Advances in GNSS Technology and it s Application to Tidal Derivation Tim Painter Chief Surveyor Fugro Survey Africa Pty Ltd John Vint Survey and Starfix Product Manager Fugro Survey AS, Norway
Scope of Presentation History of GNSS Positioning Latest Developments within GNSS (PPP-IAR) System Accuracies for Latest GNSS Systems Derivation of Tidal Data from GNSS Summary
Transit system first used High frequency DGPS service HP dual-frequency service 1984 1996 1974 1986 2001 Starfix positioning system Satellite based DGPS 4 www.fugro.com
XP precise point positioning (PPP) service G4 multi-constellation PPP service 2009 2015 2006 2014 G2 GPS & GLONASS PPP service G2+ ambiguity-fixed PPP service 5 www.fugro.com
Latest GNSS Developments within Fugro
Starfix.G2 Dual frequency receiver GPS +GLONASS PPP position solution Fugro network of reference stations Accuracies are typically better than 10cm (95%) in horizontal and vertical
Starfix.G2 - DataFlow
Starfix.G4 Newest addition to Fugro positioning systems Precise point positioning (PPP) solution Orbit and clock corrections for GPS, GLONASS, Beidou and Galileo Galileo corrections available when Initial Operational Capability (IOC) announced by the European Union Improved availability and reliability
Starfix.G2+ Starfix.G2+ is a new service which improves the accuracy of the existing Starfix.G2 service. The Starfix.G2+ service uses a global network of reference stations to calculate an additional set of corrections that are sent to the user, which allows ambiguities to be fixed to an integer value.
Standard PPP Precise point positioning (PPP) Dual frequency code and carrier phase measurements The precise satellite position and clock determined by network of reference stations and sent to the receiver Integer Ambiguity for the carrier phase measurements cannot be separated from the hardware biases (or uncalibrated phase delays -UPD), and therefore are lumped together as a real valued parameter Integer Ambiguity + HW bias = Float Solution
Standard PPP Approach Precise orbits and clocks GNSS measurements PPP engine Position
PPP with Integer Ambiguity Resolution (IAR) Satellite bias is common for all receivers in a network. Estimate satellite biases using reference station network and supply this to the user. Single differencing using a reference satellite removes receiver biases. Remaining estimated ambiguity has an integer nature. Attempt to fix to the correct integer value for cm-level accuracy. Ability to fix ambiguities to integer value is dependent on observation conditions.
PPP with IAR Map showing location of all reference stations used to calculate the UPD corrections
PPP-IAR Approach Precise orbits and clocks GNSS measurements Troposphere model PPP engine Hardware biases Ambiguities fixed? Yes No Ambiguity fixed position Ambiguity float position
Starfix.G2+ UPD Corrections The corrections the user should use are dependent on their geographic location. There are three regions with global coverage: 1. North and South America 2. Europe, Africa and Middle East 3. Asia and Australia Corrections generated for three large regions provide significantly better results compared to a single global set of corrections. The user does not need to be inside the region in order for the service to work, but should always choose the nearest region.
PPP-IAR Test Results StarPack receivers located at Fugro reference stations. Starfix.G2+ real-time orbit, clock and hardware bias corrections received through L-band link. Identical set-up as used in the field. 95% accuracy of 3.5 cm in horizontal and 8 cm in vertical achieved.
Test results: Bergen, Norway
Test results: Bergen, Norway
Test results: Great Yarmouth, United Kingdom
Test results: Great Yarmouth, United Kingdom
Test results: Houston, Tx, USA
Test results: Houston, TX, USA
Test results: Leidschendam, The Netherlands Interference
Test results: Leidschendam, The Netherlands Interference
Test results: Starfix.G2 vs Starfix.G2+ Values above the Starfix.G2+ bars show the percentage improvement compared to Starfix.G2
Test results: Global Comparison Global distribution of 101 sites Comparison between Starfix.G2 and Starfix.G2+ solutions Comparison of global sites for one day Comparison of one site over 8 days
Global test results: 7 October 2015, 101 sites
Test results: 8 days, Perth, Australia
Test results: 8 days, Istanbul, Turkey
Static results: 8 days, Romoland, CA, USA
Derivation of Tidal Data from GNSS Positioning Systems
GNSS Tides Computations 1 Height Observed GNSS antenna height above ellipsoid CRP height corrected for offset and roll, pitch and heading motion Water level above ellipsoid corrected for heave and draft and smoothing Calm Sea Waves 12 hours Ellipsoid Time
GNSS Tides Computations 2 Height Water level above ellipsoid MSS lookup value is subtracted The difference is the observed tide Calm Sea 12 hours Ellipsoid Time
GNSS Tides Main Components Dual Mode of Operation: Online real time tide computations and logging. Post-processing of logged real time data Multiple Calculations: Multiple MSS Models Available. Multiple Filters Available. Graphic Plots of Filter Performance. Real time NMEA telegram to customer software.
GNSS Tides Filters and Smoothing Filter Modes Raw Data, Real Time and Near Real Time. Filter Types: Spike Detection. Polynomial Fit. Moving Average. Savitzky-Golay Filter. Finite Impulse Filter (FIR). Doodson X0 Filter.
GNSS Tides Overview
GNSS Tides Filter Performance
Summary Fugro is the first company that has offered ambiguity-fixed PPP to the offshore market Our service has been developed throughout the research, development, implementation and testing phases specifically with the offshore market in mind Our results show that we can consistently achieve the stated accuracies of 3.5 cm horizontal and 8 cm vertical