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

THALES GEOSOLUTIONS PACIFIC 2/28 TGPI 11/2003 Objective: Enable precise timing and TrueHeave 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

THALES GEOSOLUTIONS PACIFIC 3/28 TGPI 11/2003 Why is Timing Important? 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

THALES GEOSOLUTIONS PACIFIC 4/28 TGPI 11/2003 Precise Timing—Selecting an Epoch 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

THALES GEOSOLUTIONS PACIFIC 5/28 TGPI 11/2003 Supported Sub-Systems 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.

THALES GEOSOLUTIONS PACIFIC 6/28 TGPI 11/2003 System Topology

THALES GEOSOLUTIONS PACIFIC 7/28 TGPI 11/2003 XTF Packets were created to hold the new time stamps

THALES GEOSOLUTIONS PACIFIC 8/28 TGPI 11/2003 Precise Timing & TrueHeave Acquisition 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

THALES GEOSOLUTIONS PACIFIC 9/28 TGPI 11/2003 Precise Timing & TrueHeave Processing 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

THALES GEOSOLUTIONS PACIFIC 10/28 TGPI 11/2003 Modified Patch Test Procedures 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

THALES GEOSOLUTIONS PACIFIC 11/28 TGPI 11/2003 Roll Timing Error in Caris Subset Mode (simulated data)

THALES GEOSOLUTIONS PACIFIC 12/28 TGPI 11/2003 Roll Timing Error in Caris Subset Mode (real data)

THALES GEOSOLUTIONS PACIFIC 13/28 TGPI 11/2003 Roll Timing Error Removed

THALES GEOSOLUTIONS PACIFIC 14/28 TGPI 11/2003 Multiple Lines with Roll Timing Error

THALES GEOSOLUTIONS PACIFIC 15/28 TGPI 11/2003 Multiple Lines with Roll Timing Error Removed

THALES GEOSOLUTIONS PACIFIC 16/28 TGPI 11/2003 TrueHeave: What is it? Without interrupting the flow of the real time heave 1. Unfiltered heave data is stored in the POS/MV memory 2. After a few minutes, a zero phase filter is passed over the stored heave data 3. The delayed heave value and real time heave value are output together over the Ethernet Output Times Heave values Valid Times

THALES GEOSOLUTIONS PACIFIC 17/28 TGPI 11/2003 TrueHeave Processing 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.

THALES GEOSOLUTIONS PACIFIC 18/28 TGPI 11/2003 Real Time Heave v. TrueHeave Meters Seconds True Heave Real Time Heave

THALES GEOSOLUTIONS PACIFIC 19/28 TGPI 11/2003 Real Time Heave (3x) TrueHeave (3x)

THALES GEOSOLUTIONS PACIFIC 20/28 TGPI 11/2003 Real Time Heave TrueHeave

THALES GEOSOLUTIONS PACIFIC 21/28 TGPI 11/2003 How TrueHeave Affects Run-In Time Real Time Heave Applied TrueHeave Applied

THALES GEOSOLUTIONS PACIFIC 22/28 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 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 South Yakutat 372 sq km Pamplona Spur 162 sq km Kenai Fjords 535 sq km Chirikof Island 1488 sq km Fairweather 219 sq km Cape Hinchenbrook 1830 sq km

THALES GEOSOLUTIONS PACIFIC 23/28 TGPI 11/2003 Data Samples: Alaska Surveys Castle Bay

THALES GEOSOLUTIONS PACIFIC 24/28 TGPI 11/2003 Sun Illuminated Bathymetry 3x Vertical Exaggeration 3m bins, 4m – 50m depths

THALES GEOSOLUTIONS PACIFIC 25/28 TGPI 11/2003 Sun Illuminated Bathymetry 3x Vertical Exaggeration 3m bins, 4m – 50m depths

THALES GEOSOLUTIONS PACIFIC 26/28 TGPI 11/2003 Precise Timing Benefits 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.

THALES GEOSOLUTIONS PACIFIC 27/28 TGPI 11/2003 TrueHeave Benefits 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 min Lines Total turn time hrs (at 5 min) = 4.5 days Time saved on turns: 4.5 days

THALES GEOSOLUTIONS PACIFIC 28/28 TGPI 11/2003 Acknowledgments: 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