AIS Data Accuracy

The Coast Guard has noticed that many AIS users are not updating their unit to accurately reflect voyage related information—navigation status, static draft, destination, ETA, etc. Further, the Coast Guard has encountered AIS units that either do not transmit at all or improperly transmit the vessel’s dynamic data—position, course, speed, heading, etc. The former problem requires due diligence on behalf of the user, the latter is most likely due to the improper installation or operation of external sensors—gyro or heading device and vessel GPS system—inputted into the AIS. AIS users are compelled to properly operate their AIS at all times (33 CFR § 164.46). They should pay close attention to these matters, and are encouraged to make each other aware of AIS discrepancies they come upon. Improper operation of AIS could subject a person to civil penalties not to exceed $25,000 (46 USC §70119) .

Note, AIS data can be invaluable, however, as with any source of navigation information; it should not be solely relied upon in making navigational and collision-avoidance decisions. Further, while AIS allows for safety related ship-to-ship text messaging to communicate with others and make passing arrangements, these communications do not meet the requirements of the Vessel Bridge-to-Bridge Radiotelephone Act (33 U.S.C. 1201 et. seq.) for broadcasts on the designated bridge-to-bridge channel, nor do they relieve a vessel operator from the Navigation Rules requirement to sound whistle signals or display signals.

USCG to Broadcast AIS data

This is the first phase of a Coast Guard Research & Development Center project to develop, design and evaluate the most efficient means by which mariners can receive critical real-time navigation safety information through the use of AIS and its binary messaging capability. The first phase of the project will directly access Physical Oceanographic Real Time System (PORTS) quality checked data from National Oceanographic and Atmospheric Agency (NOAA) servers, and, repackage it for AIS transmission. These broadcasts will commence at 1100 on 11 September 2008 and every 6th minute thereafter, i.e. 11:06:00 a.m., 11:12:00 a.m., etc.

Sometime mid-2009, testing will expand to include the broadcasts of other critical navigation safety information, such as waterway closures, wreck markings, high wind and/or low visibility warnings, etc. We are highly optimistic that—in a not to distant future—AIS binary messaging will extend beyond CVTS Tampa Bay, to all other USCG VTS and ultimately to most waterways within our Nation-wide AIS (NAIS) network. For further information contact Irene Gonin, USCG R&D Center, 1082 Shennecossett Road, Groton, CT 06340 or Irene.M.Gonin@uscg.mil.

New AIS Devices May Not Be Discernable With Older AIS Software (USCG Safety Alert 10-08)

AIS Class B devices are now available in the U.S. These lower cost AIS de-vices are interoperable with existing AIS Class A devices; unfortunately not all AIS Class A units have been updated to readily 'see' these newest AIS devices.

The new AIS Class B devices broadcast and receive virtually the same vessel iden-tification and other information as Class A devices, and they have the same ability to acquire and display targets not visible to radar (around the bend, in sea clutter, or during foul weather). They differ slightly in their features and nature of design, which fortunately reduces their cost (on average $1,000 versus $4,000 for a Class A unit) but, to some extent, affects their performance. They report at a fixed rate (30 seconds) vice the Class A's variable rate (between 2-10 seconds dependent on speed and course change). They consume less power, thus broadcast at lower strength (2 watts versus 12 watts of Class A), which impacts their broadcast range. Despite these differing design parameters, and after extensive testing by the Coast Guard Research and Development Center, the Coast Guard deems that AIS Class B devices can operate properly and safely amongst Class A devices and offer simi-lar AIS benefits.

There is a significant shortcoming inherent in this evolving technology. Although all Class A devices will receive Class B information; unfortunately, some older Class A models are unable to render this information on their Minimum Keyboard and Display (MKD) or may only have available the Class B vessel's dynamic data (i.e. position, course and speed) but not its static data (i.e. vessel name, call-sign). Therefore, the Coast Guard cautions new AIS Class B users to not assume that they are being 'seen' by all other AIS users or that all their information is available to all Class A users. Further, we strongly encourage users of certain AIS Class A units to, as soon as practicable, update their MKD's and/or other external navigation display systems (e.g. Electronic Charts Systems, Electronic Chart & Display Infor-mation Systems, radar, etc.) in order to view this new stream of valuable AIS information that will enhance navigation safety and mitigate the risk of collision. For a listing of Coast Guard type-approved AIS Class A units which require a firmware update in order to display AIS Class B information, click here.