Underwater Technology Vol 27 No 1
Winter 2007
A
Personal View
Some inconvenient truths
Author
Technical
Papers
Underwater technology and international patent
strategies from a US perspective
W Buskop
Abstract:
Inventions for underwater technology can include a
variety of new subsea innovations, such as methods for placing moorings,
manufacturing of hyrophones, using remotely operated vehicles (ROV) in a new
way, a new lighting device to illuminate underwater drilling, underwater test
equipment, controls systems, quick disconnects and fancy new diving flippers.
Protecting this technology in the United States, and internationally in the
countries of the 134 members of the Patent Cooperation Treaty (PCT), is an
expensive and sometimes seemingly endless process.
Decoupled modelling and controller design for the
hybrid autonomous underwater vehicle: MACO
J Kennedy, E Gamroth, C Bradley, and AA Proctor
Abstract:
Researchers at the University of Victoria have
developed a hybrid autonomous underwater vehicle (AUV) named MACO capable of
three-dimensional keeping and manoeuvring without forward velocity. This makes
it suitable to perform many of the tasks traditionally accomplished by remotely
piloted underwater vehicles. Once operational, MACO was used in a Defence
Research and Development Canada (DRDC) feasibility study for using AUVs to
support rapid deployment of acoustic element arrays. The AUV was required to
stop and hover, while triggering a low frequency sound source. The performance
of the MACO during these sea trials is presented as the conclusion to this
paper.
A determination of the propagation of
electromagnetic waves through seawater
J Lucas and CK Yip
Abstract:
For the past four years detailed experiments have
been carried out to investigate the propagation of electromagnetic (EM) waves
between antennae in seawater in the MHz frequency range. The results have
clearly shown that propagation is possible over a distance of 100m in a
Liverpool Dock for frequencies in the range 1 to 5MHz using a 30W amplifier. The
existing water/air/water model of propagation cannot explain this result.
Therefore a theoretical model is given in this paper to explain the result and
to give a generalised solution. It is based upon the generation of EM waves by
dipole oscillations of the water molecules within the antenna electric field.
The model has explained all the features observed in detailed experimental
results obtained in tank experiments with both tap and salt water, whose
conductivity varies between 0.1 and 4S/m, as well as in trials within Liverpool
Dock. Within the tank the received signal in tap water increases with increasing
frequency, whilst in salt water it decreases with increasing signal frequency.
In general the signals in seawater are –55dB lower than in tap water. For each
frequency the signal strength in seawater during propagation shows a rapid
decrease in the vicinity of the transmitting antennae (near field) but only
shows a slow decrease in the far field. The slow decay in the far field is
attributed to a combined diffraction loss and an attenuation loss that increases
with frequency. The result in the received signal exhibits a resonant effect in
the frequency range 10 to 20MHz for propagation in seawater for a distance of
100m. Lower and higher MHz frequencies are difficult to propagate because the
received signal strength is comparable with the background electrical noise
within seawater (–135dBm) when a 30W signal is transmitted.
Meeting
Reports
Selected Summary Highlights from the 54th Meeting
for IMO's Marine Environment Protection Committee (MEPC 54), 20–24 March 2006
P Verlaan
Selected Summary Highlights from the 28th
Consultative Meeting (LC 28) of Contracting Parties to the Convention on the
Prevention of Marine Pollution by Dumping of Wates and Other Matter 1972 (London
Convention 1972) and the 1st Meeting of Contracting Parties to the 1996 London
Protocol (LP 1) to the London Convention (London Protocol: LP) 20 October–3
November 2006 in London
P Verlaan
Book
Review
Homo Britannicus; the incredible story of human
life in Britain by Chris Stringer
Review by N Flemming
Underwater Technology Vol 27 No 2
Winter 2007
A
Personal View
Forty Years of SUT
I Gallett
Technical
Papers
Insurance for autonomous underwater vehicles
G Griffiths, N Bose, J Ferguson, DR Blidberg
Abstract:
The background and practice of insurance for
autonomous underwater vehicles (AUVs) are examined. Key topics include:
relationships between clients, brokers and underwriters; contract wording to
provide appropriate coverage; and actions to take when an incident occurs.
Factors that affect cost of insurance are discussed, including level of
autonomy, team experience and operating environment. Four case studies from
industry and academia illustrate how AUV insurance has worked in practice. The
paper concludes by stressing the importance of effective dialogue between
client, broker and underwriter to review, assess and reduce risk to the benefit
of all parties.
The influence of energy extraction from open channel
flow and its impact on tidal current energy system design
JP Chick, IG Byrden and SJ Couch
Abstract:
This paper explores the sensitivity of a simple
model of open flows, which has been developed to facilitate the preliminary
assessment of the suitability of tidal channels for energy exploitation. Using
models deliberately simplified for clarity, the sensitivity is shown to be
dependent primarily upon length, depth and boundary roughness. The model results
are then used to support the use of a non-dimensional number which may prove
useful in future classification of the sensitivity of tidal channels. Energy
extraction from a tidal stream is shown to have the potential for significantly
altering the flow through the channel in question and, in doing so, imposes
constraints on the design of the extraction system itself. This differs
significantly from the practice of resource assessment in the wind energy
industry.
Automatic seabed texture segmentation and
classification based on wavelet transform and fuzzy approach
R Javidan and HJ Eghbali
Abstract:
This paper deals with segmentation and
classification of textual images of seabed using wavelet domain features and
modified split and merge algorithm based on fuzzy approach. The original image
is first analysed using a fuzzy edge detector to improve the differentiation
between different texture types. Simultaneously, two-level standard wavelet
transform is applied to the original image. The high frequency detail
coefficients produced from the six sub-bands of the wavelet and the image
produced by the fuzzy edge detector are divided into M x M blocks.
Energy of each block is calculated and a minimum distance classifier is used for
each wavelet and fuzzy block to classify (and segment) the original image in a
hierarchy of three levels of resolutions. The classified blocks of the two
segmented images produced by the wavelet transform are merged and refined based
on degree of edge certainty acquired form the fuzzy algorithm to construct the
final segmented image. In this research, it is shown that energies of the
wavelet coefficients are powerful features for discrimination of different
seabed textures. The classification results of the energy features of the
wavelet coefficients are compared with the results of other features of the
wavelet coefficients to show the fidelity of this feature. The proposed approach
provides a fast tool with enough accuracy that can be applied in real-time
applications of automatic discrimination of the seabed. Moreover, the simulation
results are compared with other well-known methods to show the effectiveness of
the proposed algorithm.
Meeting
Report
Selected Summary Highlights from the 55th Meeting of
the intergovernmental Marine Environment Protection Committee (MEPC 55) of the
International Maritime Organisation (IMO), 913 October 2006, held at Central
Hall Westminster, London
P Velaan
Book
Review
Lost Treasure Ships of the Northern Seas: A Guide
and Gazetteer to 2000 Years of Shipwreck by Nigel Pickford
Reviewed by R Rogers
Underwater Technology Vol 27 No 3
Scientific and
Archaeological Diving Special Issue
Autumn/Winter 2007
A
Personal View
The past,
present and future for scientific diving
MDJ Sayer
Technical
Papers
Scientific
diving: bibliographic analysis of underwater research supported by SCUBA diving
1995
–2006
MDJ Sayer
Abstract:
There is little quantitative information by which to assess the recent
importance of diving to the scientific community. This review is a bibliographic
analysis of the papers published from 1995 to 2006 that have been supported by
scientific diving. Diving supports scientific research through efficient and
targeted sampling (including numerous new species and reports), quantitative
survey, observing animal behaviour, making in situ measurements,
undertaking impact studies, a variety of ecological analyses, the evaluation of
new techniques, by mapping underwater areas, profiling subtidal geology and by
deploying and retrieving underwater apparatus. Each section is reviewed in
detail. However, by comparing the database searches against a selection of
publications known to have used scientific diving in the same period, possibly
only 7% (with 96% confidence limits of 0-15%) od papers were captured. It is
suggested that the significance of scientific diving is vastly unrepresented by
the literature and that the divers themselves should try to ensure proper
acknowledgment in order to preserve and promote scientific diving as a valid and
cost effective underwater research tool.
Scientific
diving in the United States: the value of SCUBA as research methodology
M Lang
Abstract:
The US scientific diving regulatory, medical,
training and operational framework has resulted in a remarkably low
decompression sickness incidence rate. In this particular segment of the diving
community, diving safety research on dive computers, ascent rates, multi-day
repetitive diving, polar diving, reverse dive profiles, oxygen-enriched air and
advanced scientific diving contributes to the conservative risk management
approach of scientific diving. The importance of scientific diving as a valuable
research tool by placing the trained scientist's eye under water is illustrated
by a number of Smithsonian Institution research projects that could otherwise
not have been performed, with results published in the scientific literature.
The peer-review publication process validates the viability and effectiveness of
SCUBA as a research methodology.
The
investigation of submerged Stone Age Landscapes using diving as a research tool:
an example from Denmark
O Grøn
Abstract:
Diving offers a research tool that permits access to well-preserved submerged
sites of highly significant archaeological and cultural interest. As an example,
this account presents a summary of an excavation of a dwelling and a grave at a
submerged 7000-year-old Danish Stone Age site and discusses the implications of
the presence of extremely well preserved Stone Age sites and entire Stone Age
landscapes under water. Submerged Stone Age sites may yield a wealth of
archaeological information because of the quality of preservation and the
relative lack of disturbance. Diving presents an effective tool for unlocking
the secrets of these sites.
Use of
diving computers in brittlestar surveys
KJ Collins
and B Baldock
Abstract:
Dense beds of brittlestars (Ophiothrix fragilis) were
discovered in 1975 in water depths of 10-20m off Broad Beach,
Kimmeridge, Dorset, within the Purbeck Marine Wildlife Reserve.
Drift dives carried out during 2001–2003
aimed to map the extent of these aggregations. This paper describes
the methods employed: tracking drift drives with GPS positions of
the dives surface marker buoys in combination with sport diving
computers recording time and depth plus 'events' (ie, the start and
end of aggregations). The combination of GPS and dive computer
enabled mapping of these aggregations in three dimensions. The
brittlestars were found to be associated with the upper slopes of
reef ridges but absent from the summit and troughs. Application of
the techniques to biogenic worm reef (Sabellaria spinulosa)
and maerl (Phymatolithon calcareum) surveys are described.
The
influence of census technique on estimating indices of macrofaunal population
density in the temperate rocky subtidal zone
MDJ Sayer
and C Poonian
Abstract:
Several studies have attempted to compare subtidal animal population
estimates obtained in a variety of ways using SCUBA diving and have
reported a lot of variations between the estimates obtained. This
study investigated individually scale-, tidal-, equipment- and
observer-induced variation through analysis of animal population
density indices obtained using a number of techniques based on SCUBA
diver visual survey. The study was based on shallow subtidal sites
on the west coast of Scotland including natural rocky slopes and
recently deployed artificial reef sites. Groups of species
investigated varied in levels of size, abundance, mobility and
detectability. Variability in estimated densities between different
sizes of sampling unit, state of tide, type of SCUBA equipment used
(open circuit versus rebreather) and observation technique was found
to be considerable. A decreasing asymptotic relationship with
quadrant size was evident in the majority of cases for estimated
density, coefficient of variation and number of samples required to
attain a given precision. However, the size of the sampling unit
employed had to be large enough to encompass the variability
in spatial distribution of the target organism. Improved precision
for estimates of cryptic species was obtained from relatively small
sampling units, which focused the observer's attention onto a
specific area. Underwater photography as a population estimation
technique produced data comparable with that from visual surveys but
was limited by the size of the sampling unit. The use of remotely
deployed infrared video demonstrated that certain animal species and
life-stages actively avoid divers and were largely absent from the
diver-based surveys. Although larger quadrants generated more
precise estimates, the longer sampling times involved reduced their
overall efficiency for most groups surveyed; optimum sampling unit
sizes are suggested for particular animal groups.
Tech Briefing
The use of
archaeological diving, survey and literature-based techniques to evaluate
potential protected status for shipwrecks
DM
McElvogue
Abstract:
Unlike military aircraft, shipwrecks do not automatically gain
protected status under the 1986 Protection of Military Remains Act.
Irrespective if whether or not there was any loss of life or whether
the wrecking occurred during peacetime or in combat, the
determination of protected status for shipwrecks, commonly referred
to as designated war graves, usually depends on a judicial review
process. Where there is no good historical evidence to support the
case for protection, the determination of status may then be based
on information obtained from present-day surveys. This technical
note gives an overview of how archaeological survey methodologies
can be employed in attempting to provide evidence to support, or
otherwise, a claim form protected status. This account is based on
the example of the SS Storaa.
Book
Review
The
Profession Diver;s Handbook, Second Edition
–
by John Bevan PhD
Reviewed by DR Shiers
Underwater Technology Vol 27 No 4
Oceanography International Special Issue
Spring/Summer 2008
A Personal View
The threat and promise of methane
hydrates
D Hazelwood
Technical Papers
The progression and impact of the
latest generation of multibeam acoustics upon multidisciplinary
hydrographic-based applications
C Malzone, D Lockhart, T Meurling and
M Baldwin
Abstract:
The progression of hydrographic echo
sounding has been driven by navigational, socioeconomic (EEZ, Law of
the Sea, Offshore Oil/Gas) and research (habitat mapping, coastal
erosion, etc) requirements. Since the first installation of a
multibeam echo sounder (MBES) in 1963, the progression of the
technology has provided a steady increase in the number of
soundings, as well as increases in sampling rates, data volumes and
system resolution. Recent improvements incorporate better
signal-to-noise ratios, multiple frequencies, calibrated arrays and
new signal processing functionality. These advancements, combined
with parallel improvements in data acquisition methods and
post-processing techniques, make the data more accurate, thus
providing more reliable survey products. MBES technology now makes
use of all aspects of the inherent acoustics to provide additional
data products, such as beam intensity, pseudo-sidescan, seafloor
backscatter and raw time series backscatter. The latest generation
of MBES now contains the processing power to log concurrently all
datagrams with the same sampling and ping rates as the International
Hydrographic Organization (IHO) Special Order bathymetry data
(34.5kHz and 40Hz, respectively). The result has been the
incorporation of multibeam derived products for multidisciplinary
hydrographic-based applications, such as nautical charting, habitat
mapping, fisheries biomass surveys and sediment transport studies.
This paper explores recent improvements in MBES systems in
comparison with their older counterparts and discusses the effects
these advancements will have on the future of multidisciplinary
hydrographic-based applications in both shallow and deep waters.
Technical Papers
Environmental impact and appraisal -
planning consent for the South West of England Wave Hub
N Harrington and I Andina-Pendás
Abstract:
Wave Hub is an innovative demonstration
site for generation of wave energy located in the South West of
England. In simple terms, Wave Hub consists of an offshore
electrical 'socket' to connect arrays of wave energy converters to
the national grid via undersea cables, allowing technology
developers to demonstrate and monitor the operation of their devices
in real sea conditions. A key element in the development of the
proposed Wave Hub was to gain consent from the relevant UK
regulatory bodies. This paper describes the process for the consent
application followed and highlights the main issues encountered
during the preparation of the environmental studies to support the
application, and subsequent discussions with regulators and
stakeholders.
Technical Papers
Improved measurement technologies for
floating wave energy converter (WEC) mooring arrangements
L Johanning and GH Smith
Abstract:
Large-scale experiments were conducted
under real sea conditions to support the investigation of non-linear
mooring line effects and their importance to moored wave energy
device installations. The problems associated with such testing are
described, and a discussion of solutions to overcome these is given.
An improvement of the experimental apparatus and procedures resulted
in meaningful data that could be compared with tank testing and
numerical models. The lessons learned have provided confidence in
the future implementation of an offshore mooring test facility off
the Cornwall coast.
Technical Papers
Synthetic aperture 3D buried object
imaging
S Schock
Abstract:
A towed synthetic aperture sonar called
buried object scanning sonar (BOSS) performs synthetic aperture
processing and generates orthogonal projections of 3D subsurface
data to view objects buried in the seabed. The development of BOSS
is reviewed, including significant results. During an experiment in
St Andrews Bay, Florida, the latest version of BOSS, called
BOSS-160, generated images of small cylinders (simulating ordnance)
buried at two shallow water sites with 3m water depths, and with
sand and muddy sand bottom types. Image projections show the
orientation, length and burial depth of cylinders with diameters of
5, 7.5, 10 and 15cm.
Technical Papers
The role of autonomous underwater
vehicles for marine search and rescue operations
AJ Murphy, MJ Landamore and RW
Birmingham
Abstract:
There is an ever-increasing adoption of
new technologies to improve safety of life, and autonomous
technology is no exception. The use of robotic machines for
assisting in search and rescue (SAR) operations is evident in land
and air based scenarios, and European calls for research into the
use of remotely operated or autonomous systems specifically address
this requirement for marine based search and rescue. This paper
addresses the current state of autonomy in the search and rescue
field, as well as the current technologies available for marine
applications. A concept for using autonomous underwater vehicles (AUVs)
in marine search roles for SAR scenarios is provided, and the
feasibility of such a system is demonstrated. Existing commercially
available AUVs are shown to be capable of providing a viable search
area coverage rate, and sensor technology is sufficiently mature to
enable detection of survivors from the proposed autonomous platform.
The technical challenges for further development of the concept are
also addressed.
Technical Papers
The role of autonomous underwater
vehicles for marine search and rescue operations
AJ Murphy, MJ Landamore and RW
Birmingham
Abstract:
There is an ever-increasing adoption of
new technologies to improve safety of life, and autonomous
technology is no exception. The use of robotic machines for
assisting in search and rescue (SAR) operations is evident in land
and air based scenarios, and European calls for research into the
use of remotely operated or autonomous systems specifically address
this requirement for marine based search and rescue. This paper
addresses the current state of autonomy in the search and rescue
field, as well as the current technologies available for marine
applications. A concept for using autonomous underwater vehicles (AUVs)
in marine search roles for SAR scenarios is provided, and the
feasibility of such a system is demonstrated. Existing commercially
available AUVs are shown to be capable of providing a viable search
area coverage rate, and sensor technology is sufficiently mature to
enable detection of survivors from the proposed autonomous platform.
The technical challenges for further development of the concept are
also addressed.
Technical Papers
Development and field testing of the
Doppler Volume Sampler
PE Plimpton and JW Mullison
Abstract:
In 2004 the Pacific Marine Environmental
Laboratory (PMEL) sponsored a Request for Proposals (RFP) from
industry to develop a new instrument that combined ocean current
measurements, highly accurate temperature measurements and inductive
communication in a single package. To support global ocean
monitoring, the new instruments would be deployed on PMEL's deep
ocean surface moorings at selected depths from the near surface to
750m, with data telemetered to shore via satellite in near real
time. From the proposals submitted, PMEL selected the Doppler Volume
Sampler (DVS), a point current meter developed by Teledyne RD
Instruments, for testing. This paper discusses the DVS engineering
design, measurement capabilities, including features for data
quality assessment, and the testing performed during the instrument
evaluation.
Meeting Report
Subscribed Content Selected
Highlights of the 29th Consultative Meeting (LC 29) of Contracting
Parties to the Convention on the Prevention of Marine Pollution by
Dumping of Wastes and Other Matter 1972 (London Convention 1972) and
the 2nd Meeting of Contracting Parties to the 1996 London Protocol
(LP 2) to the London Convention (London Protocol; LP), held at the
Headquarters of the International Coffee Organization, 5-9 November
2007 in London
P Verlaan
Book Review
Admiralty Salvage in Peace & War
1906–2006: 'Grope, Grube and Tremble'
–
by Tony Booth
Reviewed by J Bevan
