P. Alves and G. Lachapelle University of Calgary USM GPS Workshop Carrier Phase GPS Navigation for Hydrographic Surveys, and Seamless Vertical Datums March 16 – 18, 2004 P. Alves and G. Lachapelle University 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

USM GPS Workshop Overview 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

USM GPS Workshop 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

USM GPS Workshop 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 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 km of the nearest reference station in single reference station mode. Network RTK models the errors that limit the range of ambiguity resolution.

USM GPS Workshop Multiple Reference Station RTK Independent ref. receivers Not Efficient - too many rx Ref. Easting (km) Northing (km) Desired Coverage Area Network of reference receivers

USM GPS Workshop How It’s Done Land-line/Wireless Reference Station Network Control Center Output Corrections Input 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)

USM GPS Workshop U 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

USM GPS Workshop MultiRef™ 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 Two sub-networks selected Two scenarios selected for each sub-network East coast sub- network within the NOAA GPS-Met test network

USM GPS Workshop North West Network

USM GPS Workshop Observation Domain NW Network RMS (cm) Single baseline NW1NW2 L L WL IF GF Improvement (%) NW1NW2 L L WL IF GF

USM GPS Workshop Position Domain NW Network NorthEastUp3D Single baseline (cm) NW1Network (cm) Improvement (%) NW2Network (cm) Improvement (%)

USM GPS Workshop North East Network

USM GPS Workshop Observation Domain NE Network RMS (cm) NE1NE2 Single baseline Net- work Single baseline Net- work L L WL IF GF Improvement (%) NE1NE2 L L WL IF GF

USM GPS Workshop Position Domain NE Network NorthEastUp3D NE1Single baseline (cm) Network (cm) Improvement (%) NE2Single baseline (cm) Network (cm) Improvement (%)

USM GPS Workshop NOAA 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

USM GPS Workshop #4: NE Network + NOAA Troposphere Model

USM GPS Workshop Observation Domain (NE1 + Troposphere Model) NE 1 RMS (cm) Single baselineNetwork Modified Hopfield NOAAModified Hopfield NOAA L L WL IF GF Improvement (%)L1L2WLIFGF Single baseline NOAA NetworkModified Hopfield Tropo

USM GPS Workshop Position Domain (NE1 + Troposphere Model) RMS (cm)NorthEastUp3D Single baseline Modified Hopfield 5.5cm cm NOAA NetworkModified Hopfield NOAA Improvement (%)NorthEastUp3D Single baseline NOAA % NetworkModified Hopfield NOAA

USM GPS Workshop Position Domain (NE1 + Troposphere Model) RMS (cm)NorthEastUp3D Single baseline Modified Hopfield cm NOAA NetworkModified Hopfield NOAA Improvement (%)NorthEastUp3D Single baseline NOAA % NetworkModified Hopfield NOAA

USM GPS Workshop USCG 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.

USM GPS Workshop U of C Southern Alberta Network (SAN) GPS Reference Stations GPS Reference Stations with MET instruments km 14 NovAtel Modulated Precision Clock (MPC) Receivers. 10 Digiquartz MET3A Fan- Aspirated Meteorological Measurement Systems.

USM GPS Workshop SAN 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

USM GPS Workshop 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. Land-line/Wireless Reference Station Network GPS Receiver User

USM GPS Workshop Network Processing Rover Positioning Advantages Correction-based Network RTK Control Center Network Processing RS Rover Positioning One-way communication In-Receiver Network RTK RS Two-way communication The rover data can assist with network processing

USM GPS Workshop Campania Network 12 Station network (50 km average inter- receiver distance) Six scenarios tested using 24 hours of data at 1 Hz. RoverReference Station Distance (km) BENEAVEL22 CASEPORT28 AVELARIA33 PADUVLUC35 ISCHPORT38.5 BATTAVEL39

USM GPS Workshop D Position Accuracy

USM GPS Workshop D Position Accuracy Summary CaseLength (km) 3D RMS (cm)Improvement (%) Single RS RTK Network RTK AVEL  BENE % PORT  CASE % ARIA  AVEL % VLUC  PADU % PORT  ISCH % AVEL  BATT %

USM GPS Workshop 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.

USM GPS Workshop 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.

USM GPS Workshop 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.

USM GPS Workshop References Fortes, L. (2002) Optimising the Use of GPS Multi-Reference Stations for Kinematic Positioning, Ph.D. Thesis, URL: 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: 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: 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: 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)

USM GPS Workshop Additional Information Position, Location, and Navigation Projects: Network RTK at PLAN: Geomatics Engineering graduate theses: Position, Location, and Navigation Projects: Network RTK at PLAN: Geomatics Engineering graduate theses: