6.1 The Position Report
6.2 Vessel Speed and Course
6.3 Frequency of Position Reports
6.4 International Data Exchange Formats and Protocols
6.5 Catch and Effort Data Formats
6.6 Other Data Transmission
6.7 Beginning and End of Operation Messages
6.8 Two-way Messaging Capability
The basic requirements for VMS are quite simple: a vessel must be capable of reporting automatically, accurately and reliably its position to the relevant management authority. In addition to this, there exist a number of ancillary functions which the management authority can designate as requirements or options, as well as a range of performances measured in accuracy, speed of data delivery and system integrity and security.
For the purposes of this paper we will refer to the shipboard equipment used in VMS as a VLD, or Vessel Location Device. A VLD must be capable of providing positions of the vessel on which it is mounted with a specified level of accuracy, regularity and speed, to be an effective fisheries management tool. The most common accuracy requirement is for a tolerance of ±100 meters. This level has been established, almost de facto, because this is designated accuracy of uncorrected GPS. The European Commission has set its requirement at a more modest ±500 meters, as has the U.S. National Marine Fisheries Service in its pilot project for the New England groundfish and scallop fishery.
In both cases, this requirement has been relaxed to accommodate the use of Boatracs terminals, as that system’s independent positioning system corresponds to this level of accuracy. There is some consensus amongst fisheries managers that the more relaxed level fulfils most VMS requirements.
Furthermore, accuracy is not the only issue. Using GPS the position of a vessel is calculated on board the vessel for transmission to the management authority. This availability of the calculated position aboard the vessel raises a security issue, i.e. the possibility of tampering with that position before it is transmitted (discussed in detail in section 9).
When, on the other hand, the vessel’s position is calculated at the system’s communications hub, this particular tampering problem is obviated. Almost all of the future planned satellite systems, based almost without exception on GMS mobile telephone protocols, will have an independent means of calculating the position of a mobile terminal.
Though these positions will be less accurate than GPS, sometimes significantly so, they may be sufficient for fisheries management. In addition to that they open the way forward to a situation where a GPS position is transmitted by the vessel and the communications system’s positioning capability is used as an integrity check on the GPS position.
A distinct benefit of the use of GPS for positioning is that the receiver, in addition to its position in latitude and longitude, provides its speed and course. The advantage of this data is twofold: while accurate speed information cannot reliably determine whether or not a vessel is fishing, it can, in conjunction with basic information such as the type of vessel that is being monitored and the kind of fishing gear that it is using, give a dependable indication that the vessel is NOT fishing. Reception, for example, of a report from a purse seiner indicating that it is steaming at 12 knots would eliminate the possibility that the vessel was fishing at the time that the report was transmitted.
Course data can be an effective tool in determining the probability of a vessel engaging in illegal fishing, e.g. when it is observed steaming toward a restricted area, and in intercepting a vessel by either patrol vessels or patrol aircraft.
By using an external positioning system, such as those discussed in section 5.1, the availability of independently calculated course and speed is made impossible. The sole alternative is to use two positions to calculate these values by dead reckoning. The accuracy of this operation is a direct function of the interval between the two position reports (the shorter the interval the higher the accuracy) and the accuracy of those reports.
The requirement for frequency of position reports is normally related to the intensity of a given fisheries management regime and the resources available to respond to VMS observations. In general, existing VMS systems require that vessels report their positions up to hourly, i.e. 24 positions per day. In certain situations, normally when a vessel’s activity appears to be illegal, authorities call for the ability to receive positions at 15 minute intervals.
As virtually all communications systems offer the ability of this frequency of positions, the only remaining issue is the ability of the fisheries management authority to remotely reprogram the VLD so as to vary the frequency of the position. It is expected that any mobile satellite system which offers dynamic reprogramming will meet a fisheries management scheme’s requirement for frequency of reporting. On the other hand, meeting such criteria will often pose difficulties for remote data gathering systems.
Exchanging VMS data between national monitoring agencies is foreshadowed in international agreements and is currently being considered within the European Union. A universal standard format has not been agreed for this purpose and neither has a standard communications system or communications protocol for delivering the data. Agreed standards, such as these, would enable monitoring station software providers to develop software which would provide the ability to exchange position data more easily between agencies. The alternative is that each national system would decide its own format and protocol and every other agency exchanging data with that agency would have to support that format and protocol. This could be very expensive and chaotic to administer. Urgent action is required in an international context to prevent this event.
Transmitting catch and effort data via VMS is not yet well developed. Japan has made some progress in this area with a reporting system which sends a custom format message over Inmarsat A using the X modem protocol. There have also been trials of catch data reporting using Inmarsat C and Argos in other countries. It is urgent that some attempt is made to standardise both the format and the communications protocol for delivery because of the potential use of VMS for transmission of this data by vessels that move between jurisdictions. If this is not addressed, the support of multiple message formats will lead to expensive software on board vessels and create confusion for vessel operators.
It may not be possible to meet the requirements of all monitoring and scientific agencies with a single message format. However, a basic message structure with some flexibility for supporting different species and fishing methods should at least be sought.
The issue of delivery protocol must also be fully standardised. Simplicity and commonality will lead to less expensive systems development and systems which can be applied in a wider range of countries and monitoring organisations. Similar protocols to those used for the delivery of position reports should be considered.
Other information may be derived from sensors linked to the VMS equipment. For example, water temperature or information about the operation of various equipment on board the vessel which might provide an indication of environmental conditions or fishing activity. Much of this information will have a specific purpose and it may be difficult to achieve any standardization. However, some consideration should be given to intention messages to ensure that confusion among vessel operators is minimized and ease of use maximized. The issue of sensor data should also be considered in the longer term as use of this technology develops.
It must be assumed that there will be times when a vessel’s VLD is legitimately out of operation: when it is in port for prolonged periods or being serviced or refitted, for example. Should a vessel simply stop transmitting its position, this will create an anomaly within the VMS where a position is still expected at regular intervals.
The solution to this potential problem is to program the VLD so that it sends to the fisheries manager a special class of message when the system is turned on or off. The action of turning on the VLD simply formats an “entry into service” message which includes, in addition to the vessel identity, its time and position. Likewise, turning off the VLD formats an “end of service” message with the same variables.
There are two variants on these messages. In the case where the power is suddenly cut and the VLD is unable to send its end of service message, when power is restored, it sends an “interrupted service message” which includes Vessel identity, time, position when power cut occurred and actual position.
The other is that, assuming the VLD has an auxiliary battery power supply (see discussion in section 9.2.1) the switch from principal power supply to battery provokes the transmission of an “emergency operation” message which includes the time and current position
Most fisheries managers favour systems which provide two-way messaging capability so that they can not only receive their necessary position reports, but have the capability to address operational messages to individual or groups of vessels (changes in regulations, weather reports, safety messages, etc). The addition of a manual input device aboard the vessel (keyboard, hand-held terminal, PC) adds the catch reporting capability to which most fisheries managers aspire.
Table 6.1 VMS performance requirements
|
Requirement |
Measure |
Tolerance |
|
Position report |
accuracy in meters |
±100m to ±500m |
|
Speed and course |
real or extrapolated |
real reference is preferable |
|
Report frequency |
minimum interval |
15 minutes |
|
Position delivery speed |
interval between calculation and delivery |
availability of near real time if required |
|
Exception messages |
availability of entry to, exit from and interruption of
service or power supply |
availability of near real time for system
integrity |
