GB2391312A

GB2391312A - Underwater detection of a decomposing life form

Info

Publication number: GB2391312A
Application number: GB0217515A
Authority: GB
Inventors: John Patrick Chilton; Christopher Teal
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-07-30
Filing date: 2002-07-30
Publication date: 2004-02-04
Also published as: GB0217515D0

Abstract

A decomposing life form , typically a carcass, located underwater is detected using an underwater vehicle unit with a sensor(s)/detector(s) mounted thereon for sensing chemical compounds e.g. CH4 or H2S discharged by the carcass. Output from the sensor(s)/detector(s) is transferred via an information link to a control unit located on the vehicle or remotely. The sensor(s)/detector(s) may be on a manned submersible or a remotely operated vehicle. Utility may be in underwater searches for a body.

Description

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METHOD AND APPARATUS FOR UNDERWATER DETECTION

This invention relates to underwater detection. It is particularly concerned with the detection of decomposing life forms Present methods used for the location of carcasses underwater are hampered by a variety of factors including one or more of the following: poor underwater visibility; depths beyond diving range; the operational cost and availability of submarine, or remotely operated vehicle search procedures; tidal streams and ocean currents; fast flowing rivers; inaccessible search locations.

A soft carcass presents a poor sonar target and will not always be detected by these instruments. In addition operators of sonar systems cannot always differentiate between carcasses and other underwater features such as mud mounds, depth contours, rocks or debris. As a result, each probable target has to be identified, which results in a protracted searches at a time when a quick result is vitally important.

Particularly when forensic issues arise in some underwater environments body decomposition rates and mechanical degeneration obliges searches for a body and its recovery to be completed swiftly before the evidence disappears.

According to a first aspect of the present invention there is provided a method of underwater detection comprising the steps of: locating on a vehicle unit for underwater operation a detector for a chemical compound typically discharged by a carcass during decomposition or a plurality of such detectors each being for a different such compound;

l connecting the or each sensor by an information link to a control unit whether located on the vehicle unit or on a remote surface or other vehicle or to both the vehicle unit and a remote vehicle; undertaking a detection search by causing the vehicle unit to follow a predetermined search path at a selected depth; operating the, or each, sensor and establishing whether the sensor, or any of them, detect the presence of a chemical compound and providing as output from the, or each, sensor information as to the presence or absence of the or any chemical compound as aforesaid to the control unit by the information link; using the information received at the control unit to establish the presence or absence of a significant quantity of a given chemical compound as aforesaid.

According to a second aspect of the present invention there is provided apparatus for underwater detection comprising: a vehicle unit for underwater operation; at least one detector for a chemical compound typically discharged by a carcass during decomposition or a plurality of such detectors each being for a different such compound; the or each detector being mounted on the vehicle unit: an information link whereby output from the or each detector on the vehicle unit can be transferred to a control unit either located locally on the vehicle unit or located remotely from the vehicle unit or to both for interpretation.

This application proposes that a range of specifically calibrated sensors can detect various chemical compounds discharged by carcasses during decomposition.

SENSOR SELECTTON AND CONFIGURATION

Several categories of chemical compound detectors are in use underwater, their uses include: environmental monitoring of water quality and pollution; detection of hydrocarbon emissions from either natural sources or oil industry related activities; oceanographic research.

l l It is proposed that a range of different suitable sensors are combined within a single underwater housing, and that the data output from each sensor is presented as visual and/or aural information to the surface operator or diver.

The sensors are selected and calibrated so that the combined system detects the range of chemical compounds or other detectable emissions that are discharged at various stages of carcass decomposition.

SENSOR UTILISATION

In order for the proposed detection method to be used in all underwater situations, differing configurations of instruments will require to be designed: 1 Hand Held, Self-contained System This is intended for deployment over the side of a small vessel, to be carried by a wading operator in shallow water, or, to be carried by a diver. This unit is a battery-

powered instrument, similar in size to that of a portable metal detector. The sensor information is presented to the operator in the form of simple LED or Liquid Crystal Display formats. Each type of sensor supported by the system has a separate display.

The operator is provided with aural information, with differing tones being allocated to each type of sensor. Adjustable Gain Control and Alarm Levels are available for each sensor. The system is equipped with a microprocessor for recording data for later analysis.

2 Sensor Assembly and Separate Control Station This is intended for remote operations to be conducted outwith the reach of the sensor operator. The components of this station consist of the sensor assembly and transmitter, an umbilical cable and a remote display and control station.

The sensor assembly can be deployed by an umbilical into deep water or other hazardous location. The data from each sensor is transmitted along the umbilical to the remote control station where the operator can monitor the output from each sensor. As

'd' ':e ' (. tes:' in a hand held system, alarms and gain levels are adjustable, and data can be recorded from the remote station. Power for the sensor array is distributed either from the control station, or, from a remote operating vehicle or a towed device that is carrying the sensor.

SEARCH PROCEDURES USINC THE SENSOR ARRAY.

While it is not intended to identify all scenarios where the sensor will be deployed various activities will have to be conducted in order for an operator to establish system functionality and sensitivity.

PREPARATION FOR SEARCH USING THE SENSOR SYSTEM

An initial requirement will be to identify any water flow patterns within the area to be searched. Chemical compounds emitted by a carcass will be carried by river, tidal or current flow paths and so the sensor will not detect emissions from a carcass up-

stream, up-tide or up-current of the carcass.

Having established the direction of search methodology, the operator will then have to record the background readings detected by each type of sensor within the instrument.

This background level test is required, as any biomass carried by the water will be

detected by some of the sensors within the array. The sensor will be taken to various locations around the search area, and backgrounds levels will be recorded at each

location. If the depth of water varies within the search pattern, a procedure will be developed to ensure that the sensor is deployed and monitored at selected depth ranges.

SEARCHING WITH THE SENSOR SYSTEM

The system is used to identify zones within a search pattern that are indicating a high level of the selected emissions, which may, or may not be, from a carcass.

When deployed in a flowing river, or water transportation system, the sensor will simply be transported upstream. As the source of emissions is approached the signal strength will increase, and the operator will visually observe the exact location where the signal strength has decreased. This would provide a fix on a possible location of a carcass. Either wading searchers or divers would then physically search the designated area. When deployed in coastal or estuarine conditions the search pattern will be dictated by a variety of factors. The system operator will have to determine the optimum tidal conditions including water flow direction and speed, and background readings that

will enable a reasonable search to be conducted.

In still water conditions the chemical compounds will radiate in all directions and the search pattern will be that of a grid layout. The sensor will be transported around the grid and signal strengths plotted electronically or manually onto a chart. The data will then be analysed to determine areas of high sensor response.

When high levels of sensor activity are recorded, the location will be marked and a search may be instigated utilising divers or remote systems.

The remote sensor will be small enough to enable it to be installed on ROVs, manned submersibles or towed sonar devices. The advantage of installing the unit on a free-

swimming ROV is that cameras and sonar can immediately be directed at any areas of high sensor activity.

if the sensor is simply deployed over the side of a vessel working in an area of reasonable water visibility, a downwards-looking camera could also be attached to the same umbilical. This allows the operator to conduct a simple visual search in areas of high sensor readings.

l (: t l l l An exemplary embodiment of the invention will now be described with reference to the accompanying drawing of which the sole figure is a perspective view of an underwater location.

The drawing shows a shallow seawater environment 1 I with a sea bed 12 and a sea surface 13 on which a craft 14 is in attendance.

A body 15 of a dead person has been submerged for several days. Natural degeneration has resulted in the emission of bubbles 16 of methane gas. While the amount of methane will progressively decrease it is understood that other gases will be emitted as time passes including hydrogen sulphide.

A shallow water diver 18 is equipped with a lightweight underwater zero gravity vehicle 19 equipped according to the present invention. The vehicle 19 includes an openwork housing 20 for chemical compound detectors D1 to D4 including individual detectors for methane and hydrogen sulphide. The housing 20 includes a control panel 21 on which is mounted controls 22 and a video display unit 23 whereby information provided by the detectors D1 to D4 is displayed in a readily assimilated manner. The housing also contains a battery system for powering the systems on the vehicle 19.

The vehicle 19 is attached by an umbilical 25 to the craft 14 so that information from the detectors D1 to D4 are available simultaneously to the diver 18 and to observers on the craft 14. A phone link between craft 14 and the diver 18 is also provided by way of the umbilical 25.

The vehicle 19 includes means for identifying the position of the vehicle 19 at any point and can also include a camera to enable surface users of the equipment to see, to some extent, the region in front of the vehicle 19.

The development of the proposed system will enable underwater searches for decomposing bodies to be carried out by more efficient means than are presently

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l l l l available. By careful selection and calibration of the sensors utilised, operators will be able to deal with search areas which are large in size, otherwise inaccessible or potentially or actually dangerous systematically and efficiently.

The method and apparatus are applicable to any sort of water environment whether involving fresh or salt water. Versions of the invention can be used for searching in any water involving environment including rivers, lakes, estuaries, canals, man made water courses or reservoirs; coastal and sea. The apparatus of the invention can be in the form of readily portable independent units or involve the provision of arrays of detectors on a submersible vehicle such as an ROV or a manned submersible.

Claims

( CLAIMS

1 A method of underwater detection comprising the steps of: locating on a vehicle unit for underwater operation a detector for a chemical compound typically discharged by a carcass during decomposition or a plurality of such detectors each being for a different such compound; connecting the or each sensor by an information link to a control unit whether located on the vehicle unit or on a remote surface or other vehicle or to both the vehicle unit and a remote vehicle; undertaking a detection search by causing the vehicle unit to follow a predetermined search path at a selected depth; operating the, or each, sensor and establishing whether the sensor, or any of them, detect the presence of a chemical compound and providing as output from the, or each, sensor information as to the presence or absence of the or any chemical compound as aforesaid to the control unit by the information link; using the information received at the control unit to establish the presence or absence of a significant quantity of a given chemical compound as aforesaid..

2 Apparatus for underwater detection comprising: a vehicle unit for underwater operation; ' at least one detector for a chemical compound typically discharged by a carcass during decomposition or a plurality of such detectors each being for a different such compound; the or each detector being mounted on the vehicle unit: an information link whereby output from the or each detector on the vehicle unit can be transferred to a control unit either located locally on the vehicle unit or located remotely from the vehicle unit or to both for interpretation.

3 A method of underwater detection as hereinbefore described with reference to the accompanying drawing.

4 Apparatus for as hereinbefore described with underwater detection as hereinbefore described with reference to the accompanying drawing.