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wcd ss_v1#1
- 1. Comparison of Wreck Surveying Techniques David Parker UKHO Civil Hydrography Manager
- 2. Acknowledgements RUMP Stephen NIEDERJASPER Marina FUGRO OSAE LAMPE Christian GMBH, Germany SCHUPPAN Alrick VOSS Oliver Gardline Geosurvey, MANN Dave UK SANSOME Ben
- 3. Outline • Requirement for Wreck Surveys • Trial to Compare Available Techniques • Conclusions • Implementation of Water Column Data
- 4. The UK Civil Hydrography Programme • The MCA and UKHO work in Partnership with survey contractors to deliver the CHP • Extensive Coastal and Offshore Waters • Currently £5.4 million p.a. to contractors (plus additional funding through partnering and other sources)
- 7. Outline • Requirement for Wreck Surveys • Trial to Compare Available Techniques • Conclusions • Implementation of Water Column Data
- 8. Requirement for Wreck Surveys • Wrecks present a unique challenge within a hydrographic survey. • Previous UKHO trials have highlighted issues with multibeam depths on wrecks. • Normally a wreck investigation will be undertaken at each wreck site within a larger survey. • Wrecks around the UK are very numerous – one recent CHP survey had over 400.
- 9. Gardline MBES Water Column Trials (2D Cross Section through data)
- 10. Outline • Requirement for Wreck Surveys • Trial to Compare Available Techniques • Conclusions • Implementation of Water Column Data
- 11. Wreck Investigation Trials • In Nov / Dec 2010, a field trial was undertaken with Fugro OSAE to compare the least depth over wrecks obtained from: – Wire Sweep – Multibeam conventional bottom detect – Side Scan Sonar – MBES Water Column Data
- 12. MV Meridian
- 19. Height of feature above seabed was measured
- 23. MBES WCD Results SSS Wire sweep Difference from least depth least depth least depth cleared depth Next Shoalest [m] [m] [m] [m] [m] 28.6 28.6 28.6 - 0.0 36.0 35.9 36.0 - 0.1 30.3 30.1 30.3 - 0.2 29.6 29.6 29.6 - 0.0 38.2 38.0 38.2 - 0.2 35.6 35.6 35.3 - 0.3 31.6 31.8 31.8 - 0.2 20.3 20.4 20.8 - 0.1 34.3 32.6 34.3 - 1.7 32.3 32.2 32.3 - 0.2 27.4 24.8 27.3 - 2.6 30.2 30.2 30.2 - 0.0 27.1 27.8 26.6 27.3 0.5 30.0 30.0 30.0 29.5 0.5 35.4 35.7 35.9 34.9 0.5 35.9 35.8 36.0 35.4 0.1 18.8* 15.2 - 15.6 0.3
- 24. Conclusions 1 • The “real time” bottom detect from a MBES will not necessarily give the shallowest depth within the beam. • SSS can give valuable extra information about wrecks, but this requires a towfish. • Wire sweeping is difficult and time consuming, and can be unreliable.
- 25. Conclusions 2 • Wire sweeping limited by fishing gear and traffic, and presents risk to the survey ship. • MBES WCD appears to provide reliable information which the MBES alone may miss. • WCD resolution is normally comparable to a good SSS, but quicker and easier to gather.
- 26. Conclusions 3 • Collecting WCD over wrecks takes on average 5% of the time that a wire sweep may take. • Collecting WCD over wrecks takes on average 30% of the time collecting SSS takes. • Costs and risks are considerably reduced. • Results WCD are at least as reliable as previous methods.
- 27. Outline • Requirement for Wreck Surveys • Trial to Compare Available Techniques • Conclusions • Implementation of Water Column Data
- 28. Implementation • The requirement for WCD has been introduced to the CHP specification. • Images or animations used to support the designation of least depth. • Care needs to be taken with respect to; – minimum slant range echo, – multiple transmit sectors – Other acoustic interference etc.
- 30. Current WCD Software • The tools for analysing and utilising WCD are fairly new, and will improve with time. • FM Midwater tools available now. • Echoview Software Currently available, but oriented towards fisheries applications. • CARIS introduced their WCD tool with CARIS HIPS v7.1 Service Pack 1 in Jan 2012 – UKHO gave some assistance.
- 31. Echoview using MBES WCD for Biomass Estimate
- 32. CARIS HIPS 11m
- 33. MBES Firmware Development • It may be advantageous if the advanced user could select an alternative bottom detect algorithm. • “normal” for standard seabed mapping (clean data) • “first valid return in beam” for activities such as wreck investigations. • Even better – multiple detects within each beam - save on disk space and data management issues
Editor's Notes
- Why? The MCA has overall responsibility for the UK’s obligations under SOLAS – including Chapter 5, regulation 9. We have no other drivers apart from Safety of Life At Sea. We can react quickly. We are good at it. We can demonstrate that we offer the best value for money to the government. Where? 723,181km2 of seabed How Much Do We Spend? The MCA procure around £5.4m of hydrographic services every year in order to help keep UK charts and publications up to date. Data is given to the UKHO free of charge in order to update nautical charts and publications