Next was the new
VHF radio with AIS capability (Automatic Identification System). My
radio is mounted on top of the instrument
panel so making this change was very simple and took just a few
Because it was the same brand as my existing radio all the connectors
mated so the electrical hookup was also easy. AIS is a very interesting
and if you are buying a new radio I would certainly consider it -
you cruise in places that have commercial traffic. The extra cost are
reasonably small and the benefit large.
Plus no additional antenna is needed - the normal
VHF antenna serves a
you are not familiar
with AIS it is a radio signal that provides real time tracking system
boats. It is required in most all commercial vessels and many larger
craft are also adding it. It
sends out a
signal containing the boat’s name, location, heading, speed, distance
of it as being very similar to
the system air traffic controllers use to monitor aircraft in a given
true duplex AIS system
provides the ability to both transmit your information and receive the
from others. The range is usually 10 miles or better so a wide area is
But like all things marine it does come at a cost. Typical equipment
runs from $600 to $1000. An alternative is a simplex receive only
downside is others can’t see you but it does offer you the ability to
One of the easiest ways to add the simplex function is to buy a
marine VHF radio with AIS. These can be purchased for less than $250
and as I
am finding it works very well.
the VHF radio there
is a screen that can be selected to display the AIS information. The screen (similar to a
radar screen) is
small but still gives the general idea of the nearby vessels location
relation to your boat. Using a control knob I can rotate through the
AIS transmitting boats within up to 10 miles (range is selectable) and
one. Once done the text information about the boat displays - including
is this important to
me? As you may know I have a good many river miles logged. On a regular
during those trips I find the need to share the river with LARGE
traffic. Often I need to communicate with them to safely pass or
problem is calling them on the radio. There may be two or three tows in
general area so how do I hail the right one? Their name is usually on
transom but often very hard to read at a distance. The name is also
the side but by the time I can read it I am already overtaking so it
help. And approaching from the front offers absolutely no clues at all.
Normally I try to use what ends up being a cryptic combination of their
location and description but it is far from optimal. AIS solves this
But it makes it even
easier. With the
press of a couple
buttons I can make a direct call to the other craft using the radio’s
(Digital Selective Calling). The radio in the other boat sounds an tone
like a “ring”
and they answer allowing two way communication. I don’t have to hail
know their call name (although I do at that point).
it gets even better
if the radio’s NMEA interface is connected the GPS/Chartplotter. Now the AIS vessel is
overlayed on the chartplotter's chart
and selecting it's icon provides the vessels info on the plotter screen. This is particularly
useful when cruising
rivers because a ship maybe located just a half mile away - right
next bend - but not visible from the helm.
Also, on my plotter I can set alerts based on
distance and or time and a
alarm will sound if the vessel crosses them (more below).
After a season of use I will say I have always
spotted the crafts
approaching forward before the alarm sounded BUT several times faster
equipped pleasure craft have been advancing from the rear unnoticed and
alarm made me aware of the situation.
on a narrow section
of the Cumberland River I was warned on a boat coming up aft. I looked at the data and
it showed a 60'
craft running 30 MPH. I thought there was obviously an error of some
type - 60'
and 30 MPH, now way! I
was wrong. I watch
the speed drop as it came off plane
to pass me (which I greatly appreciated) and then bounce back up as he
the throttle. Yes, he was cruising at 30 MPH.
you are curious about
AIS here is a free web site that requires no download to view AIS ships - http://www.marinetraffic.com/ - although the data is a little delayed. There are also several app’s available for both Android and Apple
display the same AIS information as the VHF radio and place the boat
maps or charts like the plotter. In fact, If you have both cell service
data to burn the app could be used in place of the marine hardware. For
my Android tablets and phones I like “FindShip”
which is available for free and provides real time information. I actually use the paid ($3.99) version,
Pro. The main additional feature it offers is the ability to show the
of any ship over the past 30 days. Not real useful but certainly
The paid version also eliminates the ads but honestly they aren’t very
obtrusive on the free app. And you don't have to be near the water for
these to work. I often fire up the app while sitting at home
see what is going on at Kentucky Lake 150 miles away.
conclusion, I must
say I have been very impressed with the capabilities of AIS.
Dollar for dollar I think it is the best
value of all the equipment purchased in the electronics upgrade.
top photo of the small screen on the radio itself with AIS targets
showing. The AIS range on this radio is up to 10 miles and in
this situation is is set to display up to 2NM. The dots
the location of the AIS boats relative to your location. The
small line radiating from the dot points to the boats heading.
The dots change from a circle to a black dot as you rotate
through the list of available targets.
the LIST button brings up the screen above showing either the
name or the MMSI number of the available targets. In
this case Golden H is selected and you can see its black dot location
is about 1 NM to the
starboard and slightly aft and heading away. Selecting the INFO button
brings up another screen with more detailed information of the boats
speed, heading, ect. By selecting the CALL button I can
the quick process to make a direct radio call to Golden H.
the radio networked I can bring up this screen on the plotter. It
list the names or the MMSi numbers of all the AIS vessels in the
area. In this situation there are eight so I have to scroll
through the screen to see them all. Although the radio is maxed
at a 10 mile range the plotter will usually pickup anything with in 15
to 18 miles. On this screen I have selected the Stan Humphreys.
Touching it brings up the screen below.
is the INFO screen showing the AIS info on the Stan Humphreys.
amount of data for the individual boat will vary but this one is fairly complete. This is a loaded
(draught 9.8) river tow making 4.9 MPH on a heading of 301. The
Length and Beam are shown (this is just the tug - not the load of barges). It is 7.75 miles away from me on a
bearing of 264 degrees. The system tells me it's status is
meaning there is no collision course at the present time. The CPA (Closest
Point of Approach) shows if we both stay on our present course the
closest we will come to one another is 6.96 miles in 38 minutes and 34
seconds (TCPA - Time To Closest Point Of Arrivial) I can set alarms for both CPA and TCPA and if it is
calculated the boats will pass nearer than those limits the alarm be
activated. For example, I can say as long as any approaching
vessels are more than a mile away or more than 3 minutes away thats OK
but if it is calculated to pass closer let me know. This is a great safety feature.
the bottom there is a "CALL" button which will start the direct radio
call and the "SHOW" button which brings up the screen below.
is how the icon of a vessel shows on the chart screen. It
it right on the chart so I have a very good idea of it's location.
The line again shows its direction of travel. If it
in the water only the triangle will show - no line.
I am just cruising and notice the triangle symbol on the chart, all I
have to do is touch the triangle. A text box will appear showing
the boats name
or MMSI #. Touching the text box then brings up the INFO
screen shown several photos above. It is just a quicker way to get to
the boat's AIS data.
- Class A AIS transmits the craft's MMSI number and other critical
location information every 2 to 10 seconds BUT the other data like the
vessel's name, draught and size are only broadcast every 6 minutes.
So you may have to wait a little to get all the
info. (see full list below)
of data transmitted by AIS
An AIS transceiver sends the following data every 2 to 10 seconds
depending on a vessel's speed while underway, and every 3 minutes while a
vessel is at anchor:
- The vessel's Maritime Mobile Service Identity (MMSI) – a unique nine digit identification number.
- Navigation status – "at anchor", "under way using engine(s)", "not under command", etc.
- Rate of turn – right or left, from 0 to 720 degrees per minute
- Speed over ground – 0.1-knot (0.19 km/h) resolution from 0 to 102 knots (189 km/h)
- Positional accuracy:
- Longitude – to 0.0001 minutes
- Latitude – to 0.0001 minutes
- Course over ground – relative to true north to 0.1°
- True heading – 0 to 359 degrees (for example from a gyro compass)
- True bearing at own position. 0 to 359 degrees
- UTC Seconds – The seconds field of the UTC time when these data were generated. A complete timestamp is not present.
In addition, the following data are broadcast every 6 minutes:
- IMO ship identification number – a seven digit number that remains unchanged upon transfer of the ship's registration to another country
- Radio call sign – international radio call sign, up to seven characters, assigned to the vessel by its country of registry
- Name – 20 characters to represent the name of the vessel
- Type of ship/cargo
- Dimensions of ship – to nearest meter
- Location of positioning system's (e.g., GPS) antenna on board the vessel - in meters aft of bow and meters port or starboard
- Type of positioning system – such as GPS, DGPS or LORAN-C.
- Draught of ship – 0.1 meter to 25.5 meters
- Destination – max. 20 characters
- ETA (estimated time of arrival) at destination – UTC month/date hour:minute
- optional : high precision time request, a vessel can request other vessels provide a high precision UTC time and datestamp