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The Long BaseLine Paragraph
An LBL system comprises a number of acoustic transponders
moored in fixed locations on the seabed. The positions of
the transponders are described in a co-ordinate frame fixed
to the seabed. The distances between them form the 'baselines'
used by the system. The second segment comprises an acoustic
transducer or transceiver which is normally installed on
the vessel, ROV or on a towfish. method provides accurate
positioning over a wide area by measuring ranges from a
vessel to 3 or more transponders deployed at known locations
on the seabed or on a structure. The technique offers a
high degree of positioning repeatability and with range
redundancy, an estimation of the position quality can also
be made.
At the heart of Fusion LBL
is Compatt 5Compatt 5
Faster set up and calibration, greater equipment utilisation
and reduced risk. These are just some of the cost saving
benefits of the latest range of Compatt 5 Wideband transponders
from Sonardyne. . This is Sonardyne’s latest generation
wideband transponder that can be used to create a seabed
navigation network in which targets can be positioned. Crucially,
these networks can offer position accuracies of better than
5cm independent of water depth.
All positioning tasks are
controlled via the Data Fusion Engine a common topside processor
platform that can be used for both LBL and USBL applications.In
practice this means a vessel equipped with a Fusion USBL
transceiver is able to undertake LBL tasks by simply switching
software applications and deploying additional seabed transponders.
Traditionally this would have required the use of separate
and dedicated systems.
This seamless ability to
change roles from say, ROV tracking to construction support,
offers vessel owners and operators unparalleled flexibility.
It also represents a dramatic increase in the performance,
utilisation and therefore, cost effectiveness that can be
expected from acoustic positioning systems.
Fusion LBL supports all
three frequency bands (EHF, MF, LF) within multiple array
configurations. This allows targets to be tracked on any
frequency simultaneously, thereby greatly reducing the problems
associated with acoustic pollution when there are multiple
operations occurring at the same time in the same area.
The system also supports
the use of multiple transceivers or transponders attached
to structures or vehicles to compute heading and attitude
from acoustic observations. A wide variety of sensors can
also be interfaced to a transponder to permit data recovery
by acoustic telemetry. Fusion LBL has been developed to
support all offshore scenarios from large-scale field development
projects through to simple transponder tracking. It is the
total field development solution; a seamless
combination of Software, Firmware and Hardware.
A Typical LBL
System

Illustrated above is a Fusion
system configured for Long BaseLine operations. The equipment
comprises a Data Fusion Engine running Pharos software,
an ROV-mounted .RovNav 5. LBL transceiver and a Compatt
5 seabed transponder array.
If the vessel is already
equipped with a Fusion USBL transceiver, this may be configured
as an LBL transceiver to assist with operations in the Medium
Frequency band.
In common with all of Sonardyne's
latest generation software products, Fusion LBL utilises
a standard Windows User Interface to simplify complex operations
such as array calibration and tracking. This reduces operator
training requirements and saves vessel time by decreasing
the time to first fix.
Features
:-
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Allows multiple targets
to be positioned simultaneously with centimetric precision
independently of water depth
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Operational efficiency
is significantly increased through faster set-up and
faster
array calibration
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Compatible with existing,
worldwide inventories of LBL transponders
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Incorporates Sonardyne's
latest Wideband Technology
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Multiple operating
modes; tone burst and wideband
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Hundreds of operating
channels allowing truly independent acoustic operations
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Easily switch between
USBL and LBL operating modes
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