AIS is a key component of any electronic charting system (ECS). In our course on Electronic Chart Navigation, we use qtVlm for our ECS. It has a sophisticated AIS presentation, plus a unique tool for accessing live AIS traffic internationally and interacting with them from your own real or simulated vessel. Here we want to outline the use of AIS in qtVlm. As with other features of this diverse program, there are options to be sorted out.
For background on the Automatic Identification System, known universally by the initialism AIS, please see Introduction to AIS.
How to get AIS targets onto the qtVlm screen
These notes are just how to turn it on; once on, what you see depends on several other settings, which we come back to.
(1) Simulation mode. To interact with the AIS traffic, and not just look at it, run a simulation. First, turn on AIS from the icon in the toolbar if not already on (bright green is on; gray is off), then move your boat to anywhere in the world you choose to be during the simulation, and then start a simulation.
You will then see AIS traffic within 50 nmi of your boat location. These targets are internet AIS, which we discuss below. This AIS traffic will show up essentially regardless of other AIS settings, as long as the AIS icon is turned on. Note the AIS must be turned on before starting the simulation; if turned on after starting, it will end that simulation, which you can start again, now connected to the AIS data server.
(2) View internet AIS. To see AIS traffic without simulation, move the boat to the chosen position, then in menu Configuration/AIS/Options turn on AIS via Internet. Then press OK to close that window, and at the base of the microboard, Start NMEA and the traffic will appear. Again, within 50 mi of your location and the AIS on icon must be turned on.
(3) Live AIS. We can also see live AIS targets on the screen from our own AIS receiver when sailing underway that we load into qtVlm. These would come into the system as NMEA sentences, so we would need to tell qtVlm the source of the input, which is done in menu Config/NMEA connections/Incoming.
When displaying your own live AIS reception, you can also turn on the AIS via internet shown above. With this on, you see both live AIS and internet AIS, where the latter are marked with a red dot. If there is a report from the same vessel from both your live AIS and the internet AIS then only the live AIS will show. The internet AIS targets can be delayed by a minute or more, compared to the much faster updates for live AIS, up to every 2 seconds (see Into article cited). Thus adding the internet AIS would be of most value for the more distant targets that your antenna might not be picking up.
The AIS showing in the simulation mode do not show the red dots because we know they are all internet AIS.
Figure 3. Live and internet AIS. The yellow and green boats are all vessels sending out AIS signals that are picked up not just by other vessels, but also by numerous land based AIS antennas, such as the one we have at Starpath HQ. These signals are then sent to one of several companies that compile them and then redistribute to users around the world via the internet. Marine Traffic and Vessel Finder are two popular examples. In qtVlm, internet targets have a red dot. Targets with black dots (symbolizing an anchor ball daymark) are those with an SOG below a user selected value. We cannot stress often enough that internet AIS are delayed signals, so they must be used with much caution. A target seen approaching you as an internet AIS vessel, could be well past you at this moment. A real, live AIS receiver is inexpensive and should be considered part of your minimum navigation equipment.
(4) Replay saved file. Another way to see AIS traffic is to replay a saved file of a NMEA stream of real data that you saved from a previous voyage, or someone else did, and then sent you the file to view.
(1) Yellow vs. green. This distinction marks how much data we have on the target. Yellow means we have just the dynamic data of position, COG, SOG, and heading if they have a heading sensor. This data is given every 2 to 30 sec, depending on the target. Green means we have the full set of static and voyage data. This data can take up to 6 minutes to update.
(6) Marks on the targets. As noted above, a red dot means it is an internet AIS target, but this is not shown in simulation mode.
A black dot on an AIS target means the reported SOG of the target is less than the user-set minimum speed indicated in the 7th line down of the options page above. A logical application would set this to zero or a few tenths of a knot, but it will mark the targets according to whatever speed is entered. If this option to hide them is turned on, it will then hide all targets below that speed.
A target with an engaged in fishing daymark (two cones, point to point) means this class A vessel has declared its navigation status to be vessel engaged in fishing. Below is a summary of these daymark icons. Remember that the navigation status that triggers these must be manually set by the vessel operator and it is not uncommon to see cases where they have not been updated properly.
Figure 7. Tooltip AIS info. A cursor over the target displays the tooltip info. If this were green it would include the vessel name. Also shown is the distance from our boat and the bearing to the target from our boat.
Figure 16. AIS display options, here focusing on ones that affect the CPA displays. See also Figure 2.
Figure 17. AIS set up display options, CPA/TCPA tab shown in yellow. Blue is on, so in this example all options are turned on with the indicated values.
Figure 22. Many targets being tracked. These could be cleaned up by limiting the maximum CPA to watch. Pictures like this can change notably with just slight changes in your course or speed. Also this type of picture is a good reminder that we must look out of the window and not just stare at the computer screen. It is easy to get mesmerized by such functionality in ECS and when looking at the many features of modern radar.