Advances in GNSS Technology and it s Application to Tidal Derivation

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2 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

3 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

4 Transit system first used High frequency DGPS service HP dual-frequency service Starfix positioning system Satellite based DGPS 4

5 XP precise point positioning (PPP) service G4 multi-constellation PPP service G2 GPS & GLONASS PPP service G2+ ambiguity-fixed PPP service 5

6 Latest GNSS Developments within Fugro

7 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

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9 Starfix.G2 - DataFlow

10 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

11 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.

12 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

13 Standard PPP Approach Precise orbits and clocks GNSS measurements PPP engine Position

14 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.

15 PPP with IAR Map showing location of all reference stations used to calculate the UPD corrections

16 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

17 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.

18 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.

19 Test results: Bergen, Norway

20 Test results: Bergen, Norway

21 Test results: Great Yarmouth, United Kingdom

22 Test results: Great Yarmouth, United Kingdom

23 Test results: Houston, Tx, USA

24 Test results: Houston, TX, USA

25 Test results: Leidschendam, The Netherlands Interference

26 Test results: Leidschendam, The Netherlands Interference

27 Test results: Starfix.G2 vs Starfix.G2+ Values above the Starfix.G2+ bars show the percentage improvement compared to Starfix.G2

28 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

29 Global test results: 7 October 2015, 101 sites

30 Test results: 8 days, Perth, Australia

31 Test results: 8 days, Istanbul, Turkey

32 Static results: 8 days, Romoland, CA, USA

33 Derivation of Tidal Data from GNSS Positioning Systems

34 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

35 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

36 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.

37 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.

38 GNSS Tides Overview

39 GNSS Tides Filter Performance

40 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