Real-time tidal observation is possible using high-accuracy GPS positioning systems. VERIPOS has implemented this using their Ultra PPP system, which provides 10-20cm vertical accuracy. This allows correlation between GPS heights and tides after removing vessel motion effects. Two tidal estimates are provided - an "Ultra Tide" after 39 hours of averaging, and an instantaneous "Geoid Tide" based on the EGM96 geoid model. VERIPOS tidal estimates have been validated against predicted tides and tide gauges with standard deviations of 10-13cm. The method provides benefits over traditional tide gauges for applications like bathymetry and current prediction.

1. Real-time Tidal Observation using High-Accuracy GPS Positioning Pieter Toor Research & Development Manager VERIPOS Hydrographic Society Benelux, Dordrecht 7 th May 2008

3. Corporate Structure Subsea 7 Inc. Construction / IRM VERIPOS i-Tech Drill Rig Support Oslo S.E.

14. Ultra Tide vs. Geoid Tide 39 HOURS 1010010110201102112 0 2112011020110100101/30 Geoid Tide Ultra Tide = Avg. Ultra Height – Doodson X0 output Geoid Tide = Avg. Ultra Height – EGM96 (Earth Gravitational Model 1996) Tide Value Availability Ultra Tide Start of Ultra positioning 39 hours

18. Comparison Against Tide Gauge

19. Comparison Against Tide Gauge

20. Comparison Against Tide Gauge

22. Validation on Subsea Vessel Results highlight biases in EGM96 Geoid Model (accurate to +/- 1m)

26. Positioning for Success Thank you for your attention ? QUESTIONS