GB2550980A

GB2550980A - Improvements in or relating to buoys and/or SARTs

Info

Publication number: GB2550980A
Application number: GB1612563.5A
Authority: GB
Inventors: Yuan Haifeng
Original assignee: Quick-Teck Electronics Ltd
Current assignee: Quick-Teck Electronics Ltd
Priority date: 2016-07-20
Filing date: 2016-07-20
Publication date: 2017-12-06
Anticipated expiration: 2036-07-20
Also published as: GB201612563D0; GB2550980B

Abstract

An AIS marine buoy or Search and Rescue Transmitter (AIS-SART) 10 reacts to receipt 5,6 of an Automatic Identification Signal (AIS) from another AIS source by transmitting 7 an AIS signal comprising its location. The buoy or SART may receive and validate IMO or MMSI numbers from the source and may then alter a time interval between transmissions e.g. depending on the quantity of IMO or MMSI numbers received; its own speed; the speed of the source; or their relative speeds. The interval may be shortened if they are moving quickly or approaching one another; or lengthened if they are moving slowly or diverging. Alternatively the buoy or SART may not use AIS and/or may place power-saving limitations 8 on transmitter 4 or GPS receiver 1 whist an internal battery level is low and no signal is received. Alternatively or additionally the transmitted AIS signal may comprise an identification of the buoy or SART.

Description

Improvements in or Relating to Buoys and/or SARTs

The present invention relates to a marine buoy or SART (Search and Rescue Transmitter), in particular, a passive AIS buoy or AIS-SART. The invention also relates to a method for operating a passive AIS buoy or AIS-SART, and methods for conserving power in a buoy or SART.

Automatic Identification System (AIS) is a maritime communications system designed for short range ship-to-ship and ship-to-shore communications. Depending upon the VHF frequency band used, the radio range of AIS from ship-to-ship is approximately 40 to 60 km, which corresponds to little more than normal visibility on the high seas. Coastal stations are able to cover a greater radius of up to 100 km as a result of their relatively high positions.

The AIS system supports a number of different types of signals. The principal AIS signal sent by an AIS unit is a position report that provides information pertaining to a ship's identification, location, course, speed and other details. Some AIS units also have receivers, which enables a ship to receive AIS signals emitted by other nearby ships.

The use of AIS is now mandatory as an aid to navigation, safety and collision avoidance on all ships over 300 tons that are engaged on international voyages. Recently, more and more small vessels, such as small boats and yachts, have AIS units fitted on board to reduce the risk of collision and, thereby, enhance safety at sea. With the hardware cost of AIS units continually dropping, many other applications have arisen, such as marine rescue, traffic management, coast guard work, sea surface current monitoring, and marine animal tracking. In addition, AIS buoys, i.e. a buoy which includes AIS receivers / transmitters, are now used in a range of applications, such as fishing net tracking, and ice-flow and lighthouse monitoring, and marine animal tracking. To enable tracking, the buoy is, for example, provided with a GPS receiver and a transmitter for transmitting its position and identity to a neighbouring party, whether a vessel or the like. The receiving party, typically, has a navigation system that is adapted to receive signals according to the AIS standard and can, therefore, track the buoy by receiving the AIS signals. AIS buoys are generally powered by rechargeable batteries that must be recharged regularly. Some other newer AIS buoys have hybrid power sources, whereby solar energy or wind is used as an additional power source. However, these additional power sources are only supplementary power sources, as the power drain of a standard AIS buoy is too great for such additional power sources alone.

As such, despite the additional power sources, AIS buoys still need to be retrieved and placed in a charging dock for recharging. Reaching some AIS buoy’s location can be costly and time-consuming, since a ship or helicopter must be manoeuvred into place. Sometimes this operation may be dangerous.

Further, a standard AIS buoy may transmit every 3 to 5 minutes if slow moving or relatively stationary, or every six seconds if on a moving ship. Consequently, the practical life of the battery of the buoy before recharging is required is, typically, 7 to 18 days. In many applications, the AIS buoys do not move as quickly as a vessel and, so, it is not necessary for the buoy to send out an AIS message every few minutes, as would be the case with a standard AIS buoy.

Consequently, there is a need for an improved AIS buoy.

An AIS-SART (AIS Search and Rescue Transmitter) is very similar technology-wise, if not identical, to an AIS buoy but is used to locate a distressed craft or vessel - as such, they are often located in a lifeboat. The AIS-SART is activated in an emergency situation and emits an AIS signal which is detected by surrounding ships, etc. as a way of locating the AIS-SART and the lifeboat. AIS-SARTs typically have a limited battery life, as they are a self-contained unit, and, therefore, so as to keep the AIS-SART activating for longer, there is a need for an improved AIS-SART.

Accordingly, in a first aspect the present invention provides a passive AIS buoy or AIS-SART comprising: means for determining a location of the buoy or SART; means for receiving an AIS signal from another AIS source; means for transmitting an AIS signal; and means for reacting to receipt of said AIS signal from another AIS source; wherein, the passive AIS buoy or AIS-SART is capable of receiving the AIS signal from said another AIS source and reacting to that by transmitting an AIS signal comprising the location of the buoy or SART.

Preferably, comprising solar and/or wind power generation, such that the buoy or SART is capable of working indefinitely without external recharging.

Preferably, the passive AIS buoy or AIS-SART is capable of transmitting an AIS signal comprising the location and identification of the buoy or SART.

Preferably, comprising means for receiving an IMO or MMSI number from said another AIS source. Most preferably, comprising means for validating an IMO or MMSI number from said another AIS source before reacting thereto.

Preferably, the means for determining a location of the buoy or SART is GPS, GLONASS, Galileo, and/or BeiDou satellite navigation systems.

Preferably, comprising means for altering a transmit interval time, T, between respective transmissions following receipt of said AIS signal from said another AIS source.

Preferably, comprising: means for altering a/the transmit interval time, T, between respective transmissions depending upon a speed of movement of the AIS buoy or AIS-SART itself and/or a speed of movement of said another AIS source; or means for altering a/the transmit interval time, T, between respective transmissions depending upon the amount of IMO and/or MMSI numbers received.

Most preferably, comprising means for altering a/the transmit interval time, T, between respective transmissions depending upon a relative closing speed of the AIS buoy or AIS-SART and said another AIS source, or their relative diverging speed.

Preferably, shortening the transmit interval time, T, if the AIS buoy or AIS-SART and/or said another AIS source is/are moving quickly, or the AIS buoy or AIS-SART and said another AIS source are moving closer together.

Preferably, lengthening or maintaining the transmit interval time, T, if the AIS buoy or AIS-SART and/or said another AIS source is/are moving slowly, or the AIS buoy or AIS-SART and said another AIS source are moving further apart.

Most preferably, the buoy or SART comprises: a GPS receiver; two AIS receivers, one for each AIS channel; and an AIS transmitter.

Alternatively to the GPS receiver mentioned above, the buoy or SART may comprise a GPS, GLONASS, Galileo and/or BeiDou satellite navigation receiver.

Further preferably, additionally comprising a baseband processor component, and/or a power supply and management component.

According to a second aspect of the invention, there is provided a method for operating a passive AIS buoy or AIS-SART, the method comprising: determining a location of the buoy or SART and receiving an AIS signal from another AIS source; or receiving an AIS signal from another AIS source and determining a location of the buoy or SART; and reacting to receipt of the AIS signal from said another AIS source by transmitting an AIS signal comprising the location of the buoy or SART. Preferably comprising transmitting an AIS signal comprising the location and identification of the buoy or SART. Further preferably, wherein the identification of the buoy or SART is its IMO and/or its MMSI number.

Preferably, the method comprising receiving an IMO or MMSI number from said another AIS source. Most preferably, comprising validating the IMO or MMSI number from said another AIS source before transmitting.

Preferably, altering a transmit interval time, T, between respective transmissions following receipt of the AIS signal from said another AIS source.

Preferably, altering a/the transmit interval time, T, between respective transmissions depending upon the amount of IMO and/or MMSI numbers received Preferably, altering a/the transmit interval time, T, between respective transmissions depending upon a speed of movement of the AIS buoy or AIS-SART itself and/or a speed of movement of said another AIS source.

Most preferably, altering a/the transmit interval time, T, between respective transmissions depending upon a/the relative closing speed of the AIS buoy or AIS-SART and said another AIS source, or their relative diverging speed.

Preferably, shortening and/or maintaining the transmit interval time, T, if the AIS buoy or AIS-SART and/or said another AIS source is/are moving quickly, or the AIS buoy or AIS-SART and said another AIS source are moving closer together.

Preferably, lengthening and/or maintaining the transmit interval time, T, if the AIS buoy or AIS-SART and/or said another AIS source is/are moving slowly, or the AIS buoy or AIS-SART and said another AIS source are moving further apart.

Preferably, recharging an internal battery solely through means of solar and/or wind power generation conducted on the buoy or SART.

Preferably, the buoy or SART comprises one or more features according to the first aspect.

According to a third aspect, there is provided a method for conserving power in a buoy or SART, the method comprising: checking an internal battery level of the buoy or SART; if the battery level is below a threshold, and no signal has been received from another signal source, placing a means for transmitting and/or a means for determining a location of the buoy or SART in standby; remaining in standby until either: upon subsequently checking the battery level, the level is above the threshold; or a signal is received from said another signal source; and transmitting a signal comprising the location of the buoy or SART.

Preferably, if the battery level is above the threshold, transmitting a signal comprising the location of the buoy or SART every transmit interval time, Ti.

Preferably, if the battery level is below the threshold, independently of any transmitting following receipt of an/said signal from said another signal source, transmitting a signal comprising the location of the buoy or SART every transmit interval time, T2, where T2 > T1.

Preferably comprising transmitting a signal comprising the location and identification of the buoy or SART. Further preferably, wherein the identification of the buoy or SART is its IMO and/or its MMSI number.

Preferably, the method is a method for conserving power in an AIS buoy or AIS-SART, and the buoy or SART is capable of receiving and/or transmitting AIS signals.

According to a fourth aspect, the present invention provides a method for conserving power in a buoy or SART, the method comprising: checking an internal battery level of the buoy or SART and setting a transmit interval time, Ti, at which transmit interval time the buoy or SART will transmit a location of the buoy or SART; if the battery level is below a threshold, and no signal has been received from another signal source, setting a transmit interval time, T2, in which T2 > T1; if a signal is received from said another signal source, independently of either transmit interval time, T1 orT2, transmitting a signal comprising the location of the buoy or SART.

Preferably, the methods of the third and/or fourth aspect comprise one or more of the following.

Preferably, receiving an IMO or MMSI number from said another signal source. Most preferably, validating the IMO or MMSI number from said another signal source before transmitting.

Preferably, altering the transmit interval time, T, between respective transmissions following receipt of the AIS signal from said another AIS source.

Preferably, altering a/the transmit interval time, T, between respective transmissions depending upon a speed of movement of the AIS buoy or AIS-SART itself and/or a speed of movement of said another AIS source.

Preferably, altering a/the transmit interval time, T, between respective transmissions depending upon the amount of IMO and/or MMSI numbers received.

Preferably, altering a/the transmit interval time, T, between respective transmissions depending upon a/the relative closing speed of the AIS buoy or AIS-SART and said another AIS source, or their relative diverging speed.

According to a further aspect, the present invention provides a data carrier, disk, chip, computer, tablet or the like programmed to implement the method of any one of the second, third or fourth aspect or their consistory clauses, or a piece of software stored on any such device coded to implement the method of any one of the second, third or fourth embodiment or their consistory clauses.

The present invention also relates to a passive AIS buoy or AIS-SART comprising: means for receiving an AIS signal from another AIS source; means for transmitting an AIS signal; and means for reacting to receipt of said AIS signal from another AIS source; wherein, the passive AIS buoy or AIS-SART is capable of receiving an AIS signal from said another AIS source and reacting to that by transmitting an AIS signal comprising an identification of the buoy or SART.

The present invention also relates to a passive buoy or SART comprising: means for determining a location of the buoy or SART; means for receiving a signal from another signal source; means for transmitting a signal; and means for reacting to receipt of said signal from another signal source; wherein, the passive buoy or SART is capable of receiving the signal from said another signal source and reacting to that by transmitting a signal comprising the location of the buoy or SART.

The present invention also relates to a method for operating a passive buoy or SART, the method comprising: determining a location of the buoy or SART and receiving a signal from another signal source; or receiving a signal from another signal source and determining a location of the buoy or SART; and reacting to receipt of the signal from said another signal source by transmitting a signal comprising the location of the buoy or SART.

Those skilled in the art will understand that all AIS signals received will need to be decoded (for example through demodulation in an AIS receiver module) before valid information (such as the IMO, MMSI, ship type, its position, etc.) are obtained.

Advantageously, the present invention provides an energy efficient, low-power consumption AIS buoy or AIS-SART that is activated and transmits an AIS message after it has been triggered by a remote AIS transponder. The buoy or SART is passive, as it has the capability of going into a form of standby mode, and can then be activated by receipt of an AIS signal from another signal source. Transmitting uses more power than receiving and, so, by putting the transmitter and/or the GPS receiver in standby and/or by increasing the transmit interval time, power consumption is kept to a minimum. Additionally, by generating power on board the buoy or SART, either through solar panel(s) or wind power generator(s) alone, or through a combination of both, the buoy or SART can operate indefinitely without requiring external recharging. Advantageously, operators of the proposed buoys can save time and engineering costs, which would be otherwise associated with reaching a standard buoy and recharging its batteries. Further, as the buoy can work indefinitely, the AIS buoys of the present invention may be used in more rugged areas, since operators do not need to reach them regularly.

The invention will now be disclosed, by way of example only, with reference to the following drawings, in which:

Figure 1 is a schematic drawing of components of a passive AIS buoy;

Figure 2 is a schematic drawing of location determining components of the passive AIS buoy of Figure 1;

Figure 3 is a schematic drawing of receiver and transmitter components of the passive AIS buoy of Figure 1;

Figure 4 is a schematic flowchart of a method for conserving power in an AIS buoy.

Figure 1 shows components of a passive AIS buoy, identified generally by reference 10, which includes a GPS front end component 1, a GPS receiver component 2, an AIS front end component 4, two AIS receiver components 5; 6, respectively, an AIS transmitter component 7, a baseband processor component 3, and power supply and management component 8.

As shown in detail in Figure 2, the GPS front end component 1 includes a low noise amplifier (LNA) 1.1 and a band pass filter 1.2. The LNA 1.1 is connected to an external GPS antenna 1.3 and receives and amplifies the incoming RF (radio frequency) signals. The amplified RF signal is then routed through the band pass filter 1.2 so that any out of band RF signals will be rejected, before sending the signals to the GPS receiver component 2. The GPS receiver component 2, which receives the RF signals from the GPS front end component 1, includes a down converter 2.1, an Intermediate Frequency (IF) amplifier 2.2 and an analogue-to-digital converter (ADC) 2.3. Using mixers, the down converter 2.1 converts the signal from the GPS front end component 1 to an IF frequency by mixing the input RF signal with a Local Oscillator (LO) signal. The resulting analogue IF signal is then amplified by the IF amplifier 2.2 and converted to a digital IF signal by the ADC 2.3.

As shown in detail in Figure 3, the AIS front end component 4 includes a low pass filter 4.1, a Transmit/Receive (T/R) switch 4.2, an LNA 4.3 and a splitter 4.4.

The low pass filter 4.1 is connected with an external AIS antenna 4.5 and is used to reject undesired high frequency noise received by the antenna 4.5. The T/R switch 4.2 is connected to the low pass filter 4.1 and allows transmit and receive operation with a single antenna. The switch 4.2 toggles the antenna 4.5 back and forth between the receiver(s) 5; 6 and transmitter 7, a switching time interval being under the control of the baseband processor component 3. During the receiver time interval, the received RF signals are sent to the LNA 4.3 for amplification and then on to the splitter 4.4, to split them evenly into two AIS channels. During the transmitter time interval, RF signals from the AIS transmitter component 7 are sent to the low pass filter 4.1, through the switch 4.2, and then transmitted by the antenna 4.5. AIS receiver components 5; 6 provide two independent receiver modules that simultaneously receive two RF signals on two AIS frequency channels. Each receiver component 5; 6 respectively includes a Surface Acoustic Wave filter (SAW) 5.1; 6.1, a down converter 5.2; 6.2, an IF amplifier 5.3; 6.3 and an ADC 5.4; 6.4. Taking channel 1 (RX1) as an example, the RF signals received from the AIS front end component 4 are sent to the SAW1 filter 5.1 from the splitter 4.4. The SAW1 filter 5.1 eliminates non-AIS frequencies from the signals and then they are mixed with a low frequency signal from a Local Oscillator in down converterl 5.2. In this way, the down converterl 5.2 shifts the RF signal down to IF, which then routes it to the IF ampliflierl 5.3. The IF ampliflierl 5.3 enhances the down converted IF signals and then sends them to ADC1 5.4, which digitises the signals. The digital signal is then sent to the baseband processor component 3.

The AIS transmitter component 7 includes a Digital-to-Analogue converter (DAC) 5.2 and a power amplifier (PA) 5.1. During the transmission time interval, an output AIS message generated from the baseband processor component 3 is fed to the DAC 5.2, which converts this digital data into analogue signals. The analogue signal from the DAC 5.2 is then filtered by a band pass filter (BPF) to select the AIS frequency, and then fed to the power amplifier (PA) 5.1. The amplified signal is then sent to the low pass filter 4.1 before being transmitted by the AIS antenna 4.5.

The baseband processor component 3 is connected to the GPS receiver component 2, the AIS receiver components 5; 6, the AIS transmitter component 7, and the power supply and management component 8. It is responsible for receiving the digital signal from the GPS receiver component 2, receiving the digital signals from the AIS receiver components 5; 6, and transmitting the digital signal to the AIS transmitter component 7.

As shown in Figure 1 in more detail, the power supply and management component 8 includes a solar panel 8.1, a rechargeable battery 8.2, and a power management and monitoring unit 8.3. The solar panel 8.1 uses light energy from the sun to generate electricity through the photovoltaic effect. The rechargeable battery 8.2 is connected to the solar panel 8.1 to save electricity/power and provide additional power to the buoy 10. The power management and monitoring unit 8.3 is connected to the rechargeable battery 8.2 and, under control of the baseband processor component 3, checks the battery level regularly. It also protects the battery and ensures that it is working in a safe condition by monitoring the voltage, current and temperature. By way of an alternative, the power supply and management component 8 may include a wind power generator (not shown), either in addition to the solar panel 8.1 or instead thereof, together with the rechargeable battery 8.2, and power management and monitoring unit 8.3. A method of use of the buoy 10 will now be described, with reference to Figure 4, in which a transmit interval time, T2, is greater than a transmit interval time,T1. The method includes nine main steps, referenced in Figure 4 as 101 to 109, respectively.

Step 1 (ref. 101)- Power up the AIS buoy 10. A transmit interval time, T, of the AIS transmitter is set as T1. A battery level checking interval time, P, is set as P1. Go to Step 2.

Step 2 (ref. 102) - The GPS receiver component 2 receives the satellite signals and sends the location data to the baseband processor component 3. Go to Step 3.

Step 3 (ref. 103) - The baseband processor component 3 checks the battery level. If the remaining level of the battery is higher than a pre-defined percentage (a%) - ‘Yes’ go to Step 4. Otherwise, ‘No’ go to Step 5.

Step 4 (ref. 104) - Set the transmit interval time, T, as T1, then go to Step 8. Step 5 (ref. 105) - The baseband processor component 3 checks the information received from the AIS receiver components 5; 6 and checks if any AIS signal has been received, in particular if any valid International Marine Organisation (IMO) or Maritime Mobile Service Identity (MMSI) number has been received. If ‘Yes’, go to Step 6 as this indicates that there are AIS sources nearby. Otherwise, ‘No’ go to Step 7 to save battery energy.

Step 6 (ref. 106) - Set the AIS transmit interval time, T, as T2 (less frequent transmission) then go to Step 8.

Step 7 (ref. 107) - Configure the AIS transmitter component 7 and the GPS receiver component 2 for standby mode then go to Step 9. During standby mode, the AIS transmitter and GPS receiver will not operate.

Step 8 (ref. 108) - The AIS transmitter component 7 sends rescue and/or location message(s) at the configured transmit interval times (T1 or T2).

Step 9 (ref. 109) - The baseband processor component 3 checks the battery level every time, P1 - go to Step 2.

The method then cycles through steps 2 to 9 (refs. 102 to 109) in normal operation, as per the dependencies identified above.

Although the present invention has been exemplified with reference to an AIS buoy, the invention also extends to an AIS-SART, and methods relating to an AIS-SART. As the technology behind the proposed AIS-SART is the same as that for the exemplified AlS-buoy, no further example is deemed necessary.

Claims

Claims: 1. ) A passive AIS buoy or AIS-SART comprising: means for determining a location of the buoy or SART; means for receiving an AIS signal from another AIS source; means for transmitting an AIS signal; and means for reacting to receipt of said AIS signal from another AIS source; wherein, the passive AIS buoy or AIS-SART is capable of receiving said AIS signal from said another AIS source and reacting to that by transmitting an AIS signal comprising the location of the buoy or SART.
2. ) A passive AIS buoy or AIS-SART as claimed in claim 1, further comprising solar and/or wind power generation, such that the buoy or SART is capable of working indefinitely without external recharging.
3. ) A passive AIS buoy or AIS-SART as claimed in claim 1 or claim 2, wherein the passive AIS buoy or AIS-SART is capable of transmitting an AIS signal comprising the location and identification of the buoy or SART.
4. ) A passive AIS buoy or AIS-SART as claimed in any preceding claim comprising means for receiving an IMO orMMSI number from said another AIS source.
5. ) A passive AIS buoy or AIS-SART as claimed in claim 4 comprising means for validating an IMO or MMSI number from said another AIS source before reacting thereto.
6. ) A passive AIS buoy or AIS-SART as claimed in any preceding claim, wherein the means for determining a location of the buoy or SART is GPS, GLONASS, Galileo, and/or BeiDou satellite navigation systems.
7. ) A passive AIS buoy or AIS-SART as claimed in any preceding claim comprising means for altering a transmit interval time, T, between respective transmissions following receipt of said AIS signal from said another AIS source.
8. ) A passive AIS buoy or AIS-SART as claimed in any preceding claim comprising: means for altering a/the transmit interval time, T, between respective transmissions depending upon a speed of movement of the AIS buoy or AIS-SART itself and/or a speed of movement of said another AIS source; or means for altering a/the transmit interval time, T, between respective transmissions depending upon the amount of IMO and/or MMSI numbers received.
9. ) A passive AIS buoy or AIS-SART as claimed in claim 8 comprising means for altering a/the transmit interval time, T, between respective transmissions depending upon a relative closing speed of the AIS buoy or AIS-SART and said another AIS source, or their relative diverging speed.
10. ) A passive AIS buoy or AIS-SART as claimed in any preceding claim, wherein the buoy or SART comprises: a GPS receiver; two AIS receivers, one for each AIS channel; and an AIS transmitter.
11. ) A passive AIS buoy or AIS-SART, substantially as herein disclosed, with reference to the accompanying Figure 1,2 or 3 of the accompanying drawings and/or any example described herein.
12. ) A method for operating a passive AIS buoy or AIS-SART, the method comprising: determining a location of the buoy or SART and receiving an AIS signal from another AIS source; or receiving an AIS signal from another AIS source and determining a location of the buoy or SART; and reacting to receipt of the AIS signal from said another AIS source by transmitting an AIS signal comprising the location of the buoy or SART.
13. ) A method as claimed in claim 12 comprising transmitting an AIS signal comprising the location and identification of the buoy or SART.
14. ) A method as claimed in claim 12 or claim 13 comprising receiving an IMO or MMSI number from said another AIS source.
15. ) A method as claimed in claim 14 comprising validating the IMO or MMSI number from said another AIS source before transmitting.
16. ) A method as claimed in any one of claims 12 to 15 comprising altering a transmit interval time, T, between respective transmissions following receipt of the AIS signal from said another AIS source.
17. ) A method as claimed in any one of claims 12 to 16 comprising: altering a/the transmit interval time, T, between respective transmissions depending upon a speed of movement of the AIS buoy or AIS-SART itself and/or a speed of movement of said another AIS source; or altering a/the transmit interval time, T, between respective transmissions depending upon the amount of IMO and/or MMSI numbers received.
18. ) A method as claimed in claim 17 comprising altering the transmit interval time, T, between respective transmissions depending upon a/the relative closing speed of the AIS buoy or AIS-SART and said another AIS source, or their relative diverging speed.
19. ) A method as claimed in any one of claims 16 to 18 comprising shortening and/or maintaining the transmit interval time, T, if the AIS buoy or AIS-SART and/or said another AIS source is/are moving quickly, or the AIS buoy or AIS-SART and said another AIS source are moving closer together.
20. ) A method as claimed in any one of claims 16 to 19 comprising lengthening and/or maintaining the transmit interval time, T, if the AIS buoy or AIS-SART and/or said another AIS source is/are moving slowly, or the AIS buoy or AIS-SART and said another AIS source are moving further apart.
21. ) A method as claimed in any one of claims 12 to 20 comprising recharging an internal battery solely through means of solar and/or wind power generation conducted on the buoy or SART.
22. ) A method for operating a passive AIS buoy or AIS-SART, substantially as herein disclosed, with reference to Figure 4 or the accompanying description and/or any example described herein.
23. ) A method for conserving power in a buoy or SART, the method comprising: checking an internal battery level of the buoy or SART; if the battery level is below a threshold, and no signal has been received from another signal source, placing a means for transmitting and/or a means for determining a location of the buoy or SART in standby; remaining in standby until either: upon subsequently checking the battery level, the level is above the threshold; or a signal is received from said another signal source; and transmitting a signal comprising the location of the buoy or SART.
24. ) A method as claimed in claim 23, wherein if the battery level is above the threshold, transmitting a signal comprising the location of the buoy or SART every transmit interval time, Ti.
25. ) A method as claimed in claim 23 or claim 24, wherein if the battery level is below the threshold, independently of any transmitting following receipt of an/said signal from said another signal source, transmitting a signal comprising the location of the buoy or SART every transmit interval time, T2, where T2 > T1.
26. ) A method for conserving power in a buoy or SART, the method comprising: checking an internal battery level of the buoy or SART and setting a transmit interval time, T1, at which transmit interval time the buoy or SART will transmit a location of the buoy or SART; if the battery level is below a threshold, and no signal has been received from another signal source, setting a transmit interval time, T2, in which T2 > T1; if a signal is received from said another signal source, independently of either transmit interval time, T1 orT2, transmitting a signal comprising the location of the buoy or SART.
27. ) A method as claimed in any one of claims 23 to 25 or claim 26, further comprising transmitting a signal comprising the location and identification of the buoy or SART.
28. ) A method as claimed in any one of claims 23 to 25 or any one of claims 25 to 26, wherein the method is a method for conserving power in an AIS buoy or AIS-SART, and the buoy or SART is capable of receiving and/or transmitting AIS signals.
29. ) A method for conserving power in an AIS buoy or AIS-SART, substantially as herein disclosed, with reference to the accompanying description or Figure 4, and/or any example described herein.
30. ) A data carrier, disk, chip, computer, tablet or the like programmed to implement the method of any one of claims 12 to 22 or claims 23 to 29, or a piece of software stored on any such device coded to implement the method of any one of claims 12 to 22 or claims 23 to 29.
31. ) A passive AIS buoy or AIS-SART comprising: means for receiving an AIS signal from another AIS source; means for transmitting an AIS signal; and means for reacting to receipt of said AIS signal from another AIS source; wherein, the passive AIS buoy or AIS-SART is capable of receiving said AIS signal from said another AIS source and reacting to that by transmitting an AIS signal comprising an identification of the buoy.
32. ) A passive buoy or SART comprising: means for determining a location of the buoy or SART; means for receiving a signal from another signal source; means for transmitting a signal; and means for reacting to receipt of said signal from another signal source; wherein, the passive buoy or SART is capable of receiving the signal from said another signal source and reacting to that by transmitting a signal comprising the location of the buoy or SART.
33.) A method for operating a passive buoy or SART, the method comprising: determining a location of the buoy or SART and receiving a signal from another signal source; or receiving a signal from another signal source and determining a location of the buoy or SART; and reacting to receipt of the signal from said another signal source by transmitting a signal comprising the location of the buoy or SART.