Underwater diving is a widespread activity which is conducted for commercial and sporting reasons. Underwater diving can be a dangerous pastime for a diver is subjected to the elements such as underwater currents which may vary in strength and occurrence, the prevailing amount of light at the dive location, the visibility at the dive site, the water temperature, the pressure which is exerted by the water which is a function of the depth of the diving, and so on.

Dive sites are often a substantial distance from shore. Consequently conditions at the dive site may differ significantly from conditions at the shore. Moreover, at the dive site, the conditions at the water surface are not necessarily indicative of the conditions underwater. Diving may take place to a considerable depth, 50 metres or more, and the conditions under water, near surface, may differ materially from the conditions at the greater depths where the effects of current surges and other underwater activity are felt.

Apart from the danger to which a diver is exposed when underwater conditions are unsafe there is a substantial inconvenience factor when a dive party travels from an onshore location to a dive site, which may be many kilometres from the onshore location, only to find that conditions at the dive site mitigate against diving.

Apart from divers other people such as sailors, fishermen and surfers often require surface or underwater information about offshore locations which may be remote.

Information currently readily and regularly available is limited to that which relates to surface weather conditions and which is available from coastal weather stations.

SUMMARY OF THE INVENTION The invention provides, in the first instance, a method of monitoring conditions at an offshore location which includes the steps of: (a) anchoring a sensing apparatus at the location, and (b) transmitting information produced by the sensing apparatus to a receiver.

The sensing apparatus may be anchored at the location in any appropriate way and preferably is anchored by means of an anchor which extends to the seabed.

The sensing apparatus may be anchored at a predetermined depth from surface or at a predetermined distance from the seabed.

The receiver may be at the surface of the water or at a fixed location e. g. at shore.

Information produced by the sensing apparatus may be stored prior to being transmitted.

The transmission of information may take place continuously or at regular predetermined intervals or in response to an interrogating signal, according to requirement.

The sensing apparatus may be adapted to sense any appropriate or desired parameter or information pertaining to the location at which the apparatus is anchored.

The information which is produced by the sensing apparatus may, without being limiting, be selected from the following : the temperature of the water at the location ; the depth

of the sensing apparatus in the water; the strength of underwater currents at the location; the directions of underwater currents; the clarity of the water; the ambient light intensity; and underwater current surge activity.

The information which is produced by the sensing apparatus is not necessarily limited to underwater conditions for other conditions and phenomena, which can be monitored and reported on, relate to surface activities or events, some of which have underwater effects, for example: surface wind speed and direction; surface temperature; water content e. g. pH values, the existence of red tide and pollution levels ; cloud cover; the presence of bird and fish life; etc.

In one form of the invention the sensing apparatus includes a camera which produces video images of the water at the location.

The invention extends, in the second instance, to apparatus for monitoring conditions at an offshore location, the apparatus including sensing means, anchor means for anchoring the sensing means at the location, and a transmitter for transmitting information produced by the sensing means to a receiver.

The sensing means may include one or more sensors for sensing variations in, or for making absolute measurements of, one or more of at least the following : the temperature of the water at the location ; the depth of the sensing means in the water at the location; the strength of underwater currents at the location; the directions in which underwater currents flow ; the clarity of the water at the underwater location ; and the prevailing light intensity at the location.

Most of the aforegoing parameters would normally be measured underwater. However by using additional surface mounted sensors useful information can be readily generated relating to surface temperature; surface wind speed and direction; water content e. g. pH values, the existence of red tide and pollution levels ; cloud cover; the presence of bird, fish and other underwater marine life.

Marine or bird life may be detected using hydrophones, sonar devices, a video camera, or the like. The invention is not limited in this regard.

In one form of the invention the sensing means includes a camera for producing an image of the water at an underwater position at the offshore location.

The anchor means may be adapted to engage with the seabed at the location.

The sensing means may be positioned a predetermined distance above the anchor means so that the sensing means can be located at a predetermined depth below the surface of the water or, alternatively, at a predetermined distance above the seabed. As has been indicated though the apparatus may include a plurality of sensors which respectively detect different parameters or activities and some of the sensors may be located at the surface e. g. to measure wind speed and direction, cloud cover, surface temperature, and so on.

The sensing means may be connected to a buoy which floats on the surface.

The buoy may contain or be connected to a transmitter.

The apparatus may include a data logger or memory for storing information which is produced by the sensing means.

The information which is produced by the sensing means may be transmitted by the transmitter to the receiver on a continuous basis, at regular intervals, or in response to an interrogating signal.

In the last-mentioned case the apparatus may include a receiver which is responsive to an interrogating signal which thereupon transmits the information.

The interrogating signal may be encoded to ensure that the transmitter does not respond to unauthorised interrogating signals.

The transmitter may be a radio transmitter. Depending however on the position of the offshore location, the distance of the location from shore, and other physical factors, including natural geographic physical factors and manmade factors such as the existence of buildings and access roads etc, use may conveniently be made of a cellular network for transmitting the information.

A coastal cellular network is capable of allowing communication, between land and out to sea, over substantial distances, principally due to the relatively flat water surface and the lack of obstacles which would interfere with communication signals, particularly line of sight transmissions.

The use of cellular-based communication techniques can substantially lower installation and operating cost, and provides a facility whereby the available information can be conveniently accessed by large numbers of people, at low cost.

By levying a nominal charge on a cellular phone enquiry to a number from which the sensed information is made available sufficient revenue can be generated to cover, at least, operating costs of the system.

The sensing apparatus may be powered by means of a battery which may be replaceable or which may be recharged using any appropriate energy source, for example wave motion, wind energy or solar power.

The anchor means may be connected to the sensing means by means of a flexible cable or rope and the sensing means may be connected to the buoy by means of a flexible cable or rope. One or more conductors may extend between the sensing means and the buoy to enable information to be transmitted between these components and for power to be transmitted from the battery, when it is installed in the buoy, to the sensing means.

In a variation of the invention the buoy is used principally as a marker to indicate the position of the location and the sensing means includes a battery and a transmitter which is designed to work from an underwater location. This however is a less preferred form of the invention for there are technical problems to be overcome in effectively operating a transmitter at a below-surface position.

On the other hand if the buoy at surface is easily accessible and contains valuable electronic equipment it may become a theft target.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is further described by way of example with reference to the accompanying drawings in which: Figure 1 is a schematic representation of apparatus according to the invention used for monitoring conditions at an offshore location, and

Figure 2 illustrates in block diagram form electrical modules incorporated in the apparatus of the invention.

DESCRIPTION OF PREFERRED EMBODIMENT Figure 1 of the accompanying drawings illustrates apparatus 10 according to the invention which includes a buoy 12, a first sensing unit 14, an optional second sensing unit 15, and an anchor 16.

The buoy is connected to the first sensing unit 14 by means of a flexible cable 18 which incorporates electrical leads 20. The cable 18 and the electrical leads 20 are shown separate from one another in Figure 1 but this is merely for the purposes of identification. In practice the electrical leads may be incorporated in the cable or the two components may be connected to one another side by side. Generally the cable 18 will have substantially greater strength than the electrical leads 20 and the cable 18 therefore serves to connect the buoy physically to the first sensing unit while the leads 20 provide an electrical connection between the buoy and the sensing unit.

A second cable 22 extends from the sensing unit to the anchor 16. The anchor rests on the seabed 24.

The second sensing unit 15 is fixed to, or is incorporated in, the buoy 12. This unit is used primarily to detect surface conditions and thus may include substantially conventional sensors, which are not further described herein, to measure parameters such as wind speed, wind direction, surface temperature, light intensity, humidity, percentage cloud cover, and the like.

The apparatus 10 is prepared on land taking into account the conditions at which the apparatus is to be installed. Thus a decision is taken beforehand of the depth 26, below the surface of the water 28, at which it is desired to anchor the first sensing unit. This enables the length of the cable 18 to be calculated. From depth measurements previously taken at the location the distance 30 of the first sensing unit 14, above the seabed 24, is determined and this, in turn, sets the length of the cable 22.

The anchor 18 is any appropriate device which is able to withstand the forces which are exerted on the buoy and the first sensing unit by wind and currents, to ensure that the apparatus is kept firmly in position. In this respect use is made of technology which is known in the art.

The buoy floats on the water surface 28 and ensures that, within reason, the cables 18 and 22 are held taut. The first sensing unit 14 is therefore retained in position more or less at a fixed distance above the seabed and a fixed depth below the surface, while the second sensing unit 15 is kept at surface to enable its sensors to monitor the required surface conditions.

The buoy includes one or more buoyant members, not shown, which impart adequate buoyancy to the buoy. As is explained hereinafter the buoy 12 accommodates electrical equipment 40, shown in Figure 1, while the first sensing unit 14 accommodates electrical equipment 42 shown in Figure 2.

The water surface 28 can fluctuate considerably depending on wave action and the height of swells. To allow for this upwards and downwards movement the buoy could accommodate a cable control device 44 in which a length of the cable 18 is wound around a reel, not shown, which is acted on by a spring, not shown. As the buoy lifts,

with a rising swell, the increased upwards force on the buoy causes the cable reel to unwind while, when the buoy drops, in a valley between swell peaks, the cable is automatically rewound onto the reel, under the action of the spring. The movement of the cable reel could be monitored to obtain a measure of wave activity and swells at the installation position. It is not necessary, though, to use a device of the aforementioned type for, as an alternative, a small buoy 46 could be attached to the sensing device 14 to ensure that the sensing device is held at the predetermined distance 30 above the seabed. The length of the cable 18 from the sensing unit to the buoy is then made sufficiently long so that the buoy is able to float, within reason, in a manner which allows for water movement, as wave swells take place, without putting undue strain on the cable 18. The swell activity could, alternatively, be measured using a suitable pressure transducer.

The electrical equipment 40 includes, in this example, a receiver 48, a control unit 50 which may be microprocessor controlled, a transmitter 52, a data logger or memory 54, a battery 56, an optional solar panel 58, an antenna 60 which is connected to the receiver 48 and an antenna 62 which is connected to the transmitter 52. The antennae 60 and 62 are shown as separate devices but, in practice, a single antenna may be employed.

The electrical leads 20 extend from data logger to the electrical equipment 42 in the first sensing unit 14 and, as is indicated by a block 63, to the various sensors in the second sensing unit 15.

The equipment 42 includes a transmitter and multiplexer 64, and a plurality of sensors the nature and number of which depend on the parameters which prevail at the site and

which are to be monitored. In the illustrated example the sensors include a temperature sensor 66, a pressure monitor 68, a camera 70, a light meter 72, a current strength measuring device 74 and a current direction measuring device 76. The equipment 42 also includes a timer 78 and a memory 80.

The temperature sensor 66 may include any appropriate device which develops an electrical signal e. g. a resistor with a negative temperature coefficient. The pressure sensor 68 is preferably a load cell.

The camera 70 is a digital solid-state device of a type which is known in the art.

The light meter 72 comprises any appropriate component such as a light sensitive diode or a light dependent resistor. These devices have physical properties which are related to the amount of incident light to which the devices are exposed.

The device 74 for measuring the strength of a water current may be in the nature of a propeller which drives a small electrical generator. The propeller speed is directly related to the current strength and thus the electrical signal which is generated is an indicator of the current strength.

The device 76 for monitoring the direction of current flow may, in its simplest form, comprise a vane which is deflected to a position of least resistance by the current flow.

The vane is in turn connected to a compass and the needle of the compass is electrically monitored so that a signal which is indicative of its direction is obtained.

The sensors in the surface unit 15 are not described for, generally, they are of conventional construction and are designed and used to produce electrical output signals which are dependent on the parameter which is being monitored e. g. wind

speed, surface temperature, cloud cover, etc. These sensors are collectively designated by the reference numeral 82 in Figure 2.

The data produced by the array of surface and underwater sensors may be stored in the memory 80 at regular intervals. For example the timer 78 can, at intervals of say 15 minutes, initiate interrogation of each of the sensors 66 to 76 and the surface sensors.

Upon interrogation each sensor outputs a signal, in digital form, which is indicative of the strength of the parameter monitored by the sensor. The data is assembled in the memory 88 and is then multiplexed, if necessary, or otherwise is placed in different pre- assigned fields in a data word whereafter the data word is transmitted by the transmitter 64 to the data logger 54.

The temperature and pressure readings will normally not vary rapidly and intermittent measurements of these parameters will generally be adequate. The camera 70 may be used to produce underwater images at regular intervals. The amount of data needed to transmit an image may be substantial and various techniques may be resorted to in order to reduce the amount of transmitting capacity which is required. For example an image could be taken by the camera every 15 minutes and data relating to differences in successive images can be transmitted instead of transmitting all the data pertaining to each image.

Normally the light intensity at a location will vary gradually. Thus it is possible to make surface and underwater light intensity measurements at regular intervals. On the other hand the light intensity may vary abruptly particularly due to strong underwater current flows which may occur at irregular intervals. It is highly beneficial to have prior knowledge of this type of situation and, accordingly, the light meter and the device 74 for

measuring the strength of an underwater current can function substantially continuously.

Each device can still transmit a signal to the memory 80 at a regular interval but, in addition, can run continuously and sense any abrupt change, say in excess of a predetermined level, which occurs. This feature enables gusts or intermittent irregular changes in light and current strength to be detected.

Similarly the device 76 which monitors the direction of currents underwater should function continuously. It is important to know whether an underwater current is flowing in one direction or in variable directions. Abrupt unexpected changes in current strengths and flow directions can give rise to dangerous underwater conditions.

The electrical equipment 42 is housed in the sensing unit 14 in a waterproof manner.

The camera and light meter are directly exposed to the water through appropriate lenses and it will be necessary at regular intervals to clean these lenses. This can be done however when diving takes place at the particular site.

The transmitter 64, under the control of the timer 78, transmits data at regular intervals to the data logger 54. The transmission takes place along the electrical leads 20. The data logger 54 stores the received information in sequential form, as it is received.

Information which is indicative of abrupt and irregular changes in underwater conditions, for example changes in light intensity, current strength and current direction, may be stored separately with the times at which the changes take place also being logged.

These aspects may be determined according to requirement taking into account the most effective way of presenting the information which is generated by the sensing unit 14.

The information which is contained in the data logger 54 may be transmitted, again at regular intervals, by the transmitter 52 to a location, on shore, at which the information is analysed and displayed. Alternatively, or additionally, the onshore location contains a transmitter which can be operated, according to requirement, and which sends an interrogating signal to the buoy 12 which is received by the receiver 48. When the interrogating signal is received the data logger 54 is prompted to download its information to the transmitter 52 which then transmits an appropriate signal, containing the stored information, to the onshore location. The interrogating signal is preferably encoded to ensure that the data logger 54 can only be interrogated by authorised personnel.

Depending on circumstances and conditions the transfer of information can take place at radio frequencies.

If however an existing cellular telephone network is available which provides communication coverage of the installation site then data transfer can effectively be achieved using cellular techniques using principles which are known in the art and which are therefore not further described herein.

The control unit 50 houses a timer, not shown, and a microprocessor which monitors and controls the operation of the remaining components in the equipment 40 and the equipment 42. The various components are powered by the battery 56. For example the control unit 50 monitors the status of the battery and the functionality of the different sensors in the equipment 42 and the surface unit 15, and if a malfunction occurs, or if the battery needs to be replaced or recharged, causes an appropriate warning signal to be transmitted to the control site onshore.

As an option the buoy 12 includes a solar panel 58 fixed to it at a position at which the panel is exposed to sunlight. The panel 58 produces an electrical signal which is used to recharge the battery 56. The panel can also be used, simultaneously, to provide a measure of surface light intensity or of the degree of cloud cover out at sea.

The apparatus of the invention makes it possible to monitor conditions which prevail at surface and underwater at an offshore site. The conditions which are monitored are not limited but are chosen according to requirement. The conditions may however be indicative of the safety or acceptability of the site, as a dive site, according to predetermined criteria. The information is available onshore at regular intervals or upon demand, particularly if cellular communication techniques are used. By using the information judiciously it is possible to make a decision, while on land, on the suitability of the site for diving, or any other activity. In particular this holds distinct advantages for dive operators who are then able to offer greater safety and certainty when making a decision about a dive site.