Change to St. Lawrence Seaway water level AIS message

By Brian at October 13, 2010 17:15
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Below is the text of a recent St. Lawrence Seaway notice regarding a change to their version of an AIS message used to transmit water level information:

AIS Water Level Data Transmission
In support of vessels using a draft optimization tool, mariners are advised that effective October 5, 2010, the water level data being transmitted via AIS will be based on actual readings, as currently done, or based on readings of adjacent sensors, in the event of problems with the primary sensor. The AIS water level message type will display ‘act0’ when the level is from the primary sensor and ‘est1’ when the level is estimated using data from adjacent sensors. The AIS version message has been changed to 4.1 from 4.0 to reflect this modification.
October 5, 2010

The pdf version of the notice is available here.

Here is version 4.0 of the water level message:

It's unclear to me where the "act0" and "est1" indications have been placed, but probably in the "reserved for future use" bits in the Reference Datum or Reserved fields.  The Notice states that "The AIS water level message type will display ‘act0’ when the level is from the primary sensor and ‘est1’ when the level is estimated using data from adjacent sensors."  This is somewhat presumptious - the actual portrayal would depend on how the manufacturer of the navigation system implemented it.

Th St. Lawrence Seaway has been on the cutting edge in the use of AIS since the early 2000's for which they should be commended.  However, they mostly serve a captive audience so they can make these sort of changes fairly easily.  The problem is that the rest of the world is using other messages, and it is unlikely many manufacturers will implement the SLS messages in their software, putting users at a disadvantage if they do sail the Seaway.

There is an international effort to develop and use common AIS messages, and to establish a registry of international and regional messages.  IALA is hosting this registry, which (unfortunately) currently has no submissions.  In the US, we are actively working to clarify the process for development and qualification of new mesages, and plan to submit messages to the IALA registry.  Others, including the SLS are encouraged to submit messages to the registry and are invited to join in or find out more about the US efforts on AIS application specific messages.

Rose Point implementing new AIS ASMs?

By Brian at March 24, 2010 16:09
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Over at Mad Mariner, Tim of the Navagear and Puget Sound Maritime blogs posts a review of the new Rose Point Coastal Explorer 2010 navigation software.  An excerpt from his review:

"At the same time, the features that are new remain consistent with Rose Point's goal of making useful information more easily available to boaters. Examples include support for cruising guides such as the Atlantic Cruising Club's Marina Guides, and new weather options such as support for XM WX weather, NEXRAD weather radar data, and upcoming AIS weather and conditions broadcasts."  (emphasis added)

We'll see if we can find out more information about their implementation of what we assume are the new IMO application specific messages, commonly known as AIS binary messages.  We have been encouraging manufacturers to begin implementing the new messages, although they are not finally approved until they get through the next meeting of the Maritime Safety Committee (MSC) at IMO.  The next MSC meeting is scheduled for June 2010.