WO2021198629A1

WO2021198629A1 - Vessel location monitoring system

Info

Publication number: WO2021198629A1
Application number: PCT/GB2020/052168
Authority: WO
Inventors: Vincent Geake
Original assignee: Digital Business Strategy Ltd
Priority date: 2020-03-30
Filing date: 2020-09-09
Publication date: 2021-10-07

Abstract

A vessel monitoring system for locating on a secondary vessel, the vessel monitoring system configured to receive an AIS message from a primary vessel, determine, based at least in part on the received AIS message, a distance between the primary vessel and the secondary vessel, and output an alert signal for alerting crew on the primary vessel in response to determining that a distance between the primary vessel and the secondary vessel exceeds a threshold distance.

Description

VESSEL LOCATION MONITORING SYSTEM

Field

The present disclosure relates to a vessel location monitoring system.

Background

An individual vessel (hereafter occasionally referred to as a primary vessel or a first vessel) such as a yacht is often operated in association with one or more other waterborne vessels, for example a tender, launch or jetski (hereafter occasionally referred to as a secondary vessel or a second vessel). The secondary vessel may be used to service the primary vessel, to assist with moving people from the primary vessel to shore at a destination, or to enable people to explore the local area more easily. Such tenders or other secondary vessels may be located on the yacht, such as carried in davits, lifted on deck, or stored in internal ‘garages’ for safe transit between destinations.

Secondary vessels such as tenders are sometimes instead towed behind the primary vessel such as the yacht. While there are crew on the yacht, the tender may be un crewed. However, tenders are at risk of damage or loss when being towed, particularly at higher speeds, in rougher sea conditions, and by night. Incidents include loss due to failure of the towing system (such as lines, hawsers and/ or attachment points) as a result of high load, chafe or inadequate care, and the subsequent inability of the crew on the yacht or a salvage vessel to locate and/or recover the tender. There is a desire to monitor for safety and operational purposes a secondary vessel such as a tender being towed by, or otherwise following, a primary vessel such as a yacht.

Summary

According to a first aspect of the present invention, there is provided a vessel monitoring system for locating on a secondary vessel, the vessel monitoring system configured to receive an AIS message from a primary vessel; determine, based at least in part on the received AIS message, a distance between the primary vessel and the secondary vessel; and output an alert signal for alerting crew on the primary vessel in response to determining that a distance between the primary vessel and the secondary vessel exceeds a threshold distance. The vessel monitoring system may be configured to determine the distance between the primary vessel and the secondary vessel by: determining a position of the primary vessel based on position information comprised in the AIS message; determining a position of the secondary vessel based on a signal received from a satellite navigation system receiver located on the secondary vessel; and determining the distance between the position of the primary vessel and the position of the secondary vessel.

The satellite navigation system receiver may be a GPS receiver. The GPS receiver may be comprised in an AIS transceiver located on the secondary vessel.

Outputting the alert signal may cause activation of a light coupled to the vessel monitoring system and located on the secondary vessel.

The light may be a strobe light.

The light may be a navigation light. Outputting the alert signal may modify the behaviour of a beacon coupled to the vessel monitoring system and located on the secondary vessel.

Modifying the behaviour of the beacon may comprise activating the beacon. Modifying the behaviour of the beacon may comprise increasing a frequency at which the beacon outputs a wireless signal.

The beacon may be a satellite beacon. The beacon may comprise an AIS transceiver coupled to the vessel monitoring system and outputting the alert signal causes the AIS transceiver to transmit an AIS message.

Outputting the alert signal may cause the AIS transceiver to transmit the AIS message by causing the AIS transceiver to leave a silent mode of the AIS transceiver. Causing the AIS transceiver to leave a silent mode may comprise causing activation of a relay coupled to the vessel monitoring system.

The vessel monitoring system may be further configured to cause the AIS transceiver to leave silent mode in response to detection of a software error within the secondary vessel monitoring system.

The vessel monitoring system may be further configured to cause the AIS transceiver to leave silent mode in response to a power failure associated with the vessel monitoring system.

The vessel monitoring system may be further configured to cause the AIS transceiver to leave silent mode in response to the vessel monitoring system not receiving a further AIS message from the primary vessel within a predetermined period of time.

The AIS message transmitted by the AIS transceiver of the secondary vessel may comprise information indicative of a position of the secondary vessel.

The AIS message transmitted by the AIS transceiver of the secondary vessel may comprise a Type 18 position report.

The primary vessel may be a yacht and the secondary vessel may be a tender.

According to a second aspect of the present invention, there is provided a vessel monitoring system for locating on a primary vessel, the vessel monitoring system configured to: receive position information associated with a secondary vessel from an AIS message transmitted by the secondary vessel to the primary vessel; receive position information associated with the primary vessel; determine a distance between the primary vessel and the secondary vessel based on the position information associated with the primary vessel and the position information associated with the secondary vessel; and output an alarm condition based on the determined distance.

The vessel monitoring system of the second aspect maybe further configured to: compare the determined distance to a predetermined threshold distance; and output the alarm condition in response to determining that the distance exceeds the predetermined threshold distance, wherein the alarm condition provides an indication that the second vessel is adrift from the first vessel.

The vessel monitoring system of the second aspect maybe further configured to: compare the determined distance to a predetermined threshold distance; and output the alarm condition in response to determining that the distance is less than the predetermined threshold distance, wherein the alarm condition provides an indication of a system failure aboard the secondary vessel. Outputting an alarm condition may comprise outputting a signal causing at least one of a visible and an audio alarm to be output.

The position information associated with the primary vessel may be received from a GPS receiver.

The vessel monitoring system of the second aspect maybe further configured to: receive an identification token in the AIS message, the identification token identifying the secondary vessel; compare the identification token to one or more previously stored identification tokens; and only output the alarm condition if the received identification token corresponds to one or more of the previously stored identification tokens.

The received identification token may be an MMSI number.

The received identification token may uniquely identify the secondary vessel.

According to a third aspect of the present invention, there is provided a system comprising a vessel monitoring system according to the first aspect and a vessel monitoring system according to the second aspect. According to a fourth aspect of the present invention, there is provided a monitoring system for locating on a first vehicle, the monitoring system comprising a processing arrangement configured to: receive numerical data; determine a text string based on the numerical data; generate an NMEA sentence comprising the text string; and output the generated NMEA sentence.

The numerical data may comprise data received from one or more sensors. The numerical data may be associated with a second vehicle.

The monitoring system of the fourth aspect may be configured to determine the text string based on the numerical data by using a lookup table, wherein the lookup table comprises a plurality of predetermined text strings each having associated predetermined numerical data.

The numerical data may not be derived from an AIS message.

The NMEA sentence maybe an NMEA 0183 sentence.

The NMEA sentence may be an NMEA 2000 sentence. The NMEA sentence may be an NMEA AIVDM sentence comprising the text string.

The NMEA AIVDM sentence may correspond to an AIS Type 12 message or an AIS Type 14 message. The monitoring system of the fourth aspect may be further configured to output the generated NMEA sentence to another apparatus.

The other apparatus maybe a chartplotter. The first vehicle may be a marine vessel.

Brief Description of the Drawings

Exemplary embodiments of the present invention are described with reference to the accompanying drawings, in which:

Figure 1 is a schematic illustration of an AIS system;

Figure 2 is a schematic illustration of a primary vessel monitoring system according to aspects of the present invention aboard a primary vessel and a secondary vessel monitoring system according to aspects of the present invention aboard a secondary vessel; and Figure 3 is a schematic illustration of a secondary vessel monitoring system such as the secondary vessel monitoring system of Figure 2 according to aspects of the present invention, in relation to a primary vessel and a secondary vessel. Detailed Description

Aspects of the present disclosure relate to monitoring systems for vehicles such as marine vessels. A secondary vessel (also known herein as an associated vessel or second vessel) such as a tender may be operating under control of its own crew, or may be un crewed and under tow by a primary vessel (also known as a main vessel or first vessel) such as a yacht. Aspects of the present disclosure may provide the crew of the primary vessel with timely, actionable information to help them fulfil their task of monitoring and protecting the associated secondary vessel. In some examples, aspects of the present disclosure may provide a system that allows the crew of the primary vessel to be alerted when the secondary vessel drifts from the primary vessel, for example following a towline between the primary vessel and the secondary vessel breaking while the primary vessel is towing the secondary vessel.

There exists an internationally standardised marine vessel location reporting system known as the Automatic Identification System (AIS), which provides for the regular broadcast of position reports from vessels using an AIS transceiver over VHF (very high frequency) radio. The reports are sent as AIS messages and can be received by any nearby vessel or shore station also having a corresponding AIS transceiver. Having received the position report in the AIS message, the position of the broadcasting vessel(s) as indicated by the position report can then be typically displayed on an electronic chartplotter on the receiving vessel, to help the crew of the receiving vessel manage their vessel safely.

There are a number of predetermined types of AIS message that can be broadcast according to the AIS standards. These messages may relate to the position of the vessel: one such AIS message type is a ‘Type 1’ message, also known as a ‘Position Report’ broadcast by Class A AIS transceivers as normally fitted to larger vessels like the yacht, another is a ‘Type 18’ message, also known as a ‘Standard Class B Equipment Position Report’ broadcast by Class B AIS transceivers as normally fitted to smaller vessels like the tender. Other messages may be text messages: one such AIS message type is a ‘Type 12’ message, also known as an ‘Addressed safety related message’, which may be sent to and acknowledged by an addressed vessel. Another AIS message type is a ‘Type 14’ message, also known as a ‘Safety related Broadcast Message’, which may be broadcast to all vessels in the vicinity of the broadcasting vessel.

The AIS system uses the international Maritime Mobile Service Identity (MMSI) as the identifier for the broadcasting vessel in an AIS message. A separate AIS message Type 24 (‘Static data report’) can be used to associate a vessel name with a specific MMSI.

Secondary vessels such as tenders are very likely to be fitted with a ‘Class B’ AIS transceiver, while ‘Class A’ AIS transceivers are generally used aboard bigger vessels such as tankers. Under AIS regulations, Class B AIS transceivers automatically send a position report once every three minutes when the vessel on which they are installed is travelling at a boatspeed of less than 2 knots, and once every thirty seconds when at a boatspeed of greater than 2 knots. Class A AIS transceivers automatically send a position report every 2 to 10 seconds when under way.

Even though a secondary vessel such as a tender may be fitted with an AIS transceiver, certain maritime regulations stipulate that a secondary vessel should not transmit AIS messages using its AIS transceiver while it is under tow by a primary vessel. Marine electronics equipment such as chartplotters, AIS transceivers and navigation and instrument systems, are generally equipped with interfaces according to the National Marine Electronics Association (NMEA) standards. These standards define multiple aspects of the interface including the structure of information messages to be sent between equipment. There are two main sets of NMEA standards, the first being the widely used NMEA 0183, while the second is NMEA 2000, which is a newer standard. In many cases, marine electronics equipment will be provided with interfaces for both standards in order to simplify installation on a range of vessels of different ages. The structure for information exchange is similar for both the NMEA 0183 and NMEA 2000 standards, so for simplicity, the more widely used NMEA 0183 standard is generally referred to throughout the present disclosure. Nevertheless it should be understood that NMEA 2000 may be used to replace NMEA 0183 throughout this disclosure wherever appropriate. Several manufacturers, for example Yacht Devices Ltd, supply ‘gateway products to assist with interconnection. Figure 1 illustrates an exemplary AIS system too. Throughout this disclosure, like reference numerals refer to like elements. Figure 1 shows a first vessel 110 (also known as a primary vessel) having an AIS transceiver 112 and a chartplotter 114. An AIS transceiver 112 will typically include an internal GPS receiver (not shown) to provide position and navigation information about the vessel 110 on which it is installed. A second vessel 120 (also known herein as a secondary vessel or associated vessel) also having an AIS transceiver 122 and possibly a chartplotter 124 may be in the vicinity of the first vessel 110. The first vessel 110 may transmit one or more AIS messages over a VHF channel 105 using its AIS transceiver 112. The AIS message may include information such as a position of the first vessel 110, for example a position obtained by the GPS receiver. The one or more AIS messages may be received by the AIS transceiver 122 of the second vessel 120. Information derived from the one or more AIS messages received by the AIS transceiver 122 of the second vessel 120, such as the position of the first vessel 110 or the closest future point of approach of the two vessels 110, 120, may be displayed using the chartplotter 124 of the second vessel 120. A crewmember on the second vessel 120 may therefore be able to view a representation of the position of the first vessel 110 on the chartplotter 124 of the second vessel 120.

The one or more AIS messages transmitted by the first vessel 110 may also be received by AIS transceivers of other vessels 130 in the vicinity or of shore stations 140 in the vicinity of the first vessel 110. Furthermore, the AIS transceiver 112 of the first vessel 110 may also be able to receive one or more AIS messages transmitted by the second vessel 120, other vessels 130 or shore station 140, and output information derived from the messages on its own chartplotter 114, in a similar fashion to the second vessel 120.

On each vessel 110, 120, the AIS transceivers 112,122 and the corresponding chartplotters 114,124 generally communicate using an NMEA standard. This may be the NMEA 0183 standard or the NMEA 2000 standard, as discussed previously. Figure 1 shows a communication channel 116 between the AIS transceiver 112 and the chartplotter 114 of the first vessel 110. A similar communication channel 126 may be between the AIS transceiver 122 and the chartplotter 124 of the second vessel 120.

External AIS messages are received by the AIS transceiver 112 over the VHF channel 105. The external AIS messages, or data/information derived from the external AIS messages, are transmitted from the AIS transceiver 112 to the chartplotter 114 using NMEA 0183 or NMEA 2000 messages, or NMEA ‘sentences’, which have a structure defined in the NMEA 0183 standard or the NMEA 2000 standard. The AIS NMEA messages sent from the AIS transceiver 112 to the chartplotter 114 may be known as internal AIS Rx messages. The communication channel 116 between the AIS transceiver 112 and the chartplotter 114 over which the NMEA messages are received is typically provided by a wired connection, but could be a wireless connection. The AIS transceiver 112 may have an NMEA interface through which the AIS NMEA messages are sent to/received from the communication channel 116. Similarly, the chartplotter 114 may have an NMEA interface through which the AIS NMEA messages are sent to/received from the communication channel 116.

The Internal AIS Rx messages are typically implemented as specific sentences within the NMEA 0183 or 2000 structure. The AIS transceiver 112, 122 outputs ‘AIS NMEA messages’ on the NMEA interface corresponding to the received AIS messages. Using the NMEA 0183 standard, this will typically be as an NMEA AIVDM sentence, with the fields formatted and encapsulated for different message types, for example a received Type 12 AIS message will be output as an NMEA AIVDM sentence of type 12, and a received Type 14 AIS message will be output as an NMEA AIVDM sentence of type 14.

In addition, the AIS transceiver 112, 122 may output its own location on the NMEA interface as an NMEA AIVDO message. Using the NMEA 2000 standard, the NMEA output will typically be one of a set of different PGN formats, for example a received Type 12 message will be output as a NMEA 2000 PGN 129801, and a received Type 14 message will be output as a NMEA 2000 PGN 129802. For simplicity, the NMEA 0183 standard AIVDO & AIVDM sentences are generally referred to below, but a person experienced in the field will be capable of relating this to implementation by different manufacturers and when using NMEA 2000. For example, for a vessel 110, 120 with marine electronics using NMEA 0183, the AIS message types received by the AIS transceiver 112, 122 are delivered to the chartplotter 114, 124 over an NMEA 0183 interface using the AIVDM sentence set defined by the National Marine Electronics Association, which typically reflect the AIS message type structure. Navigation information relating to the vessel 110, 120 on which the AIS transceiver 112, 122 and chartplotter 114, 124 are installed is typically captured by a GPS receiver integrated into the AIS transceiver 112, 122, and linked with vessel data (including e.g. MMSI) programmed into the AIS transceiver 112, 122, to generate NMEA 0183 sentences with the AIVDO sentence set and sent to the chartplotter 114, 124. Internal AIS Tx messages, typically using the NMEA AIVDM sentence set, may be sent for example from the chartplotter 114 of the first vessel 110 to the AIS transceiver 112 of the first vessel 110 across communication channel 116, typically implemented as a wired NMEA connection.

AIS regulations provide that when an AIS transceiver, for example the AIS transceiver 122 of the second vessel 120, is a Class B transceiver, it should accept the external input if available, typically from a gyro-compass, of the ‘True Heading’ value (ie relative to geographic north) of the second vessel 120, for example over an NMEA 2000 interface according to the NMEA 2000 PGN 127250 Vessel Heading with ‘True’ indicated. It should also include a value (represented as a 9-bit field) for True Heading in Type 18 Class B Equipment Position Reports which it broadcasts. The True Heading value included in such a Type 18 message should be reported as a value from 0-359 when such a True Heading value is input, and a value of 511 if a True Heading value is not input. Vessels 110, 120 carrying Class B transceivers are not required to be equipped with a gyro-compass, and typically are not so equipped.

Figure 2 shows a secondary vessel monitoring system 220 (also known as a second vessel monitoring system 220) in accordance with some aspects of the present invention and a primary vessel monitoring system 210 (also known as a first vessel monitoring system 210) in accordance with some aspects of the present invention. As should be clear throughout this disclosure, not all of the features of the secondary vessel monitoring system 220 and the primary vessel monitoring system 210 illustrated in Figure 2 may be required. In other words, some of the features of Figure 2 are optional in certain aspects of the present disclosure, as should be apparent from the disclosure.

Figure 2 shows a first vessel 110 (primary vessel) and a second vessel 120 (secondary vessel), which maybe similar to the first vessel 110 and second vessel 120 described previously in relation to Figure 1. The second vessel 120 may be in the vicinity of the first vessel 110. The first vessel 110 maybe a primary vessel such as a yacht or ship. The second vessel 120 may be a tender, for example used for servicing or supporting the first vessel 110, or may be a chase-boat, jet ski or any other vessel, for example typically used for recreational purposes. In some examples, the second vessel 120 is being towed by the first vessel 110 using a towline 250 coupled between them. An optional towline sensor 260 may detect information associated with the towline 250. In other examples, -lithe second vessel 120 is operated independently of the first vessel 110 without being towed, for example under its own power. The second vessel 120 may be manned or unmanned. The first vessel 110 has an AIS transceiver 112 and a chartplotter 114 as described previously, together with optional other electronic systems such as a navigation & instrumentation system 650 and an alarm system 750. A navigation & instrumentation system 650 may comprise one or more sensors 652, a user interface 651 comprising one or more displays with user controls, and one or more electronic interfaces 671 typically according to an NMEA standard.

The alarm system 750 may comprise one or more sensors 752 and may comprise a user interface 751 which may comprise indicator lights and/ or buzzers, buttons, or touchscreen displays. The alarm system 750 will therefore typically have a variety of information interfaces 672 for communicating data/ signals, and optionally it may also include an aggregator device 753 to report multiple sensor 752 outputs on a single interface 672 (e.g. an NMEA standard or an RS-232 serial interface). The alarm system 750 may also exchange data/signals with the navigation & instrumentation system 650, and the information accessed via associated electronic interfaces 671.

The alarm system 750, the navigation & instrumentation system 650 and the chartplotter 114 may be closely integrated and/ or may be implemented as one or more separate devices and/or software modules. The alarm system 750 maybe connected (e.g. by a network) for example to the navigation & instrumentation system 650, which may provide audible & visible indication of alarms within its user interface 651, and may generate further alarms based on processing of data from navigation & instrumentation sensors 652. Information from the alarm system 750 and the navigation & instrumentation system 650 may be shared so that alarm information is also available for example by intercepting that connection (e.g. Ethernet) or across interface 671, in addition to across interface 672.

The AIS transceiver 112 and / or the chartplotter 114 may have a display 118 for providing a visual output, such as a visual indication of information associated with the first vessel 110 or the second vessel 120. The chartplotter 114 may have an audio transducer/ speaker 119 for providing an audio output. The AIS transceiver 112 may be configured to transmit information to the chartplotter 114 via a communication channel n6a using the NMEA 0183 or NMEA 2000 standard, for example, as discussed previously.

The second vessel 120 may also have an AIS transceiver 122 as described previously, for transmitting AIS messages to the AIS transceiver 112 of the first vessel 110 over a VHF channel 105, and/or receiving AIS messages transmitted by the AIS transceiver 112 of the first vessel 110 over the VHF channel 105.

A first vessel monitoring system 210 is located on the first vessel 110. The first vessel monitoring system 210 can be used for monitoring various aspects of the first vessel 110 and/or second vessel 120. The first vessel monitoring system 210 may comprise a processing arrangement 212 for performing any method steps such as processing, determining, receiving or outputting steps described herein. The processing arrangement 212 maybe any suitable processing arrangement 212 for example comprising as one or more processors or control logic, and may include one or more memories (not shown) for storing program operating code, data or the like. As an example, the processing arrangement 212 may comprise an STM32F407 microprocessor from ST Microelectronics (an ARM Cortex M4 device). The processing arrangement 212 may execute the program operating code stored on the one or more memories in order to perform any of the method steps disclosed herein.

The first vessel monitoring system 210 may further comprise a power supply 214 such as a battery or generator for supplying power to the components of the first vessel monitoring system 210. The first vessel monitoring system 210 may further comprise a user interface 217 which may comprise, for example, one or more indicators, buttons, keyfobs, and/or touch screens, and/or an interface to a personal mobile device for example a webapp served by the user interface 217 or an interface to an app installed on a personal mobile device (e.g. smartphone/tablet). The first vessel monitoring system 210 may be a computing device/ apparatus that is separate from the AIS transceiver 112, but in other examples maybe comprised in the AIS transceiver 112 or chartplotter 114, or other electronic systems such as the navigation & instrumentation system 650 or alarm system 750. The first vessel monitoring system 210 may comprise a satellite navigation receiver such as a GPS receiver (not shown), for obtaining position/location information of the first vessel no. In some cases the GPS receiver may instead be comprised in the AIS transceiver 112, or may be separate to the first vessel monitoring system 210 and AIS transceiver 112. The first vessel monitoring system 210 may be configured to generate one or more AIS NMEA messages for outputting to the chartplotter 114, for example NMEA 0183 or NMEA 2000 messages. These might typically be NMEA ATVDM messages of Type 12 or 14. In some examples, the first vessel monitoring system 210 outputs the one or more NMEA messages via a communication channel 116b which is coupled to the communication channel 116a between the AIS transceiver 112 and chartplotter 114. In the case of a NMEA 0183 channel, as generally described for simplicity herein, the one or more NMEA messages output by the first vessel monitoring system 210 over channel 116b may be multiplexed with the one or more NMEA messages output by the AIS transceiver 112 over channel 116a using a multiplexer 170 installed in the communication channel 116a. Such a multiplexer 170 may not be required for some implementations, for example where NMEA 2000 messages/an NMEA 2000 channel are used, since that is implemented as a bus connection. In some examples the multiplexer 170 is comprised in the first vessel monitoring system 210. Additionally, or alternatively, the first vessel monitoring system 210 may output the one or more generated NMEA messages to the chartplotter 114 via a separate communication channel n6d, rather than via channel 116a and the multiplexer 170.

In some examples, the first vessel monitoring system 210 may receive NMEA 0183 or NMEA 2000 messages from the AIS transceiver 112. In some examples this may be from the communication channel 116a between the AIS transceiver 112 and the chartplotter 114, via the multiplexer input 170 and communication channel 116b.

In some examples, communication channel 116a between the AIS transceiver 112 and chartplotter 114 does not exist. Instead the first vessel monitoring system 210 receives NMEA 0183 or NMEA 2000 messages from the AIS transceiver 112 via a communication channel 116c between the AIS transceiver 112 and first vessel monitoring system 210, and outputs NMEA 0183 or NMEA 2000 messages via the communication channel n6d to the chartplotter 114. The first vessel monitoring system 210 may modify or delete the one or more messages received from the AIS transceiver 112 and transmit the modified messages to the chartplotter 114 via channel n6d as described previously. Additionally some of the messages received by the first vessel monitoring system 210 from the AIS transceiver 112 via the channel 116c may be output from the first vessel monitoring system 210 via communication channel n6d without being modified and/or deleted. In other words, some messages output by the AIS transceiver 112 may be transmitted to the chartplotter 114 via the first vessel monitoring system 210. The first vessel monitoring system 210 may also generate one or more new messages using various additional information sources as described previously, such as user interface 217, and/or alarm system 750, and/or navigation & instrumentation system 650. The first vessel monitoring system 210 may be connected to receive AIVDM messages from the chartplotter 114. These messages may be sent to the AIS transceiver 112 via communication channel n6e which may be observed by the first vessel monitoring system 210, or else may be sent to the first vessel monitoring system 210 via a separate communication channel n6f. In some examples, channels n6d and n6f may be the same channel (e.g. use the same cable). In some examples, channels n6e and 116a may be the same channel (e.g. use the same cable).

A second vessel monitoring system 220 according to aspects of the present disclosure is to be located on the second vessel 120. The second vessel monitoring system 220 may comprise a processing arrangement 221 and optionally one or more sensing systems 222. The processing arrangement 221 may be for performing any method steps such as processing, determining, receiving or outputting steps described herein and may be any suitable processing arrangement such as comprising one or more processors or control logic, and one or more memories for storing program operating code, data or the like coupled to the one or more processors or control logic, similar to the previously described processor arrangement 212. As an example, the processing arrangement 222 may comprise an STM32F407 microprocessor from ST Microelectronics (an ARM Cortex M4 device).The processing arrangement 221 may execute the program operating code stored on the one or more memories in order to perform any of the method steps disclosed herein.

The sensing systems 222 may include, but are not limited to, a water level sensing system 223, a bilge pump sensing system 224, a battery monitoring system 225, a vessel attitude sensing system 440 and an intruder sensing system (not shown). The secondary vessel monitoring system 220 may also comprise a satellite navigation receiver such as GPS receiver 227, which can be used to determine a geographical location/position of the second vessel via receipt of a GPS signal. The secondary vessel monitoring system 220 may also comprise an AIS transceiver 122, which can be used to transmit AIS messages from the second vessel 120 to AIS transceiver 112 of the first vessel 110 over VHF channel 105, as discussed previously. Figure 2 shows the GPS receiver 227 and AIS transceiver 122 as part of the secondary vessel monitoring system 220, however the invention is not limited as such, and one or both of the GPS receiver 227 and AIS transceiver 122 may be located on the second vessel 120 separate from the secondary vessel monitoring system 220 and in communication with the secondary vessel monitoring system 220 via a wired or wireless connection. In some examples the GPS receiver 227 may be comprised in the AIS transceiver 122.

The second vessel 120 may also include a wireless transmitter 228 configured to transmit wireless signals. The wireless signals are transmitted over a wireless channel 229 and are received by a corresponding wireless receiver 216 of the first vessel 110, wherein the wireless receiver 216 may form part of the first vessel monitoring system 210 or be connected to the first vessel monitoring system 210 by a wired or wireless connection.

The second vessel 120 may further comprise one or more output systems 230, such as a beacon 231, a light 232, or the transmitter section of the AIS transceiver 122. The beacon 231 may comprise a cellular beacon for outputting a signal to a cellular network 341 or a satellite beacon for outputting a signal to a satellite network, for example. The light 232 may be a strobe light, but any other high-powered or highly visible light 232 that can be used to alert crew in the first vessel 110 of a status or the location of the second vessel 120 may be used, such as a navigation light. The transmitter section of the AIS transceiver 122 may be externally enabled and disabled, typically via a wired connection commonly known as ‘stealth mode’ or ‘silent mode’, as discussed later. The output systems 230 could also comprise a loudspeaker or the like (not shown).

The processing arrangement 221 of the secondary vessel monitoring system 220 maybe configured to receive signals output from the GPS receiver 227 and output information/data corresponding to the signals via the AIS transceiver 122 or the wireless transmitter 228. This data maybe received by the first vessel 110 using its own AIS transceiver 112 or the wireless transceiver 216. The first vessel monitoring system 210 is configured to receive information associated with the first vessel 110 and/or second vessel 120 and any user input information via the user interface 217, process the information, and then may output some or all of text messages pre-defmed to correspond to the processed information sent to the chartpl otter 114 (typically in the form of NMEA AIVDM sentences of Type 12

‘Addressed Safety-Related Message’ or Type 14 ‘Safety-related Broadcast messages’), numeric data corresponding to the processed information sent to the navigation & instrument system 650 (typically in the form of NMEA sentences for example the general NMEA 0183 XDR sentence), and alarm acknowledgement signals (e.g. to silence or cancel an alarm) to the alarm system 750, for example for display or for activation of functions within such systems.

Data output by the first vessel monitoring system 210 may be sent by the first vessel monitoring system 210 as an AIS NMEA 0183 or NMEA 2000 message to the chartplotter 114 via communication channel n6d or 116b as discussed previously.

The sent NMEA 0183 or NMEA 2000 message may have been generated by the first vessel monitoring system 210, based on the received information associated with the first vessel 110 and/or second vessel 120. In some examples the sent NMEA 0183 or NMEA 2000 message maybe a NMEA 0183 or NMEA 2000 message that has been received by the first vessel monitoring system 210 from the AIS transceiver 112 and has then been modified based on the received information associated with the first vessel 110 and/ or second vessel 120 and output by the first vessel monitoring system 210 to the chartplotter 114. The NMEA message may have been modified to include the data corresponding to the processed information.

The information associated with the second vessel 120 may comprise information indicating a location of the second vessel 120, for example as determined by the GPS receiver 227 of the second vessel. The information associated with the first vessel 110 may be received by the first vessel monitoring system 210 from one or more systems on the first vessel 110, such as the chartplotter 114 via interface n6f, the navigation & instrumentation system 650 via interface 671, the alarm system 750 or individual sensors 752 via interface 672. The information associated with the first vessel 110 may comprise information indicating a location of the first vessel 110, for example as determined by a GPS receiver of the first vessel 110. According to AIS standards, a chartplotter 114 may process AIS messages received from the AIS transceiver 112 and present information to the user derived from the AIS messages. The chartplotter 114 may provide a visible output of the information, for example via a display 118. In addition or alternatively, the chartplotter 114 may provide an audible output of the information, for example via a speaker 119. The chartplotter 114 may in some cases output an audio or visual alarm. The chartplotter 114 may, for example, receive and display information from addressed or broadcast AIS messages (for example AIS Message Types 6, 8 or 25 etc.) or from emergency AIS messages (for example, Message Type 1 with ‘Navigation Status’ = 14). The chartplotter 114 may compare a vessel position reported in any AIS message, determine the range from its own location (e.g. obtained using a GPS receiver), and display an alarm if this drops below a set threshold “geo-fence”. In addition, the chartplotter 114 may generate and send, e.g. across channel n6f, one or more AIVDM messages.

According to an aspect of the present disclosure as illustrated in Figure 3, a first vessel 110 maybe towing a second vessel 120, such as an un-crewed associated vessel, and the crew may wish to be able to locate and recover the second vessel 120 quickly and easily, for example if the towline 250 connecting the two vessels becomes separated and the first vessel 110 and second vessel 120 drift apart.

In this example, a second vessel monitoring system 220 is installed on the second vessel 120. The second vessel monitoring system 220 is connected to the second vessel AIS transceiver 122. The second vessel monitoring system 220 may be any second vessel monitoring system 220 discussed previously, for example as discussed in relation to Figure 2. Processes carried out by the second vessel monitoring system 220 may be performed by the processing arrangement 221 of the second vessel monitoring system 220, as discussed previously. The second vessel monitoring system 220 is configured to receive a signal from the first vessel 110, the signal being indicative of a geographical location of the first vessel 110, such as geographical coordinates. The signal may comprise one or more AIS messages transmitted from an AIS transceiver 112 of the first vessel 110 as previously discussed and received via the AIS transceiver 122 of the second vessel 120. The one or more AIS messages comprise position information indicative of the geographical location of the first vessel 110, such as geographical coordinates of the first vessel 110. The one or more AIS messages transmitted by the AIS transceiver 112 of the first vessel 110 are received by the AIS transceiver 122 of the second vessel 120. The one or more AIS messages may be converted by the AIS transceiver 122 to an NMEA sentence comprising the information of the AIS message as discussed previously, such as an NMEA 1083 AIVDM sentence. The NMEA sentence comprises the position information. The converted NMEA sentence is then sent from the AIS transceiver 122 to the second vessel monitoring system 220.

Having received the AIS message from the first vessel 110 via the AIS transceiver 122 of the second vessel 120, the second vessel monitoring system 220 comprising the processing arrangement 221 determines a distance between the first vessel 110 and the second vessel 120 based on the signal received from the first vessel 110, that is the received AIS message. As an example, the second vessel monitoring system 220 may determine the distance between the first vessel and the second vessel by determining a geographical position of the first vessel 110 based on the position information (such as geographical coordinates) comprised in the received AIS message (or NMEA sentence). The second vessel monitoring system 220 may determine a geographical position of the second vessel 120 based on a signal received from a satellite navigation system receiver located on the second vessel 120, such as a GPS receiver 227 on the second vessel 120 as discussed previously. The GPS receiver 227 may be comprised in the second vessel monitoring system 220, the AIS transceiver 122, or elsewhere on the second vessel 120. The position of the second vessel 120 may be determined based on geographical coordinates output by the GPS receiver 227. Having determined the position of the first vessel 110 and the second vessel 120, the second vessel monitoring system 220 may determine the distance between the position of the primary vessel 110 and the position of the secondary vessel 120. The second vessel monitoring system 220 compares the determined distance between the first vessel 110 and the second vessel 120 to a predetermined threshold distance, for example a threshold distance stored in a memory of the second vessel monitoring system 220. In response to a determination that the determined distance is greater than the threshold distance, the second vessel monitoring system 220 outputs an alert signal, such as an electrical signal. The output alert signal may take a number of forms, singularly or in combination. As illustrated in Figure 3, the second vessel processing arrangement 221 of the second vessel monitoring system 220 may be coupled to a light located on the second vessel, more particularly a strobe light 232 as discussed previously. The alert signal may causes activation (e.g. switching on) of the stobe light coupled to the second vessel monitoring system 220. For example, the alert signal may be an electrical signal which causes switching of a relay (not shown), causing the light to switch from an ‘off state to an ‘on’ state. In other cases, the light may already be flashing at a low frequency and the alert signal instead causes the light to flash at a greater frequency than before. While a strobe light 232 is shown in Figure 3, the light may be another type of light such as a navigation light, for example. The light should be located on the second vessel 120, and be of such a luminosity, that it can be readily observed by crew aboard the first vessel 110 when the first vessel 110 and second vessel 120 are separated by the threshold distance. In some examples the strobe light 232 (or other light) is not present and can be replaced in Figure 3 by a different output system as discussed below.

For example, additionally or alternatively to the above, the alert signal may cause the behaviour of a beacon 231 located on the second vessel 120 and coupled to the second vessel monitoring system 220 to be modified. The beacon 23iomay be in addition to the strobe light 232 shown in Figure 3, or be in place of the strobe light 232. The beacon 231 maybe a satellite beacon 231a as discussed previously. The beacon 231 emits a wireless signal for assisting a crew aboard the first vessel in locating of the second vessel 120. The wireless signal maybe a radio signal, for example, and may comprise position coordinates of the second vessel 120.

In some examples, modifying the behaviour of the beacon may comprise activating the beacon 231 (e.g. switching it on). For example, the alert signal maybe sent by the second vessel monitoring system 220 via a wired or wireless connection to a switch such as a relay. The signal may cause the switch (relay) to move from opened to closed (or closed to opened), thereby causing the beacon 231 to be activated (switched on). In response to being activated, the beacon 231 emits a wireless signal to indicate that the second vessel 120 is adrift of the first vessel 110, the wireless signal may provide information regarding the location of the second vessel 120 allowing for the location of the second vessel 120 to be determined by the crew aboard the first vessel 110, or the second vessel 120 to otherwise be found. In some examples, modifying the behaviour of the beacon 231 comprises modifying the frequency at which the beacon 231 emits the wireless signal. For example, the beacon 231 may initially be configured to emit a wireless signal every twenty-four hours. However, receipt of the alert signal may cause the beacon 231 to instead emit a wireless locating signal every hour.

In one example, the beacon 231 may comprise the AIS transceiver 122, or a part of the AIS transceiver 122 such as the AIS transmitting function of AIS transceiver 122. The alert signal may cause the AIS transceiver 122 of the second vessel 120 to transmit an AIS message. For example, the alert signal may be an electrical signal which causes the AIS transceiver 122 to leave (exit) a silent mode of the AIS transceiver, also known as a stealth mode. When in the silent mode, the AIS transceiver 122 is unable to transmit any AIS messages. However once the AIS transceiver has left the silent mode, AIS messages may be allowed to be transmitted by the AIS transceiver 122. In an example, the alert signal may be sent by the second vessel monitoring system 220 via a wired or wireless connection to a switch such as a relay. In one position (open or closed), the relay may cause the AIS transceiver 122 to be in silent mode. In another position (closed or open), the relay may cause the AIS transceiver 122 to no longer be in silent mode, and therefore AIS messages may be transmitted. The signal may cause the relay to move from opened to closed (or closed to opened), thereby causing the AIS transceiver 122 to transition from being in silent mode to not being in silent mode.

As discussed previously, the AIS transceiver 122 may be configured to automatically and periodically send out an AIS message comprising information indicative of a position of the second vessel. The AIS transceiver 122 may be configured to automatically and periodically send out the AIS message comprising the information indicative of a position of the second vessel when not in silent mode, but be prevented from sending such an AIS message when in silent mode. In some examples, the AIS message maybe a Type 18 ‘Standard Class B Equipment Position Report’ message.

In some examples, the second vessel monitoring system 220 may be configured to cause the AIS transceiver 122 to leave silent mode in response to detection of a software error within the second vessel monitoring system 220. For example, the second vessel monitoring system 220 may be configured to determine when an error has occurred in some processing carried out by the second vessel monitoring system 220. In response to determining the error has occurred, the second vessel monitoring system 220 may be configured to cause the AIS transceiver 122 to leave silent mode by default. This may be achieved in any manner discussed previously, for example by activation of a relay.

In some examples, the second vessel monitoring system 220 may be configured to cause the AIS transceiver 122 to leave silent mode in response to a power failure associated with the second vessel monitoring system 220, for example where the power supply to the second vessel monitoring system 220 is interrupted. Again, this may be achieved in any manner discussed previously, for example by activation of a relay. In some examples, the second vessel monitoring system 220 may be configured to cause the AIS transceiver 122 to leave silent mode in response to the vessel monitoring system not receiving a further AIS message from the first vessel 110 within a predetermined period of time. In other words, the second vessel monitoring system 220 may expect to receive an AIS message from the first vessel 110 via the AIS transceiver 122 of the second vessel 120 within a predetermined period of time, such as every 10 seconds. The period of time may commence in response to receipt of the previous AIS message received from the first vessel 110. If, after receiving an AIS message from the first vessel 110, the second vessel monitoring system 220 does not receive another AIS message from the first vessel 110 within the predetermined time period then it may cause the AIS transceiver to leave silent mode through any manner described previously, such as by providing a signal to a relay.

Additionally or alternatively to the above, the alert signal may cause an audio alarm of the second vessel 120 to be activated. The audio alarm should be located on the second vessel 120, and be of such a volume that it can be readily heard by crew aboard the first vessel 110 when the first vessel 110 and second vessel 120 are separated by the threshold distance.

The second vessel monitoring system 220 may be further configured to cause the AIS transceiver 122 of the second vessel 120 to enter silent mode in response to receipt of a signal, for example in response to receipt of an AIS message from the first vessel 110. In particular, subsequent to switching the AIS transceiver 122 out of silent mode, the second vessel monitoring system 220 may receive a further AIS message from the first vessel 110. The second vessel monitoring system 220 may determine based on the further AIS message that the distance between the first vessel 110 and the second vessel

120 has decreased such that the distance is now below a predetermined threshold. In response, the second vessel monitoring system 220 may output a signal that causes the AIS transceiver to enter the silent mode, for example by deactivating the relay.

In some aspects of the present disclosure, a first vessel monitoring system 210 may be located on the first vessel 110. In response to the first vessel monitoring system 210 receiving information regarding the associated second vessel 120, such as an AIS message received from the second vessel 120, the first vessel monitoring system 210 may use location information regarding the second vessel 120 contained in the AIS message and provided as an AIVDM message from the AIS transceiver 112, combined with location information regarding the first vessel 110 provided as an AIVDO message to determine the distance between the first vessel 110 and the second vessel 120. If the distance exceeds a predetermined threshold distance fin a similar manner as discussed for the second vessel monitoring system 2.2.0) then the first vessel monitoring system 210 may output an alarm condition for the first vessel 110 being adrift. However, if the distance is below the threshold distance then the first vessel monitoring system 210 may output an alarm condition for a failure of the performance of the second vessel monitoring system 220 due for example to software error, power failure or absence of AIS messages received from the yacht. Outputting an alarm condition may comprise outputting a signal causing at least one of a visible and an audio alarm to be output by an appropriate audio transducer or light coupled to the monitoring system.

The first vessel monitoring system 210 may then cause to be performed one or more of activating an audible and/or visible alarm, displaying appropriate information to the crew (e.g. via user interface 217 or navigation & instrument system 650 or alarm system 750), identify Internal AIS Rx messages relating to that associated second vessel 120, for example AIS Rx messages sent from AIS transceiver 112, change or delete such Internal AIS Rx messages and/ or generates new Internal AIS Rx messages relating to that associated second vessel 120 for output to the chartplotter 114, in order to make appropriate information regarding the associated second vessel 120 and/ or towline 250 visible to crew on the chartplotter 114. The specific format of the new Internal AIS Rx message maybe customised to suit the functionality of specific chartplotters 114 which maybe installed on the first vessel 110, and maybe augmented with an audible and/or visible alarm to draw attention to the availability of new information on the chartplotter 114. The first vessel monitoring system 210 may be configured to receive an identification token in the AIS message received from the second vessel 120, the identification token identifying the second vessel 120. The identification token may be an alphanumeric token. The received identification token may be an MMSI number, for example. The received identification token may uniquely identify the second vessel 120 such that the second vessel 120 is the only vessel assigned with that particular token. The first vessel monitoring system 210 may be configured to compare the identification token received from the second vessel 120 to one or more identification tokens previously stored in the first vessel monitoring system 210, for example in a memory of the first vessel monitoring system 210. The one or more identification tokens previously stored in the first vessel monitoring system 210 may have been stored in the first vessel monitoring system 210 by a user such as a crewmember of the first vessel 110 and may correspond to one or more other vessels associated with the first vessel 110, such as the second vessel 120. The first vessel monitoring system 210 may be configured to only output the alarm condition if the received identification token corresponds to one or more of the previously stored identification tokens. In other words, the first vessel monitoring system 210 checks that the identification token received from the first vessel 110 matches or otherwise corresponds to an identification token already stored in the first vessel monitoring system 210. If this is the case, the first vessel monitoring system 210 may output the alarm condition as previously discussed. This can ensure an alarm condition is only output if the first vessel monitoring system 210 recognises the second vessel 120, to prevent false alarms.

Another aspect of the disclosure relates to a monitoring system for locating on a first vessel 110, second vessel 120, or another type of vehicle. That is, the monitoring system is to be fitted to the first vessel 110, second vessel 120 or other vehicle. The monitoring system maybe a first vessel monitoring system 210 as described previously, or a second vessel monitoring system 220 as described previously. The monitoring system comprises a processing arrangement 212, 221 as described previously in relation to the first vessel monitoring system 210 or the second vessel monitoring system 220, the processing arrangement 212, 221 configured to receive numerical data, determine a text string based on the numerical data, generate an NMEA sentence comprising the text string and output the generated NMEA sentence. The numerical data does not comprise a text string. The numerical data may comprise data received from one or more sensors discussed previously, such as sensors located on the first vessel no, the second vessel 210, or elsewhere, such as on a towline 250 coupled between the first vessel no and the second vessel 120. The numerical data may comprise data, for example, indicative of a speed, heading, angle, load or the like, which maybe associated with the first vessel no and/or the second vessel 210. In some examples, the numerical data is not derived from an AIS message. In particular, the numerical data has not been derived from a text string comprised in an AIS message received by the monitoring system. For example, the numerical data has not been derived from an AIS message sent from the first vessel no to the second vessel 210, or vice versa.

Having received the numerical data, the processing arrangement 212, 221 of the monitoring system is configured to determine a text string based on the numerical data, for example by converting the numerical data to a text string comprising ASCII alphabetical characters. In some examples this may be achieved using a lookup table stored in a memory of the monitoring system, wherein the lookup table comprises a plurality of predetermined text strings each having associated predetermined numerical data. The processing arrangement 212, 221 may identify predetermined numerical data in the lookup table that corresponds to the received numerical data. The processing arrangement 212, 221 may identify the predetermined text string that corresponds to the predetermined numerical data identified in the lookup table.

After determining the text string based on the numerical data, the processing arrangement generates an NMEA sentence comprising the text string. The NMEA sentence maybe an NMEA 0183 sentence or an NMEA 2000 sentence. In particular, the NMEA sentence may be an AIVDM sentence as discussed previously and as known in the art, the AIVDM sentence comprising the text string. The AIVDM sentence may correspond to an AIS Type 12 message or an AIS Type 14 message.

After generating the NMEA sentence comprising the text string, the processing arrangement 212, 221 outputs the generated NMEA sentence comprising the text string. For example, the monitoring system may output the generated NMEA sentence to another apparatus such as a chartplotter 114, 124 over a wired or wireless communication channel. The external apparatus such as the chartplotter 114, 124 may interpret the text string contained in the output NMEA message and may act accordingly, for example by displaying information corresponding to the text string on a display of the apparatus. Modern vessels may generate alarms for a wide variety of reasons and it is not readily apparent which alarm has been triggered and why. However, many of these vessels already have chartplotters with high resolution LCD screens installed for example at nav stations or at helm stations. An advantage of the aforementioned monitoring system for locating on a first vessel is that information associated with sensor outputs or the like can be displayed on those standard existing pieces of equipment such as chartplotters, without having to install additional alarm message displays. The above monitoring system can make use of the NMEA AIVDM message interface commonly implemented on chartplotters 114, 124 in order to provide integration with the AIS vessel identification and position reporting system for improved safety of navigation between multiple unknown vessels, including display of safety related messages from other unknown vessels. The invention re-purposes this message interface to enable the crew to fulfil other monitoring tasks for safety or operational monitoring of the vessel or of associated vessels, for example displaying the positions of other vessels 120, 130 associated with a first vessel 110, where the position information has been received by other communication channels than AIS channels (i.e. other than VHF channel 105), for example from a satellite; displaying information and warning messages related to a vessel 120 being towed by the first vessel 110; and displaying and acknowledging warning and alarm messages relating to the first vessel itself. The monitoring system may generate text messages as text strings embedded in AIVDM sentences to be displayed by a chartplotter 114 to the crew, for example using information which has been received by the AIS transceiver 112 over the AIS channel 105, and is output to the monitoring system by the AIS transceiver 112 in a numeric or binary form (i.e. not text), or has not been received over the AIS VHF channel 105 but via other communication channels.

Aspects of the present disclosure may help crew associated with marine vessels to monitor equipment and assets, however aspects may also be applicable in fields other than marine vessels, for example in automated or satellite assisted agriculture and earthworking. That is, while this disclosure generally relates to marine vessels, it may also apply to other vehicles such as agricultural vehicles, earthworking vehicles, and the like, particularly where electronic equipment is used which follows the NMEA interfacing standards. Therefore throughout this disclosure, where reference is made to a first vessel 110 and/ or a second vessel 120, it should be understood that the first vessel no and/or the second vessel 120 may not be marine vessels, but may instead be others type of vehicle such as an agricultural vehicle (e.g. a tractor) or an earthworking vehicle (e.g. an excavator). That is, aspects of the present disclosure may relate to a first vehicle no and a second vehicle 120.

Throughout this document, where reference is made to a “receiver”, it should be understood that the “receiver” may in fact be a “transceiver” (so can also act as a transmitter). Likewise, where reference is made to a “transmitter”, it should be understood that the “transmitter” may in fact be a “transceiver” (so can also act as a receiver). In some cases, where reference is made to a transceiver, it should be understood that the “transceiver” may in fact be a receiver and not a transmitter, or may be a transmitter and not a receiver, where appropriate.

Where reference is made to one electronic component or system being ‘coupled’ or ‘connected’ to another electronic component system, this coupling may be achieved through a wired electrical connection or a wireless connection as appropriate.

Although the invention has been shown and described according to the above embodiments, it would be appreciated by those skilled in the art that changes may be made to the subject matter described herein without departing from the present invention, the scope of which is defined in the claims.

Claims

1. A vessel monitoring system for locating on a secondary vessel, the vessel monitoring system configured to: receive an AIS message from a primary vessel; determine, based at least in part on the received AIS message, a distance between the primary vessel and the secondary vessel; and output an alert signal for alerting crew on the primary vessel in response to determining that a distance between the primary vessel and the secondary vessel exceeds a threshold distance.

2. The vessel monitoring system of claim l, wherein the vessel monitoring system is configured to determine the distance between the primary vessel and the secondary vessel by: determining a position of the primary vessel based on position information comprised in the AIS message; determining a position of the secondary vessel based on a signal received from a satellite navigation system receiver located on the secondary vessel; and determining the distance between the position of the primary vessel and the position of the secondary vessel.

3. The vessel monitoring system of claim 2, wherein the satellite navigation system receiver is a GPS receiver.

4. The vessel monitoring system of claim 3, wherein the GPS receiver is comprised in an AIS transceiver located on the secondary vessel.

5. The vessel monitoring system of any one of claims 1 to 4, wherein outputting the alert signal causes activation of a light coupled to the vessel monitoring system and located on the secondary vessel.

6. The vessel monitoring system of claim 5, wherein the light is a strobe light.

7. The vessel monitoring system of claim 5, wherein the light is a navigation light.

8. The vessel monitoring system of any of claims l to 4, wherein outputting the alert signal modifies the behaviour of a beacon coupled to the vessel monitoring system and located on the secondary vessel.

9. The vessel monitoring system of claim 8, wherein modifying the behaviour of the beacon comprises activating the beacon.

10. The vessel monitoring system of claim 8 or 9, wherein modifying the behaviour of the beacon comprises increasing a frequency at which the beacon outputs a wireless signal.

11. The vessel monitoring system of claim 8, 9 or 10, wherein the beacon is a satellite beacon.

12. The vessel monitoring system of claim 8, 9 or 10, wherein the beacon comprises an AIS transceiver coupled to the vessel monitoring system and outputting the alert signal causes the AIS transceiver to transmit an AIS message.

13. The vessel monitoring system of claim 12, wherein outputting the alert signal causes the AIS transceiver to transmit the AIS message by causing the AIS transceiver to leave a silent mode of the AIS transceiver.

14. The vessel monitoring system of claim 13, wherein causing the AIS transceiver to leave a silent mode comprises causing activation of a relay coupled to the vessel monitoring system.

15. The vessel monitoring system of claim 13 or 14, wherein the vessel monitoring system is further configured to cause the AIS transceiver to leave silent mode in response to detection of a software error within the secondary vessel monitoring system.

16. The vessel monitoring system of claim 13, 14, or 15 wherein the vessel monitoring system is further configured to cause the AIS transceiver to leave silent mode in response to a power failure associated with the vessel monitoring system.

17. The vessel monitoring system of any of claims 13 to 17, wherein the vessel monitoring system is further configured to cause the AIS transceiver to leave silent mode in response to the vessel monitoring system not receiving a further AIS message from the primary vessel within a predetermined period of time.

18. The vessel monitoring system of any of claims 12 to 17, wherein the AIS message transmitted by the AIS transceiver of the secondary vessel comprises information indicative of a position of the secondary vessel.

19. The vessel monitoring system of claim 18, wherein the AIS message transmitted by the AIS transceiver of the secondary vessel comprises a Type 18 position report.

20. The vessel monitoring system of any of claims 1 to 19, wherein the primary vessel is a yacht and the secondary vessel is a tender.

21. A vessel monitoring system for locating on a primary vessel, the vessel monitoring system configured to: receive position information associated with a secondary vessel from an AIS message transmitted by the secondary vessel to the primary vessel; receive position information associated with the primary vessel; determine a distance between the primary vessel and the secondary vessel based on the position information associated with the primary vessel and the position information associated with the secondary vessel; and output an alarm condition based on the determined distance.

22. The vessel monitoring system of claim 21, further configured to: compare the determined distance to a predetermined threshold distance; and output the alarm condition in response to determining that the distance exceeds the predetermined threshold distance, wherein the alarm condition provides an indication that the second vessel is adrift from the first vessel.

23. The vessel monitoring system of claim 21 or 22, further configured to: compare the determined distance to a predetermined threshold distance; and output the alarm condition in response to determining that the distance is less than the predetermined threshold distance, wherein the alarm condition provides an indication of a system failure aboard the secondary vessel.

24. The vessel monitoring system of claim 21, 22 or 23, wherein outputting an alarm condition comprises outputting a signal causing at least one of a visible and an audio alarm to be output.

25. The vessel monitoring system of any of claims 21 to 24, wherein the position information associated with the primary vessel is received from a GPS receiver.

26. The vessel monitoring system of any of claims 21 to 25, wherein the vessel monitoring system is further configured to: receive an identification token in the AIS message, the identification token identifying the secondary vessel; compare the identification token to one or more previously stored identification tokens; and only output the alarm condition if the received identification token corresponds to one or more of the previously stored identification tokens.

27. The vessel monitoring system of claim 26, wherein the received identification token is an MMSI number.

28. The vessel monitoring system of claim 26, wherein the received identification token uniquely identifies the secondary vessel.

29. A system comprising a vessel monitoring system according to any one of claims 1 to 20 and a vessel monitoring system according to any one of claims 21 to 28.

30. A monitoring system for locating on a first vehicle, the monitoring system comprising a processing arrangement configured to: receive numerical data; determine a text string based on the numerical data; generate an NMEA sentence comprising the text string; and output the generated NMEA sentence.

31. A monitoring system according to claim 30, wherein the numerical data comprises data received from one or more sensors.

32. A monitoring system according to claim 30 or 31, wherein the numerical data is associated with a second vehicle.

33. A monitoring system according to claim 30, 31 or 32, wherein the monitoring system is configured to determine the text string based on the numerical data by using a lookup table, wherein the lookup table comprises a plurality of predetermined text strings each having associated predetermined numerical data.

34. A monitoring system according to any of claims 30 to 33, wherein the numerical data is not derived from an AIS message.

35. A monitoring system according to any of claims 30 to 34, wherein the NMEA sentence is an NMEA 0183 sentence.

36. A monitoring system according to any of claims 30 to 34, wherein the NMEA sentence is an NMEA 2000 sentence.

37. A monitoring system according to any of claims 30 to 36, wherein the NMEA sentence is an NMEA ATVDM sentence comprising the text string.

38. A monitoring system according to claim 37, wherein the NMEA AIVDM sentence corresponds to an AIS Type 12 message or an AIS Type 14 message.

39. A monitoring system according to any of claims 30 to 38, wherein the monitoring system is further configured to output the generated NMEA sentence to another apparatus.

40. A monitoring system according to claim 39, wherein the other apparatus is a chartplotter.

41. A monitoring system according to any of claims 30 to 40, wherein the first vehicle is a marine vessel.