Loading in 2 Seconds...
Loading in 2 Seconds...
Precise Timing and TrueHeave ® in Multibeam Acquisition and Processing. Doug Lockhart, Thales GeoSolutions (Pacific) Inc Dushan Arumugam, Thales GeoSolutions (Pacific) Inc. Timing overview: Why timing is important Precise timing Selecting an epoch Supported Sub-Systems System topology
Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
Doug Lockhart, Thales GeoSolutions (Pacific) Inc
Dushan Arumugam, Thales GeoSolutions (Pacific) Inc
Multibeam Bathymetry is created from a number of data elements
Sounder ranges and angles
Pitch, Roll, Heave
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 inaccurateWhy is Timing Important?
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 timePrecise Timing—Selecting an Epoch
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 changesPrecise Timing & TrueHeave 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
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 latenciesModified Patch Test Procedures
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 EthernetTrueHeave: What is it?
556 sq km
850 sq km
27 sq km
207 sq km
2875 sq km
17160 sq km
38 sq km
9194 sq km
305 sq km
36 sq km
425 sq km
Northern Clarence Strait
290 sq km
280 sq km
395 sq km
2362 sq km
1830 sq km
1488 sq km
535 sq km
162 sq km
372 sq km
219 sq km
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
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 daysTrueHeave Benefits
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 TrueHeaveAcknowledgments: