Precise Timing and TrueHeave ® in Multibeam Acquisition and Processing

1. TGPI 11/2003 Precise Timing and TrueHeave® in Multibeam Acquisition and Processing Doug Lockhart, Thales GeoSolutions (Pacific) Inc Dushan Arumugam, Thales GeoSolutions (Pacific) Inc

2. TGPI 11/2003 Timing overview: Why timing is important Precise timing Selecting an epoch Supported Sub-Systems System topology Modified patch test procedures TrueHeave acquisition and processing Timing and TrueHeave economic benefits Objective: Enable precise timing and TrueHeave

3. TGPI 11/2003 Multibeam Bathymetry is created from a number of data elements Sounder ranges and angles Position Pitch, Roll, Heave Heading Data elements are merged using time as a common index Timing errors and variable latencies will result in a miss match or irregular merge of the data elements The bad merge will produce a sounding calculation that is both horizontally and vertically inaccurate Why is Timing Important?

4. TGPI 11/2003 Time stamp data when it is created, not when it is logged. Select a standard epoch. PC millisecond timers define their own epoch and are not standard Use a single clock/epoch to time stamp all data. Position, attitude, and heading are time stamped in the POSMV on the UTC epoch TrueHeave data can be time stamped by the POSMV on the UTC or GPS time Precise Timing—Selecting an Epoch

5. TGPI 11/2003 Precise Timing and TrueHeave have been implemented on the following systems by TGPI: Reson SeaBat Applanix POS/MV TritonElics ISIS (XTF) Caris HIPS Other implementations are possible. Supported Sub-Systems

6. TGPI 11/2003 System Topology

7. TGPI 11/2003 XTF Packets were created to hold the new time stamps

8. TGPI 11/2003 Logged in XTF by TEI ISIS Position, Heading and Attitude data time stamped in POS/MV on UTC epoch Bathy data Time Stamped in SeaBat using POSMV UTC serial string Logged by POS/MV Controller TrueHeave data time stamped within the POS/MV on UTC epoch TrueHeave data is logged throughout the survey day, independent of line changes Precise Timing & TrueHeave Acquisition

9. TGPI 11/2003 XTF files are converted into HDCS format by Caris Options in the XTF converter let the user selected the XTF packets containing the new timing Precise Timing & TrueHeave Processing

10. TGPI 11/2003 Acquisition Line pairs for Pitch, Roll and Yaw are required Pitch, Roll and Yaw lines are processed as usual Navigation Latency lines are not required Navigation latency can be determined from any single line Processing Pitch, Roll and Yaw are processed as usual Navigation latency is determined by examining roll timing error Roll timing error is negated and applied to the ping time, accounting for all navigation and attitude latencies Modified Patch Test Procedures

11. TGPI 11/2003 Roll Timing Error in Caris Subset Mode (simulated data)

12. TGPI 11/2003 Roll Timing Error in Caris Subset Mode (real data)

13. TGPI 11/2003 Roll Timing Error Removed

14. TGPI 11/2003 Multiple Lines with Roll Timing Error

15. TGPI 11/2003 Multiple Lines with Roll Timing Error Removed

16. TGPI 11/2003 Without interrupting the flow of the real time heave Unfiltered heave data is stored in the POS/MV memory After a few minutes, a zero phase filter is passed over the stored heave data The delayed heave value and real time heave value are output together over the Ethernet TrueHeave: What is it? Heave values Output Times Valid Times

17. TGPI 11/2003 Caris allows the user to browse and select raw POS/MV files containing TrueHeave data. The heave record in the HDCS format can be replaced with the TrueHeave or real time heave record. TrueHeave Processing

18. TGPI 11/2003 Seconds True Heave Real Time Heave Real Time Heave v. TrueHeave Meters

19. TGPI 11/2003 Real Time Heave (3x) TrueHeave (3x)

20. TGPI 11/2003 Real Time HeaveTrueHeave

21. TGPI 11/2003 TrueHeave Applied Real Time Heave Applied How TrueHeave Affects Run-In Time

22. TGPI 11/2003 Cook Inlet 556 sq km Portlock Bank 850 sq km Albatross Bank 27 sq km Castle Bay 207 sq km Semidi Islands 2875 sq km UNCLOS 17160 sq km Pribilof Islands 38 sq km UNCLOS 9194 sq km Icy Bay 305 sq km Yakutat Bay 36 sq km Glacier Bay 425 sq km Northern Clarence Strait 290 sq km Cape Ommaney 280 sq km Hazy Islands 395 sq km Aleutian Islands 2362 sq km Cape Hinchenbrook 1830 sq km Chirikof Island 1488 sq km Kenai Fjords 535 sq km Pamplona Spur 162 sq km South Yakutat 372 sq km Fairweather 219 sq km

23. TGPI 11/2003 Data Samples: Alaska SurveysCastle Bay

24. TGPI 11/2003 Sun Illuminated Bathymetry3x Vertical Exaggeration3m bins, 4m – 50m depths

25. TGPI 11/2003 Sun Illuminated Bathymetry3x Vertical Exaggeration3m bins, 4m – 50m depths

26. TGPI 11/2003 Reducing timing errors results in more room in the error budget for other errors such as Tides & SVP Mechanically induced artifacts are easier to diagnose when timing errors are small Increased operational weather window. No survey time was lost due to excessive vessel motion in Alaska this summer. Precise Timing Benefits

27. TGPI 11/2003 Reduced heave component in error budget, particularly during long period swell Shorter turn times, line changes, and easier shoreline surveys Realized savings from a single survey Prince William Sound Estimate turn times for real time heave filter - 10 min Actual turn time - 4-5 min Lines - 1293 Total turn time - 107.75 hrs (at 5 min) = 4.5 days Time saved on turns: 4.5 days TrueHeave Benefits

28. TGPI 11/2003 NOAA:Our existing large Alaska survey contract allows us to invest internally on R&D efforts like this that ultimately benefit our operations, NOAA and the hydrographic community. Applanix:Rob Corcoran implemented TrueHeave in the POS/MV and provided valuable technical assistance TritonElics Inc & Caris:Software providers made quick updates to their software to support the new timing and TrueHeave Acknowledgments: