While Automatic Identification Systems (AIS) have been appearing on more commercial and recreational vessels, many sailors still find it to be cost-prohibitive. As an alternative, I recently used a combination of smartphone apps and AIS websites to watch vessel traffic during a sail from Catalina Island. Though other boats couldn’t see me on their chartplotters, I could see where my boat fit into the traffic by using websites, and I found it to be very helpful and better yet, free.
To display my boat’s AIS information, I installed Mobile AIS (mAIS), a free app from MarineTraffic, registered my email address, and entered my vessel’s MMSI number. The app broadcasts AIS information over the web using the smartphone’s GPS position and cellular data networks. Once loaded, I clicked “Start” to begin reporting my position, including our status, position, course and speed. Periodic position updates continued until I selected “Stop.”
Within a few minutes, we were able to view our vessel on MarineTraffic.com, which maintains a worldwide network of AIS receivers In theory, the data is shared by a number of AIS sites, though there may be delays or vessel information may be out-of-date. In practice, we found MarineTraffic to be quite accurate. Since this data was not being transmitted through VHF radio frequencies, our AIS information was not displayed on the chartplotters of nearby vessels, only on websites. So even though we could see our boat and nearby boats on the web, we were not visible on their AIS.
In addition to viewing AIS online, there are several apps that display it. Ship Finder ($4.99), MarineTraffic ($3.99) and Boat Beacon ($9.99) display real-time AIS vessel information as well as other useful features such as collision detection, man overboard tracking and anchor watch. Like mAIS, Boat Beacon transmits position data over the cellular data network.
By combining my AIS and MarineTraffic.com—both for free—I was able to use my smartphone to help navigate the busy shipping lanes. Of course, this is not a substitution for dedicated AIS, nor should it be used for navigation, but knowing the speed and distance of approaching container ships helped us navigate a safer crossing. Using this technique, groups of racers or cruisers could follow one another on-screen, something that could be especially useful for longer distance or multi-day events.