Home | Contact ST  

Soapbox

2013:  JAN | FEB | MARCH | APRIL | MAY | JUNE | JULY | AUG | SEPT | OCT | NOV | DEC
2012:  JAN | FEB | MARCH | APRIL | MAY | JUNE | JULY | AUG | SEPT | OCT | NOV | DEC


March 2012 Issue

AIS Application-Specific Messages: Expectation and Reality
By Lee Alexander

The automatic identification system (AIS) contributes to safety of navigation and marine protection by enhancing situational awareness of vessel movements and providing navigation-related information in the form of AIS application-specific messages (ASMs). These include meteorological and hydrographic data (met/hydro), dangerous cargos, safety and security zones, recommended routes, status of aids to navigation and other time-sensitive safety information. This information can be broadcast from any AIS shore station and received by shipborne AIS equipment that is installed onboard most oceangoing vessels as required by national regulations.

It is expected that AIS ASMs will become an important component of the e-navigation concept of operation. Particularly, AIS ASMs are one way to achieve key elements of e-navigation, which the International Maritime Organization (IMO) defines as the “harmonized collection, integration, exchange, presentation and analysis of maritime information onboard and ashore by electronic means.”

Three major groups play a role in the implementation and use of AIS ASMs: standards developers, service providers and maritime users. While the International Telecommunication Union specified the technical characteristics and structure of AIS ASMs (ITU-R M. 1371), it is the IMO that defined the content parameters (IMO SN.1/Circ. 289). The International Association of Lighthouse Authorities recommended some further refinements and clarifications.

At present there are no prescribed display standards for AIS ASMs for shipborne or shoreside equipment, such as radar, electronic chart display and information systems (ECDIS) and integrated navigation systems (INS). The IMO, however, has issued guidance for the presentation and display of ASMs (SN.1/Circ.290), which was purposely left general since it was considered premature to propose specific presentation or display standards until further experience is gained. These guiding principles outline the use of consistent symbology across all displays and other attributes including, uniqueness (one possible meaning), nonambiguity (distinct; able to determine differences) and being intuitively obvious (an easily recognized symbol, icon or pattern). The IMO’s guidance also suggests having a basic symbol for different categories and that further attributes should be enhancements—not changes—to the basic symbol.

In concept, few would likely disagree with these principles. However, in practice it may be difficult to achieve a consensus between providers and users as to what is really suitable or effective. Even with clearly defined data contents, what constitutes a suitable display is subjective and influenced by opinion or user preference. As such, test trials are needed before developing specific recommendations. This includes practical experience on the four basic means of displaying AIS ASMs: alphanumeric; graph; point, line or polygon; and symbol or icon.

Further testing is also needed on how AIS ASMs should be displayed in conjunction with chart-related information. For both ECDIS and INS, it is the current navigation situation (e.g., open ocean, coastal or approach) and the task-at-hand (e.g., grounding or collision avoidance, situational awareness, etc.) that influence what is needed, when and in how much detail. Ideally, AIS ASMs and the International Hydrographic Organization’s new Universal Hydrographic Data Model (IHO S-100) will be compatible in terms of similar data content and parameters such that both types of data can be used in ECDIS and INS. This will be crucial when dealing with dynamic met/hydro information.

The challenges associated with providing AIS ASMs are more organizational than technical. Based on experience, it may be difficult and time-consuming to establish the infrastructure for one government agency to convert met/hydro sensor data into a binary format and then pass it to another agency to be broadcast via AIS base stations as an AIS ASM. Oftentimes, different agencies have different ideas on what types of met/hydro data are important, and the level of detail or precision that is required. While most see the need to provide met/hydro data, agreeing on the specific details regarding data parameters, formatting and distribution can be problematic. Implementing an AIS ASM “service” will require cooperation among government agencies, equipment manufactures and maritime user groups. Specifically, there is the “acceptance dilemma,” whereby government agencies are hesitant to commit resources to establish a service without a commitment by industry and user groups to actually use it. Conversely, the industry is reluctant to use the service until it is either operational or required.

For maritime user groups, there is the challenge of managing expectations. In particular, there may be a disconnect between expectations and reality. The expectation is if time-critical navigation safety information is needed for decision-making, then it will be provided reliably in a data format compatible with existing shipborne equipment. This may be similar to what occurred in the mid-1990s with GPS. To become fully operational required a transition from intermediate operational capability to full operational capability. There was also a need for a differential GPS broadcast service that eventually included receiver autonomous integrity monitoring.

Don’t get me wrong—I am an optimist rather than a pessimist. The challenges associated with implementing AIS ASMs can be overcome. But to do so, there has to be a commitment by all stakeholders and the necessary resources to turn expectation into reality.


Dr. Lee Alexander is a research associate professor at the Center for Coastal and Ocean Mapping at the University of New Hampshire. Previously a research scientist with the U.S. Coast Guard and a visiting scientist with the Canadian Hydrographic Service, he serves on committees and working groups concerning AIS and e-navigation. He has published reports on navigation technologies and co-authored a textbook on electronic charts.


2013:  JAN | FEB | MARCH | APRIL | MAY | JUNE | JULY | AUG | SEPT | OCT | NOV | DEC
2012:  JAN | FEB | MARCH | APRIL | MAY | JUNE | JULY | AUG | SEPT | OCT | NOV | DEC

-back to top-

Sea Technology is read worldwide in more than 110 countries by management, engineers, scientists and technical personnel working in industry, government and educational research institutions. Readers are involved with oceanographic research, fisheries management, offshore oil and gas exploration and production, undersea defense including antisubmarine warfare, ocean mining and commercial diving.