baseline, carrier phase GPS Creation of long baseline, carrier phase GPS databasedatabase

• Improve GPS tropospheric modelingImprove GPS tropospheric modeling

• Common themes of researchCommon themes of research

DESIGN REQUIREMENTS FORDESIGN REQUIREMENTS FORHYDROGRAPHIC GPS BUOYHYDROGRAPHIC GPS BUOY

NAVOCEANO BUOY EXPERIMENTS:NAVOCEANO BUOY EXPERIMENTS:PURPOSEPURPOSE

• To observe To observe effectiveness of effectiveness of determining water level determining water level from GPS for tidal from GPS for tidal datum determinationdatum determination

• U.S. National Ocean U.S. National Ocean Service requires water Service requires water level gauges to level gauges to measure to precision measure to precision of 10 cm (95%)of 10 cm (95%)

2001 buoydeployment

ref. stn. and2002 buoydeployment

2002/2003 buoydeployment

NAVOCEANO BUOY EXPERIMENTS:NAVOCEANO BUOY EXPERIMENTS:DEPLOYMENTSDEPLOYMENTS

5 km

UNFILTERED BUOY RTK GPS VERSUSUNFILTERED BUOY RTK GPS VERSUSTIDE GAUGE HEIGHT: APRIL 2003TIDE GAUGE HEIGHT: APRIL 2003

•~15 km baseline•WL float sol’n.

38.8 cm25.0 cm

FILTERED BUOY RTK GPS VERSUSFILTERED BUOY RTK GPS VERSUSTIDE GAUGE HEIGHT: APRIL 2003TIDE GAUGE HEIGHT: APRIL 2003

•~15 km baseline•30 min. MA filter

9.5 cm 6.3 cm

BASELINE PROCESSING CONCLUSIONS TO-DATEBASELINE PROCESSING CONCLUSIONS TO-DATE

• Simple filtering greatly improves solutionsSimple filtering greatly improves solutions

• PPK far superior than RTK for unfiltered data, but PPK far superior than RTK for unfiltered data, but marginally better than RTK for filtered datamarginally better than RTK for filtered data

• Under certain conditions, commercial RTK GPS can Under certain conditions, commercial RTK GPS can on its on its ownown estimate water level at desired accuracy estimate water level at desired accuracy

DatasetDataset BaselineBaseline 11 (cm) (cm) 95% (cm)95% (cm)

20022002 ~ 50 m~ 50 m 22 33

20012001 ~10 km~10 km 44 66

20032003 ~15 km~15 km 66 1010

Filtered, RTK solutions:Filtered, RTK solutions:

TRANSITION FROMTRANSITION FROMEXPERIMENTAL TO OPERATIONAL BUOYEXPERIMENTAL TO OPERATIONAL BUOY

• Determine tidal datum:Determine tidal datum: Capability shown by Capability shown by experiments.experiments.

• Minimum sensor suite:Minimum sensor suite: Heave and tilt sensors Heave and tilt sensors recommended.recommended.

• Buoy types:Buoy types: Deployable from survey Deployable from survey launch.launch.

• Power management:Power management: Batteries rather than solar Batteries rather than solar power.power.

• Communication links:Communication links: PPK or WADGPS rather PPK or WADGPS rather than RTK.than RTK.

EVALUATION OF COMMERCIALEVALUATION OF COMMERCIALWIDE AREA DGPS SERVICESWIDE AREA DGPS SERVICES

WHY EVALUATE THESE SERVICES?WHY EVALUATE THESE SERVICES?

• High-precision, commercial, carrier phase-based High-precision, commercial, carrier phase-based Wide Area Differential GPS (WADGPS) Wide Area Differential GPS (WADGPS) services services introducedintroduced

• Marine charting and navigation spatial resolution Marine charting and navigation spatial resolution requirements becoming more stringentrequirements becoming more stringent, , particularly in shallow waterparticularly in shallow water

• Both manufacturers and users interested in Both manufacturers and users interested in independent, comprehensive evaluationsindependent, comprehensive evaluations

SERVICES EVALUATEDSERVICES EVALUATED

• C-NavC-Nav..– Developed by C&C Technologies, Inc.Developed by C&C Technologies, Inc.– State space approachState space approach

• Starfix-HPStarfix-HP..– Developed by Fugro Chance Inc.Developed by Fugro Chance Inc.– Multi-baseline approachMulti-baseline approach

• SkyFix XPSkyFix XP..– Developed by Thales GeoSolutions Group Ltd.Developed by Thales GeoSolutions Group Ltd.– GeoSolutions since sold to FugroGeoSolutions since sold to Fugro– State space approachState space approach

STARFIX-HP STATIC TESTS:STARFIX-HP STATIC TESTS:POSITION SOLUTION 25 JULY – 7 AUG. 2003POSITION SOLUTION 25 JULY – 7 AUG. 2003

Max. = 341.2 Bias = 0.6 1 = 4.6 r.m.s. = 4.7 95% = 8.8

Max. = 81.5 Bias = 0.6 1 = 6.2 r.m.s. = 6.2 95% = 12.9

Max. = 334.4 Bias = 1.3 1 = 13.2 r.m.s. = 13.2 95% = 26.1

(All values in centimeters)(All values in centimeters)

C-NAV STATIC INITIALIZATION TESTS:C-NAV STATIC INITIALIZATION TESTS:POSITION SOLUTION 19-21 AUG. 2003POSITION SOLUTION 19-21 AUG. 2003

convergence

SUMMARY OF RESULTS FOR ALL SERVICESSUMMARY OF RESULTS FOR ALL SERVICES

Correction coverage Correction coverage areaarea

Global, less poles, orGlobal, less poles, or

~750 km from most major coasts~750 km from most major coasts

Long-term static Long-term static positioning precision positioning precision and accuracyand accuracy

5-10 cm hor. and 15-30 cm vert. (15-10 cm hor. and 15-30 cm vert. (1))

15-20 cm hor. and 25-45 cm vert. (95%)15-20 cm hor. and 25-45 cm vert. (95%)

Convergence periodConvergence period ~30 minutes~30 minutes

Kinematic Kinematic positioning precision positioning precision and accuracyand accuracy

5-10 cm hor. and 5-15 cm vert. (15-10 cm hor. and 5-15 cm vert. (1))

5-25 cm hor. and 15-35 cm vert. (95%)5-25 cm hor. and 15-35 cm vert. (95%)

POTENTIAL USAGE FOR SERVICESPOTENTIAL USAGE FOR SERVICES

• Great potential:Great potential:– Greatly reduced baseline restrictions.Greatly reduced baseline restrictions.– No base station infrastructure requirements.No base station infrastructure requirements.– Hydrographic surveys up to 1Hydrographic surveys up to 1stst order, but not order, but not

special order.special order.

• Desirable improvements:Desirable improvements:– Shortened solution convergence period.Shortened solution convergence period.– Precision.Precision.– Accuracy.Accuracy.– Quantified system integrity.Quantified system integrity.

CREATION OF LONG BASELINE,CREATION OF LONG BASELINE,CARRIER PHASE GPS DATABASECARRIER PHASE GPS DATABASE

COASTAL GPS DATABASECOASTAL GPS DATABASE

• Why:Why: Comprehensive database of diverse, high-quality Comprehensive database of diverse, high-quality coastal PPK data not availablecoastal PPK data not available

• Ideal:Ideal: Multiple baselines up to 200 km. GPS and Multiple baselines up to 200 km. GPS and weather data collected in: all weather conditions; weather data collected in: all weather conditions; various climates; all seasonsvarious climates; all seasons

• Use:Use: Validate new tropospheric modeling approaches; Validate new tropospheric modeling approaches; aid in driving evolution of long baseline, marine aid in driving evolution of long baseline, marine differential modelsdifferential models

• Access:Access: Once assembled, available to GPS Once assembled, available to GPS researchersresearchers

• Size:Size: Expected to eventually contain ~0.5 Tb of data Expected to eventually contain ~0.5 Tb of data

FERRY DATA COLLECTIONFERRY DATA COLLECTION

The Princess of Acadia

HLFX

FRED

• Bay of FundyBay of Fundy

• Long / short Long / short baseline pairsbaseline pairs

• Spatial and Spatial and temporal diversitytemporal diversity

• TemperateTemperate

• Collocation of Collocation of GPS / met. GPS / met. sensors / NWPsensors / NWP

• 1.5 – 200 km 1.5 – 200 km baselinesbaselines

• 12 month data 12 month data collectioncollection

BUOY DATA COLLECTIONBUOY DATA COLLECTION

• Northern Gulf of Northern Gulf of MexicoMexico

• Long / short Long / short baseline pairsbaseline pairs

• Single set of GPS Single set of GPS geometriesgeometries

• Sub-tropicalSub-tropical

• Collocation of Collocation of GPS / met. GPS / met. sensors / NWPsensors / NWP

• 10 – 100 km 10 – 100 km baselinesbaselines

• 12 month data 12 month data collection +collection +BUOY

BASE

IMPROVE GPS TROPOSPHERIC MODELINGIMPROVE GPS TROPOSPHERIC MODELING

WHY CONCENTRATE ON THE TROPOSPHERE?WHY CONCENTRATE ON THE TROPOSPHERE?

• Mis-modeling of differential troposphere seen as Mis-modeling of differential troposphere seen as largest limiting error source in coastal PPK GPSlargest limiting error source in coastal PPK GPS

• Large spatial and temporal variability in differential Large spatial and temporal variability in differential delay, especially significant for difficult to model “wet” delay, especially significant for difficult to model “wet” componentcomponent

Improved means of modeling requiredImproved means of modeling required

Methods for applying modeling improvements in Methods for applying modeling improvements in processing requiredprocessing required

STRATEGY FORSTRATEGY FORIMPROVED TROPOSPHERIC MODELINGIMPROVED TROPOSPHERIC MODELING

1.1. Review performance of Review performance of existing GPS tropospheric existing GPS tropospheric delay modelsdelay models

2.2. Determine feasibility and potential of Determine feasibility and potential of estimating estimating residual tropospheric delayresidual tropospheric delay

3.3. Evaluate application of Evaluate application of in situ meteorological in situ meteorological sensor measurementssensor measurements

4.4. Analyze level of benefit of employing Analyze level of benefit of employing regional regional weather dataweather data

5.5. Customize Customize subset of these strategiessubset of these strategies

IMPROVED PPK GPS ALGORITHMSIMPROVED PPK GPS ALGORITHMS

• To validate modeling improvements and to make To validate modeling improvements and to make them usefulthem useful

• Using Using commercial software:commercial software:– ““DynaPos” from The XYZ’s of GPS, Inc.DynaPos” from The XYZ’s of GPS, Inc.– ““GrafNav” from Waypoint Consulting Inc.GrafNav” from Waypoint Consulting Inc.

• Enhancement of Enhancement of academic software:academic software:– ““UNBRTK” from University of New Brunswick.UNBRTK” from University of New Brunswick.– ““USMOTF” under development at University of USMOTF” under development at University of

Southern MississippiSouthern Mississippi

EXAMPLE OF IMPROVEMENT:EXAMPLE OF IMPROVEMENT:NOAA EXPERIMENTAL TROPOSPHERIC PRODUCTNOAA EXPERIMENTAL TROPOSPHERIC PRODUCT

• NOAA developing nationwide troposphere and NOAA developing nationwide troposphere and ionosphere delay productsionosphere delay products

• Tropospheric product based on available weather Tropospheric product based on available weather information and estimated tropospheric delay from information and estimated tropospheric delay from GPS networkGPS network

• Input: user location and timeInput: user location and time

• Output: wet and hydrostatic tropospheric delayOutput: wet and hydrostatic tropospheric delay

• Southern Miss beginning an assessment of quality Southern Miss beginning an assessment of quality and utility of productand utility of product

• NOAA zenith NOAA zenith wet delaywet delay

• 22 July 200322 July 2003

• U.S. NortheastU.S. Northeast

• Zenith delay Zenith delay range: range: 10 to 30 cm10 to 30 cm

Slant delay Slant delay range: range: 10 to ~300 cm10 to ~300 cm

COMMON THEMES OF RESEARCHCOMMON THEMES OF RESEARCH

THEMESTHEMES

• Require higher accuracy and integrity for GPS-based Require higher accuracy and integrity for GPS-based positioning in coastal areas – for individual projects positioning in coastal areas – for individual projects and for integration of projectsand for integration of projects

• Tropospheric mis-modeling needs to be reduced to Tropospheric mis-modeling needs to be reduced to extend GPS baselinesextend GPS baselines

• Need to define current capabilitiesNeed to define current capabilities

• Need to improve performanceNeed to improve performance

DEFINITIONDEFINITION OF COASTAL GPS ACCURACY OF COASTAL GPS ACCURACY

Increasing baseline length

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IMPROVEMENTIMPROVEMENT OF COASTAL GPS ACCURACY OF COASTAL GPS ACCURACY

Increasing baseline length

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