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APPLICATION NOTE:
MS 1000/SCANNING SONAR: DIVER POSITIONING/SUPPORT
Introduction:
Anyone who has worked underwater - either as a diver or Remotely Operated Vehicle (ROV) pilot
- understands the frustration of not knowing precisely where they are with respect to objects
around them. To the unfamiliar observer, the process of sub-sea navigation appears to be simple;
we have all seen the documentaries and that clear, blue, Caribbean water.
The reality of working in the commercial diving or ROV business is that you are rarely able to see
more than a metre or two. More often than not, a diver will be in zero visibility where sensory input
is limited only to touch. It seems impossible, but there are times a diver can shine a light into the
faceplate and hardly see the glow of the bulb.
The tasks assigned to today's diver are becoming increasingly complex, and the costs associated
with getting a person to the underwater work site are steadily rising. From a cost perspective
alone, the job must be completed quickly, efficiently and safely.
Background:
The key to an efficient operation is being able to monitor the diver's work area. Real-time data
from a scanning sonar gives surface support personnel the perspective of what is happening on
bottom. The sonar can "see" beyond the eyes of the diver; it will monitor surrounding conditions.
The Kongsberg Mesotech MS 1000 scanning sonar is ideally suited to the following applications.
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search assignments
recovery/salvage operations
construction tasks
guiding a diver
monitoring the dive site
Solution:
Search Assignments:
The MS 1000 system is suited to monitor and guide diver search operations. For best results, the
diver should be tethered via an umbilical to the surface (for air/gas supply and hard-wire
KONGSBERG MESOTECH LTD. 1598 Kebet Way, Port Coquitlam B.C. Canada V3C 5M5
Tel: (604) 464 8144 Fax: (604) 941 5423 Email: [email protected]
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communications). The sonar head should be in a fixed position and mounted to allow maximum,
acoustic coverage of the search area. If the head is maintained in one location, an extremely
accurate, relative position search can be conducted without having to utilise an expensive
integrated positioning system.
It is important to maintain communication with the diver; the diver radio is best positioned next to
the MS 1000 processor. Diver’s bubbles and tanks make excellent acoustic targets. If, however,
the diver is lost amongst other bottom targets, instruct the diver to maintain position and exhaust
some air. The bubbles will be very visible on the sonar screen (the "unlimited" air from surface
supply is another advantage of using an umbilical).
With the sonar head in a fixed position, there is a simple method to determine that the area has
been totally searched. With the MS 1000 “track plotter” program the geographic position of the
diver can be updated and marked on the display. The grid search area can even be pre-plotted
When the screen is filled with diver position marks, the area has been covered.
The sonar can be used to direct the diver to a particular position. Instruct the diver to move in the
desired direction and use the reverse scan and cursor functions to continually update the diver's
position.
Recovery/Salvage Operations:
Diver involvement in recovery and salvage operations ranges in complexity from retrieving small
items by hand, to having to rig thousand kilogram loads. The scanning sonar can be utilised to
monitor the diver operation. In most situations the sonar can be deployed (on a tripod, or
weighted line) from the side of the support vessel, and positioned to scan the work area.
Because salvage and recovery often involves insurance companies, it is prudent to videotape
and/or hard copy the sonar information. Windows-based printers interface directly to an MS 1000;
the data can be stored to hard-drive or external recording device. BIT-map images of the sonar
screen may be stored directly to the computer. Annotation functions in the MS 1000 program
allow the operator to measure between targets, calculate the area, determine the height of objects
and label the data in real-time, or on the recorded data files.
Construction:
One of the best uses of the scanning sonar is in diver support for marine construction operations.
The MS 1000 can be used to monitor the work site, and check the underwater location of related
objects - before the diver descends. Additional monitors can be situated to allow equipment
operators to observe the underwater work area; the crane operator can now watch the position of
the underwater load.
Some additional construction applications for which the sonar can be used include:
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monitoring pipe lay operations
dredging and backfill operations
dock and pile undercutting/erosion studies
KONGSBERG MESOTECH LTD. 1598 Kebet Way, Port Coquitlam B.C. Canada V3C 5M5
Tel: (604) 464 8144 Fax: (604) 941 5423 Email: [email protected]
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Wet/Dry Diving Bell Deployment:
Installing the scanning sonar head on a wet or dry bell provides a stable reference platform to
acoustically monitor diving operations. The head is typically mounted in a protected location on
the exterior of the bell; the selected position should allow the widest angle of acoustic coverage.
Power to the head can either be from the surface, or it can be taken from the diving bell 24 vDc
supply (if applicable). A coax or twisted pair is used to transmit the sonar data to the surface when
power is bell-supplied. If power must be surface-supplied, a twisted pair and two power
conductors are required.
Many diving bell umbilicals are made with a coax to support underwater TV operations. If a spare
coax or twisted pair is not available, an option is to integrate a switching relay in the bell and utilise
the coax for either sonar or TV operations. This eliminates adding additional conductors to an
existing umbilical.
Mounting a sonar head on the bell allows surface personnel to monitor the dive site before the
divers lock out.
The use of scanning sonar will greatly assist many diver-related tasks. With this equipment,
information concerning the underwater work site can now be obtained before the dive is made.
Eliminating the uncertainty of where things are underwater will maximise diver efficiency, increase
safety, minimise costs, and lead to increased profits.
Diving safety is of paramount importance and Kongsberg Mesotech strongly advises that diving
operations be conducted in accordance to any and all Government/Industrial laws and/or
regulations.
For additional information or further support about this or any other acoustic application, contact
Kongsberg Mesotech Ltd.
Tel:
E-mail:
Web:
604 464-8144
[email protected]
www.kongsberg-mesotech.com
KONGSBERG MESOTECH LTD. 1598 Kebet Way, Port Coquitlam B.C. Canada V3C 5M5
Tel: (604) 464 8144 Fax: (604) 941 5423 Email: [email protected]
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KSML Scanning Sonar Tripod
Gimbaled Scanning Sonar Mount
KONGSBERG MESOTECH LTD. 1598 Kebet Way, Port Coquitlam B.C. Canada V3C 5M5
Tel: (604) 464 8144 Fax: (604) 941 5423 Email: [email protected]
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Current-Stabilized Deployment
Frame for 6K Sonar Head
simrad
Optional Kevlar Cable with
Kellums Grip to Deploy Sonar
Head
1/4" Wire Rope Cable
3/16" Aluminum Plate
Welded to Deployment
Frame
0 Degree Reference
Mark on 6K Sonar
Head
10-15 pound lead fishing
weight
KSML
KONGSBERG MESOTECH LTD. 1598 Kebet Way, Port Coquitlam B.C. Canada V3C 5M5
Tel: (604) 464 8144 Fax: (604) 941 5423 Email: [email protected]
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Image courtesy Fugro Chance, Lafayette, Louisiana
MS 1000 Sonar record of Diver walking a pipeline adjacent to an oil rig in the Gulf of Mexico
KONGSBERG MESOTECH LTD. 1598 Kebet Way, Port Coquitlam B.C. Canada V3C 5M5
Tel: (604) 464 8144 Fax: (604) 941 5423 Email: [email protected]
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Image courtesy LA County Sherriff’s Department
MS 1000 Scanning Sonar Record:Two divers swimming to a body in 80 metres water depth
KONGSBERG MESOTECH LTD. 1598 Kebet Way, Port Coquitlam B.C. Canada V3C 5M5
Tel: (604) 464 8144 Fax: (604) 941 5423 Email: [email protected]
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