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.
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
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.
29.
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.
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
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
