Have questions about AIS? We have answers!
This FAQ page will hopefully answer your questions. If it does not, send us
your questions to:
info@milltechmarine.com.
Index of Questions ...
- What is AIS?
- How
can I use the data stream from an AIS receiver?
-
Is it possible to connect my AIS receiver to a chart plotter?
-
Do these AIS receivers work with Raymarine's E Series
and C Series chart plotters?
-
Will an AIS receiver work with my network solution onboard?
- What
electronic chart programs can handle AIS today?
- Can I use AIS solutions with Microsoft's new Vista
operating system?
- What are
the basic steps to install an AIS receiver?
-
I don’t have a spare serial port on my computer. How do I hook up the AIS
receiver to my computer?
- What
type of VHF antenna do I need for my SR161/SR162?
- Can I use an
existing marine VHF antenna?
-
Speaking of distances, does the AIS receiver “see” ships that are far away?
-
I am interested in buying an AIS receiver but I do not own a compatible PC
software package yet. How can I get started?
- What type of
ships show up on an AIS display?
-
I have hooked up my AIS receiver. Why don’t I see ships immediately?
-
The ships show up as numbers? I thought I would also see the name of the
ship.
-
So what kind of information is broadcast for each ship and how often is it
updated?
- Which
VHF channels or frequencies are used with AIS?
-
Milltech Marine sells a dual channel scanning receiver (SR161) and full time dual channel receivers (SR162/SR162G).
What are the differences between the models?
-
If I am only receiving AIS information from one channel at a time, does this
mean the SR161 will not pick up the transponder broadcasts from half the
ships in my area?
-
How does the SR161 dual channel scanning receiver compare to a single channel receiver such as the Nasa AIS Engine?
-
Can I get more information on how the dual channel system works?
-
Where can I find out more specific information about AIS?
- Do you ship products outside the USA and how do I
get information on shipping options and costs?
AIS or the Universal Shipborne Automatic Identification System (AIS) is a
ship transponder system that is currently used by most of the commercial
shipping industry. AIS uses two marine VHF channels. Each ship equipped with an
AIS transponder sends out a packet every few seconds with information about the
ship and its voyage. With an AIS receiver, you can pick up these radio signals
and have them translated into a NMEA data sentence that can be accessed using a
standard RS232 serial interface.
Many modern computer-based marine navigation software packages, such as Rose
Point Coastal Explorer 1.1 and Nobeltec Visual Navigation Suite 9.0, can be
configured to interpret the incoming AIS data stream and convert the information
into human readable information. These packages also support plotting nearby
ships on digital charts and can show your position (via a separate GPS) in
relation to the other vessels in the area that have AIS transponders.
Today most modern chart plotters support being connected to an
AIS receiver and are able to display AIS targets. Some of the manufacturers that
support this today include Raymarine E and C Series, Garmin, Standard Horizon,
Furuno, Seiwa and Interphase. Other manufacturers are working on this feature
and have stated they will be able to support AIS in future models. For further
information contact your supplier and ask about AIS support in their product.
For more information on how to use a Smart Radio AIS
Receiver with an AIS-capable chart plotter, see our special chart
plotter information page.
Yes, the Smart Radio AIS receivers work well with Raymarine E series and C series
chart plotters with the latest
ROM upgrade from Raymarine. Normally, you would connect the AIS Receiver to the
high speed NMEA input on the chart plotter. For more
information on how to use a Smart Radio AIS Receiver with Raymarine AIS-capable
chart plotters, see our special chart
plotter information page, our product documentation and our online
troubleshooter.
All networks that can handle NMEA VDM serial data at the speed 38400 baud
will be able to handle AIS data. We have been informed that Silva and Navnet are
able to do so. Raymarine’s Seatalk will most likely not be able to handle AIS
data. Ask your network provider for further information.
Today several software packages support AIS. The ones known to work are:
- Rose Point Coastal Explorer 1.1
- Maptech Chart Navigator Pro
- Nobeltec Visual Navigation Suite 8.0 or above
- Nobeltec Admiral
- Capn 8.0
- Boatcruiser 2.0
- Fugawi Marine ENC
- Memory Map Navigator Pro
- Global Navigation Software NavPak
- ICAN Regulus
- Xanatos Titan
- EuroNav seaPro
- Y-tronic Yacht-AIS
- Seaclear
- DigiBOAT Software-On-Board
- Navicon AIS Navigator
- COAA Ship Plotter
- MaxSea with the Mobiles Module
For the Mac, the recommended packages include:
Software that can handle the NMEA VDM messages and display the data should
work with the SR161/SR162 AIS Receivers. Ask your provider for further
information.
Yes, it is possible to use AIS solutions with Windows Vista. The Coastal
Explorer product we sell is certified to work with Vista. In addition, if you
need to connect the Keyspan USB Serial Adapter, You can download a driver
here.
The receiver has three connections.
- One connection is for a standard marine VHF antenna. The Smart Radio AIS
receivers use a BNC connector for the VHF antenna connection. If you need to connect to typical VHF radio
antenna cable that uses a PL-259 / SO-239 connector, you’ll need an SO-239
to BNC adaptor.
These are available from Milltech Marine's online store.
- The second connection is a 9 pin serial port which can be connected to a
computer serial port using a standard serial cable (all AIS receivers from
Milltech Marine include a serial cable).
- The third connection is for 12 volt DC power.
Once these connections have been made, simply configure your marine
navigation software to utilize the new serial port connection as an incoming
“listener” serial data stream. Note that the Smart Radio AIS receivers use 38400
baud by default so make sure you configure your software program appropriately.
For the SR162G, you will need to also
connect the included GPS antenna and make sure it is placed in a location that
has a clear path to the sky.
You typically have two options.
The first option is to use a USB to serial adaptor. Connect the serial end to
the AIS receiver and the USB end to a spare USB port on your computer. Make sure
you know which COM port has been assigned to the USB serial port and configure
your software appropriately. Note that some cheaper serial to USB adaptors can
be unreliable or cause system crashes. Test the adaptor thoroughly before
deploying it on your boat. Milltech Marine has tested the
Keyspan
High Speed USB Serial Adapter recommends this solution. It can be ordered
from our online store. This unit supports both the
PC and the Mac.
The other option you have with the Smart Radio AIS receivers, is to use the
unit as a NMEA data stream consolidator. What does this mean? You can direct the
GPS NMEA data stream into the input pin on the AIS receiver serial port and the
unit will then combine the GPS sentences with the AIS sentences and output on
the output pin of the serial port a combined data stream. You would then only
need one serial port on your computer and this port would have both GPS and AIS
data coming through it. Full details are in the installation manual that comes
with the Smart Radio AIS receiver. You can also purchase this cable separately
from Milltech Marine.
The VHF antenna should fulfill at least the following requirements:
- Antenna type: Vertical radiator
- Antenna gain: 0 – 3 dBd
- Impedance: 50 ohm
Yes, you can use a splitter to share your existing VHF antenna to your
VHF/DSC radio and your AIS receiver. It is highly recommended that you use an
active splitter that automatically disconnects the signal to the AIS receiver if
a transmission is detected from the VHF radio. Milltech Marine sells an active
VHF Antenna Splitter. More information on this
device can be found by clicking here. If you use a common T-splitter
and then
broadcast on the VHF radio, it is possible that you could damage the AIS
receiver. Since you have two receiving devices on one antenna, you may also
experience some signal degradation. While broadcasting on the VHF radio, you will likely see some interruption of incoming
AIS signals. Since AIS broadcasts from each ship are repeated every few seconds,
this is not normally noticeable in your tracking software.
For best performance,
use a dedicated VHF antenna that is mounted away from your VHF radio antenna.
This will mean less interference and will allow both the AIS receiver and the
VHF radio receiver to get maximum receiving distances. Milltech Marine sells an
excellent VHF antenna specially designed for use with AIS receivers. See our
products page for more information.
Another option is to attach a portable VHF antenna to the AIS receiver.
Milltech Marine sells a VHF antenna that works well for this purpose. Note:
since this antenna is fairly small, reception will not be as good as a full size
VHF antenna. For more information and to order this antenna,
click
here.
Since AIS uses the same VHF frequencies as marine VHF, it has similar radio
reception capabilities – which is basically “line of sight”. This means that the
higher your VHF antenna is mounted, the greater the reception area will be.
Reception from ships that are 20 miles away on open water is not uncommon. Note
that AIS has a major advantage over radar since it can “see” ships within radio
reception range that are behind large objects, such as other ships or points of
land.
Again, you have at least a couple of options. If you want a “free” solution,
Milltech Marine bundles an AIS resource CD with every AIS receiver. The CD
includes the Seaclear marine navigation package, which supports displaying your
position on digital charts, route planning and display of AIS information. The
CD also includes digital planning charts for all of the US coastal areas.
If you are just getting started with computer based marine navigation, then
consider one of the software bundles that is offered by Milltech Marine. We
feature the Rose Point Coastal Explorer 1.1 product, bundled with either the
Smart Radio SR161 or SR162 at very competitive prices. These products work great
together.
If you are a current Nobeltec Visual Navigation Suite user, consider
upgrading to version 8.0 which now supports AIS. The latest version of Memory
Map Navigator Pro also supports AIS on both the PC and the Pocket PC.
Just about every commercial vessel will have an AIS transponder.
Specifically, AIS is mandatory on all ships of 300 gross tonnage and upwards
engaged on international voyages, cargo ships of 500 gross tonnage and upwards
not engaged on international voyages and passenger ships irrespective of size.
See the
US Coast Guard web page on AIS for more information. Other smaller
commercial ships, such as fishing vessels, will equip themselves with AIS
transponders voluntarily since there are major safety benefits to using AIS.
It normally takes a few seconds for ships to appear since the receiver needs
to pick up a transmission from the remote ships’ transponders. The system allows
for ships to rebroadcast their information every few seconds so within a minute
you will typically see nearby ships appear on your navigation package.
Just wait. Ships broadcast voyage information every few seconds but also
broadcast full ship information every 6 minutes. So after a few minutes, you
should see complete information for every ship that the AIS receiver has picked
up.
A Class A AIS transponder broadcasts the following information every 2 to 10
seconds while underway, and every 3 minutes while at anchor:
- MMSI number - unique referenceable identification
- Navigation status - “at anchor”, “under way using engine” or “not under
command”
- Rate of turn - right or left, 0 to 720 degrees per minute
- Speed over ground - 1/10 knot resolution from 0 to 102 knots.
- Position accuracy - differential GPS or other and an indication if RAIM
processing is being used
- Longitude - to 1/10000 minute and Latitude - to 1/10000 minute
- Course over ground - relative to true north to 1/10th degree
- True Heading - 0 to 359 degrees derived from gyro input
- Time stamp - The universal time to nearest second that this information
was generated
In addition, the Class A AIS unit broadcasts the following information every
6 minutes:
- MMSI number - same unique identification used above, links the data
above to described vessel
- IMO number - unique referenceable identification (related to ship’s
construction)
- Radio call sign - international call sign assigned to vessel, often used
on voice radio
- Name - name of ship, 20 characters are provided
- Type of ship/cargo - there is a table of possibilities that are
available
- Dimensions of ship - to nearest meter
- Location on ship where reference point for position reports is located
- Type of position fixing device - various options from differential GPS
to undefined
- Draught of ship - 1/10 meter to 25.5 meters (note “air-draught” is not
provided)
- Destination - 20 characters are provided
- Estimated time of Arrival at destination - month, day, hour, and minute
in UTC
AIS transponders and receivers use two VHF radio frequencies: 161.975 MHz
(AIS1, or channel 87B) and 162.025 MHz (AIS2, or channel 88B). The USCG has
asked the Federal Communications Commission to authorize any US vessel to
operate AIS on these two channels under its existing ship station license. The
FCC released a
Notice authorizing operation of AIS under a ship’s existing station
license.
All the units can receive AIS information from either AIS channel. The SR161 can
only receive information on one channel at a time but will automatically switch
to the alternate channel if it detects interference on the current channel.
The SR162/SR162G can receive all AIS
broadcast information from both AIS channels simultaneously and consolidate the
information from both channels into a single data stream. It is a true dual
radio receiver. This generally means you will acquire new vessels sooner with
the SR162 and you will also get the full information about a vessel in a shorter
period of time.
The SR162G also includes an integrated 12 channel GPS module as well as a detachable GPS
antenna with a 16 foot cable. With this model you can receive AIS traffic information and GPS
position information as a single consolidated data stream over the RS232 serial
port.
No – the AIS system uses two channels for redundancy. Ships broadcast
information alternating between the two channels. Therefore, you will eventually
pick up information on for every ship, even if the AIS receiver can receive on
one channel.
Both units are single channel AIS receivers, however the SR161 has the
advantage that it can scan between the two AIS channels and will automatically
use the channel with the best radio reception. Other brands of single channel
AIS receivers typically must be set to use one channel or the other and do not
scan for the best signal. The SR161 from Milltech Marine is also significantly
cheaper than other single channel AIS receivers.
The best source for more information is to look at the documents related to
the AIS standard. On the subject of dual channel support, the standard states:
“The normal default mode of operation should be a two-channel
operating mode, where the AIS simultaneously receives on both channels in
parallel. In order to accomplish this performance, the AIS transponder should
contain two TDMA receivers.
Channel access is performed independently on each of the
two parallel channels.
For periodic repeated messages, including the initial link access, the
transmissions should alternate between AIS 1 and AIS 2. This alternating
behaviour is on a transmission by transmission basis, without respect to time
frames.
Transmissions following slot allocation announcements, responses to
interrogations, responses to requests, and acknowledgements should be
transmitted on the same channel as the initial message.
For addressed messages, transmissions should utilize the channel in which
messages from the addressed station were last received.
For non-periodic messages other than those referenced above, the transmissions
of each message, regardless of message type, should alternate between AIS 1 and
AIS 2.
Base stations could alternate their transmissions between AIS 1 and AIS 2 for
the following reasons:
– To increase link capacity.
– To balance channel loading between AIS 1 and AIS 2.
– To mitigate the harmful effects of RF interference.”
Also the US Coast Guard site has the following information:
“Although only one radio channel is necessary, each
station transmits and receives over two radio channels to avoid interference
problems, and to allow channels to be shifted without communications loss from
other ships.”
See the US Coast Guard site on AIS:
http://www.navcen.uscg.gov/marcomms/ais.htm
The full text for the AIS standard: “RECOMMENDATION
ITU-R M.1371-1 -
Technical characteristics for a universal shipborne automatic
identification system using time division multiple access in the
VHF maritime mobile band” can be purchased online from:
http://www.itu.int/rec/recommendation.asp?type=items&lang=E&parent=R-REC-M.1371-1-200108-I
Yes, we are happy to ship products to most countries around the world. For
information on shipping options and prices for shipping, use the online shopping
cart in out online store. Note
that we do not recommend US Postal Service delivery services for international
orders as these shipments are not tracked and typically take longer than
expected.
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