A
thin breeze skittered
across the Gulf of
Maine, and a low cloud
ceiling stamped out any moon-
light, making for a dark night
aboard my dad’s J/44, Southern
Cross. My wife and I were
standing watch with nothing
to look at save a few distant
lights. While she enjoys excel-
lent vision, I suf er from severe
red-green color blindness,
which made it hard to deter-
mine whether I was looking at
bow and stern lights, multiple
vessels, or both. Given that in
August of 2006, the Automatic
Identifi cation System (AIS)
as we know it today wasn’t yet
widespread among recreational
craft, we spent the next few
minutes trying to discern the
nature of the scene before con-
sulting the radar, getting on the
VHF and waking our captain.
We eventually determined
that these lights belonged to
two moderate-size commer-
cial fi shing vessels anchored
close together somewhere of
Gloucester, Massachusetts,
and that passing well astern
would be simple. While this
situation illustrates how con-
fusing nighttime navigationcan be, AIS technology has
since removed the (ugly) word
“assumption” from most
crossing situations, while also
providing signifi cantly better
situational awareness. Here’s a
look at what’s changed in the
decade since that confusing
summer night.A Look at the Gear
While AIS technology is capa-
ble of disseminating a wide
range of information, its most
common use is to allow mar-
iners to “see” other nearbytrai c to avoid vessel-to-vessel
collisions. The basic concept is
fairly simple: An onboard AIS
transponder broadcasts a ves-
sel’s speed, course and location
information, derived from the
unit’s internal GPS, along with
the boat’s unique nine-digit
MMSI number, assigned by the
FCC. The information is sent
out over dedicated VHF chan-
nels while the AIS transponder
also listens for other vessels’
incoming signals. Properly
programmed MMSI num-
bers allow a mariner to directlycall another vessel (think of
a cellphone number for your
VHF) rather than rely on easily
missed VHF broadcasts. In
many cases, AIS information
can be overlaid onto an elec-
tronic nautical chart (or radar
display), giving navigators a tre-
mendous level of big- picture
awareness, especially when
paired with radar imagery.
There are two types of AIS
available to mariners: Class A
and Class B (see “AIS Carriage
Requirements,” below).While
some may fi nd the technicalCOURTESY OF THE MANUFACTURERWE SEE YOU
Developed for commercial shipping and collision avoidance, AIS is now an everyman’s tool for watchkeeping
and navigation — and that’s just for starters.BY DAVID SCHMIDTWhile AIS is a huge aid to
safety, the Coast Guard does
not mandate that all mariners
carry this equipment. Here’s
a breakdown of the kinds of
vessels that are required to
carry properly installed USCG-
approved AIS transponders in
U.S. waters.Class A AIS:- Commercial self-propelled
vessels of 65 feet or greater - Commercial towing vessels
of 26 feet or greater and over
600 horsepower - Self-powered vessels that
are USCG-certifi ed to carry
more than 150 passengers, or
that move certain dangerous,
fl ammable or combustible
cargoes in bulk- Commercial motorized
dredging vessels that work in
a way that’s likely to interfere
with the safe navigation of
other commercial vessels
Class B AIS:- Commercial fi shing vessels
and most passenger vessels
that operate outside a USCG
Vessel Tra c Service or Vessel
Movement Reporting Area
may use a lower-cost, fully
compatible AIS Class B unit in
lieu of a Class A device.- While recreational boaters
aren’t legally required to carry
AIS, a recent change (dated
March 2, 2015) to the USCG’s
AIS requirements pertains
to “any vessel equipped
with AIS,” meaning that all
recreational boaters who
elect to carry AIS must abide
by some of the USCG’s new
AIS operations requirements.
See navcen.uscg.gov, “AIS
Frequently Asked Questions,”
for more information.
AIS Carriage RequirementsBOATS & GEARmay 2016cruisingworld.com68