New: Version 1.1 Click here for new features
Have you ever looked around, at sea, and been startled
by the sight of a ship close by, and bearing down on you? Modern ships,
especially passenger ferries, travel fast, and unless you keep a very
vigilant lookout, they can appear out of nowhere!
AIS (Automatic Identification System) is a system of VHF transponders carried by commercial ships and by some smaller vessels. Each vessel broadcasts it's position, course and speed, and other useful information, which can be plotted on the digital chart. Together with your own GPS information, AIS can be used to alert you of a potential collision with a ship.
The purpose of PocketAIS is to provide the recreational boater with an additional tool to help keep clear of commercial shipping. With the audible collision alarm, the device will beep when your present course will pass too close to a ship.
The software can be downloaded here, and is a free add-on for existing Memory-Map Professional uses.
Remember that many vessels are not equipped with AIS transponders, and the hardware and software used to transmit, receive and plot the vessels may be prone to failure. Please exercise good seamanship, and keep a lookout at all times. To determine manually whether a vessel is on a collision course, take a series of bearings of it with a hand bearing compass. If the bearing is steady, you are on a collision course.
When you are navigating near large ships, remember that they may have very limited ability to maneuver. What seems like the wide open sea to you, may be a narrow, shallow, congested waterway to the ship. Never assume that you have right of way over a ship. If you are on a collision course, you should give way by making a large alteration of course, so your intentions are clear.
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See ships plotted on the chart |
Greater situation awareness |
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Audible collision alert |
You don't have to watch the screen all the time |
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Find the ship's name, radio callsign, size, type of ship, size, rate of turn, destination port and ETA |
Aid in identifying a ship and predicting what they will do |
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Velocity vector shows ship's course and speed over ground on the chart |
Visual aid to judge how ships will pass |
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Table showing all ships sorted by name, distance, bearing, closest point of approach, or time to closest point of approach |
Find a specific ship fast in busy waters |
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Ships are color coded to show status and possible collision |
Attention is drawn to ships that might be dangerous |
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Shows class A (commercial ships) and class B (voluntary) AIS transponders (if supported by the receiver hardware) |
Shows all available vessels |
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Use a Pocket PC as an inexpensive, low-power, sunlight-viewable display at the helm (with waterproof case for outdoor mounting) |
Affordable and practical on smaller craft |
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Works on the PC, as well as Pocket PC |
Use in the wheelhouse or nav station |
You can run a simulated demo on your computer or PDA, without any additional hardware.
To receive and decode the AIS signals, you need an AIS receiver that outputs the AIVDM sentence on an NMEA or RS232 output. You also need a GPS to provide your own position, course and speed.
Some examples of compatible AIS receivers are:
NASA Marine (available in the USA from Si-Tex)
We suggest you connect your GPS to the input of the receiver, or use a receiver with built-in GPS. This provides the GPS data (RMC sentences) combined with the AIS data on the output.
You can, alternatively, connect the AIS and GPS on separate serial ports (or using separate Serial-to-USB adaptors). You could also connect the AIS, GPS and other instruments via a multiplexor with AIS input capability (eg, MiniPlex-Lite). Note that you cannot use a regular NMEA multiplexor, because the AIS receiver typically outputs at 38400 baud, whereas other instruments use 4800 baud.
You can also consider using a bluetooth serial adaptor. This will allow you to use a PDA with a wireless connection anywhere on the boat.
PocketAIS runs on Windows XP/2000, and on Microsoft Pocket PC 2003 or later. You need a Memory-Map Professional license. If you already have a Memory-Map Navigator or Discoverer license, you can upgrade here. If you would like a free temporary evaluation, contact support@memory-map.com.
To get started you need to download two files: the latest version of Memory-Map Navigator, and the AIS add-on.
MMNav Click here to Download
PocketAIS Version 1.1 Click here to Download (1 MBytes)
First install Memory-Map Navigator. Install some charts, and set up your GPS. Enter your Professional license key, and click the Help/About menu to ensure that the Pro features are enabled. Then install the PocketAIS add-on.
If you are using a Pocket PC, run the AIS application on your desktop PC (Start / Programs / Memory-Map / AIS). In the AIS application, click PDA / Install PocketAIS, and follow the standard Pocket PC installation prompts. From this point, use on the PDA and PC are identical.
GPS and AIS on the same COM port
If you have Memory Map Navigator or Pocket Navigator configured to use the same com port, you will need to disable it: go to the GPS Setup dialog and select "None" for the manufacturer.
In the AIS application, click Menu / Connect. Select the com port on which the AIS data is received, and set the baud rate (typically 38400 for AIS). The AIS application will pass the GPS information over to Memory-Map, so you will see your position on the map, even though the GPS is set to None.
GPS and AIS on separate COM ports.
Setup Memory-Map Navigator or Pocket Nav to use the GPS, as normal.
In the AIS application, click Menu / Connect. Select the com port on which the AIS data is received, and set the baud rate (typically 38400 for AIS). The AIS application will obtain GPS information from Memory-Map.
Demo Setup with no AIS receiver or GPS
Tap Menu / Connect, Check "Simulation", and click the Browse (...) button. Browse in one of the sample data txt files.
You should see targets listed in the AIS application. You don't yet have an own-ship GPS position, so the Dist,Bearing,Closest Point of Approach and Time of CPA are all blank.
Switch to MMNav/Pocket Nav to see the targets on the map.
Draw a track crossing the path of some ships, right-click > Operations > GPS Demo (or use the interactive GPS simulator on the PC). Switch back to PocketAIS, and (as the targets get updated) you will see the other data filled in.
Maneuver the simulation to put yourself on a collision course to experiment with the collision alarm.
The Dover samples are only a few minutes worth of data - so the ships keep jumping back when the file loops.
In the AIS application, you can view a list of all current targets, with their distance and bearing from your current position, and the distance and time of the closest point of approach.
You can sort the targets by clicking on the header of any column.
Clicking on a target shows you the full details in the area at the bottom of the window.
If the target is moving away from you, the CPA distance and time are blank.
The AIS targets are shown on the chart as animated icons. Each vessel is shown as a triangle, oriented according to its compass heading.
Each moving target has a velocity vector that shows its course and speed over the ground. All the velocity vectors are drawn on the same time scale, so you can judge the relative speed of different targets. You can determine, for example whether you will pass ahead or astern of a ship by looking at the heads of the velocity vectors.
For example, in the situation above, you will pass close ahead of the first ship, and well behind the second one.
The ship colors are as follows:
Targets with status "Moored" or "Anchored" are shown in grey.
Targets with a status "Restricted Maneuverability", "Constrained by draft", or "Aground" are shown in purple.
Targets "Under way using motor" are green.
Targets "Under way Sailing" are blue.
Targets on a collision course are red.
Targets nearly on collision course are yellow.
If no transmission has been heard from a target in the last 4 minutes, it is white.
If you have the "Data" button enabled, tapping, or hovering with the mouse will show the pop-up data on the target.
If no data has been received from a target in 10 minutes, it is automatically deleted. If you want to keep a record of all targets, go to the Settings dialog in the AIS application, and enable the "Record tracks" option. This shows the tracklog of all ships and prevents them from being deleted. In a busy area, your chart will quickly become congested, and may cause the display to flicker. We suggest you delete unwanted tracks, or at least hide them, as they carry quite a high overhead.
The software uses the course and speed of each target and your own course and speed to calculate your closest point of approach. If this is less than a given threshold, a warning is given. When you are on a collision course, the device will beep and the collision targets are shown in red.
Targets near the threshold are shown in yellow.
You can adjust the closest point of approach threshold, in terms of time and distance in the Settings menu. Targets that will pass closer than the specified distance, and within the specified time, are considered dangerous. These cause the beep and red target color. The time and distance thresholds are both doubled for the yellow warning targets.
Note that the size of the each ship (LOA) is added to the threshold, so you will still get some alarms if you set the distance to zero. If you want to disable the collision detection feature, set the time to zero instead, or just disable the beep.
If the alarm is beeping, there are three ways you can stop the alarm:
Turn your vessel or adjust your speed so you are not on a collision course
Mute the speaker output on your PDA or PC
Tap Menu / Settings and disable the beep (or adjust the thresholds)
If you want to see, and record, the raw data coming from the AIS, proceed as follows.
Click Menu / Pages.
Click Add
Select "NMEA Data Stream" and click OK.
If data is being received, you should see it scrolling up the window now
To record the data to a file, click Menu / Log file... and enter the name of a txt file the raw data should be written to. To stop data capture, click Menu / Log file and Cancel. The captured log file can be used as a simulation input to replay the data.
To see the decoded AIS messages:
Click Menu / Pages.
Click Add
Select "AIS Data Stream" and click OK.
Again, if data is being received, you should see it scrolling up the window now. You can capture a log file in the same way, but this data cannot be used as a simulation input.
When you have added these data "pages", you can toggle between them, and the original target list with the <<Page and Page>> buttons.
Version 1.1
Support for own-ship data from Pilot Plug.
Better indication of ship's heading.
When you zoom in on a large-scale chart, ship outlines are shown true-to-scale.
Improved support for static data on Class B vessels.
When a ship provides rate-of-turn, velocity vectors are shown curved to predict the path of the ship. (PC only, not PocketPC).
AIS is a very new technology in recreational boating, and we welcome any comments or questions you have about this software. Send them to support@memory-map.com