The AIS module is an optional module of ScanNav. When
lets you visualize on screen all boats equipped with a transmitter
(required above 300 tons), and manage anti-collision alerts. Radar ARPA
or MARPA targets are also managed starting from version 10.1 of ScanNav.
AIS targets are represented on screen in a similar way
to your own
boat, with or without heading line, track, and corridor
proportional to the target's real dimensions. When placing the mouse
over an AIS target, a popup window will show all information such as
the target's name, size, heading, speed, destination,etc... Options
related to the AIS module are grouped in the following 2 locations:
Note: entries of menu "Options -> "AIS/ARPA" are also available
dispatched under menus "File" and "View" for historical reasons, so as
not to disturb habits. They will be removed from these alternate
locations in further releases.
tab in the "Preferences"
(see "Display and alerts" below)
- and menu "Options"
Targets": Lets you globally show/hide the display of AIS
if this option is unchecked, no target will be displayed.
list": To display targets in a list. See appropriate
chapter further in this document.
position reports Import" : See appropriate chapter further
in this document.
In case of collision risks,
an audible alarm is
triggered, and a window opens showing all properties of the target, as
well as alert conditions (approaching speed, minimum estimated distance
(CPA/TCPA), etc...) .
This window can also be opened on demand using the "properties" button
in the AIS list view.
Display and Alert
can tune all display and alert options using the preferences window. To
access, use menu "File" ==> "Preferences" and go to the "AIS"
at real size":
If this option is checked, targets for which dimensions are known will
be displayed at real size when the zoom factor is sufficiently
- The "Security
can be expressed in "NM" (Nautical miles), "KM" (Kilometers), or "M"
(Meters). This unit is also used for the minimum distance to show CPA
vectors (see below)
-The MMSI number only needs to be given if you
have a transponder on
board. The MMSI number entered in this field will be ignored by
ScanNav. If you do not enter it, you will have collision alerts with
your own boat. If you just have an AIS receiver, you can just leave
this field to 0.
-"Erase targets older than" : Targets will disappear from screen if they do not send any information
after the given value in seconds. (They will independently also change
color after 10 seconds without reception)
- An alarm will be triggered if
the option "Collision
alerts" is checked, and if the target's CPA or TCPA are below the given
values in "security distance" (for CPA), or "minutes before..." (for
TCPA). (here 1 nautical mile for CPA and 30 minutes for TCPA)
- Alerts may be audible ("Audible
alarm") and/or visual ("Show
alert box"), and the alert window may stay opened or close
after the alert conditions are safe ("Auto close"). On
another side, targets in alert condition are highlighted on
screen to distinguish them more easily.
alerts to targets with speed higher than": lets you ignore targets that are
at mooring or below a given speed (very useful in or near harbors)
- "Delay on validation"
lets you ignore alerts from a given target for a given period, once the
alert box is validated. (this option can also be changed in the alert
box when it appears before closing it).
-The length of the Heading line can be set
according to time. It can also be graduated in time steps as
your own boat (but independent parameters). A corridor with a width
proportional to the target's length can also be shown.
- If "Memorize tracks"
is checked, all targets positions are logged as tracks for the current
session. These tracks will be displayed or not according if you check
or not the "Show tracks"
- A "Maximum time"
value can be set to limit the visible section of the AIS tracks to a
given amount of time since the last known position. This will avoid an
overloaded display, still keeping the essential information. The
full tracks may be recovered at any time by unchecking the option.
If "CPA vectors"
is checked, a vector will be drawn between your own boat and targets to
show the estimated position of both boats at the time where
will be the closest to each other.
You can therefore see on the example at the left, that your own boat
(in blue) will pass behind the AIS target.
have a lighter display, you can limit the CPA vectors to targets for
which CPA is lower to given distance, by checking "Limit to" option,
and entering a distance value (in same unit as "security distance")
When checked, ScanNav will estimate the position of targets that do not
emit anymore, according to their last known position/heading/speed. In
this case, the target is shown at it's last known position, and a first
segment with a dashed line will show the estimated route done since.
The estimated position is therefore at the end of the dashed line
You may view all targets as a text list using menu
/ ARPA" ->"Targets
list" , that will be displayed as
- All available information for each target are
displayed as separate columns.
- The list has the same general behavior as the objects
list view or charts library (ordering, etc...)
- You may click on the "Columns" button to configure
the display (change the ordering, or add/remove columns)
- You can sort the list according different criterias
by clicking on the columns headers.
- Targets that are in collision alert will always
appear in red and at the top of the list
- Selected lines (highlighted in blue when clicking on
show up on the chart in a different color to distinguish them (you may
use "Ctrl" and "Shift" keys to select several lines)
- "Center" button will center selected targets on the
several lines are selected, ScanNav will modify the scale so as all
selected targets show up on the chart.
- "Properties" button will open the alert dialog of the
- When option "Filter old targets" is checked, only
targets will be displayed in the list (see preference settings above)
- When right clicking on the map at the position of an
all targets intersecting this point will be listed at the end of the
menu. Selecting one of these entries in the menu will open
list view with the corresponding entry selected.
ARPA / MARPA
Starting from version 10.1, the AIS module also lets you
Radar with an ARPA or MARPA interface, with equivalent functionality.
ARPA/MARPA targets will be distinguished from AIS targets in the list
view by their name, starting by "ARPA" and followed by the target
number. Supported ARPA sentences are:
- "TTM" (Tracked Target Message) or "TLL" (Target
Latitude and Longitude) : to report radar targets positions
- "RDS" (RADAR System Data) : to display the Radar
cursor on screen
Import of SSN
position reports for tracking
- The AIS module also lets you visualize SSN position
for tracking fishing fleets. Boats are visualized as AIS targets
including their tracks.
- To import SSN reports, use menu "File" -> "SSN
position reports import"
Several connection possibilities exist according to you
- When possible, plug your GPS to the AIS receiver,
then the AIS
receiver to your PC with ScanNav. In this case, and if supported by the
AIS receiver's possibilities, it will send the GPS positions together
with it's own sentences. In this case, you just have to modify the
settings in the GPS tab of the ScanNav preferences, to position the
speed at 38400bds. although most AIS boxes only retransmit GPS data, a
few also retransmit any NMEA data received from a
- Some AIS hardware also include an integrated
GPS (case of most transceivers). In this case, you might not
an additional GPS if the AIS retransmits the GPS info. The
configuration is in this case the same as 1 above.
- In other
cases, you will need to plug your AIS hardware on another independent
port. In this case, you need to configure a specific instrument in the
"Instruments" tab of preferences. The speed parameter should be
positioned to 38400bds. At the opposite of other NMEA instruments that
send information continuously, some AIS receivers only send information
when a target is in view. This can be interpreted by ScanNav as a low
reception alarm. In this case, you should give very high values to
"Communication timeout" and "Valid sentence timeout" parameters to
avoid raising useless alarms. These timeout values being in seconds,
you should enter very high values (for example 3600 for one hour, or
86400 for 24h)