As the Raspberry Pi in its various forms continues to flow into the wild by the thousands, it’s interesting to see its user base expand outside beyond the hacker communities. One group of people who’ve also started taking a liking to it is sailing enthusiasts. [James Conger] is one such sailor, and he built his own AIS enabled chart plotter for a fraction of the price of comparable commercial units.
Automatic Identification System (AIS) is a GPS tracking system that uses transponders to transmit a ship’s position data to other ships or receiver stations in an area. This is used for collision avoidance and by authorities (and hobbyists) to keep an eye on shipping traffic, and allow for stricken vessels to be found easily. [James]’ DIY chart plotter overlays the received AIS data over marine charts on a nice big display. A Raspberry Pi 3B+, AIS Receiver Hat, USB GPS dongle and a makes up the core of the system. The entire setup cost about $350. The Pi runs OpenCPN, an open source chart plotter and navigation software package that [John] says is rivals most commercial software. As most Pi users will know the SD card is often a weak link, so it’s probably worth having a backup SD card with all the software already installed just in case it fails during a voyage.
SpaceX just concluded 2017 by launching 10 Iridium NEXT satellites. A footnote on the launch was the “hosted payload” on board each of the satellites: a small box of equipment from Aireon. They will track every aircraft around the world in real-time, something that has been technically possible but nobody claimed they could do it economically until now.
Challenge one: avoid adding cost to aircraft. Instead of using expensive satcom or adding dedicated gear, Aireon listen to ADS-B equipment already installed as part of international air traffic control modernization. But since ADS-B was designed for aircraft-to-aircraft and aircraft-to-ground, Aireon had some challenges to overcome. Like the fact ADS-B antenna is commonly mounted on the belly of an aircraft blocking direct path to satellite.
Challenge two: hear ADS-B everywhere and do it for less. Today we can track aircraft when they are flying over land, but out in the middle of the ocean, there are no receivers in range except possibly other aircraft. Aireon needed a lot of low-orbit satellites to ensure you are in range no matter where you are. Piggybacking on Iridium gives them coverage at a fraction of the cost of building their own satellites.
Put a message in a bottle and toss it in the ocean, and if you’re very lucky, years later you might get a response. Drop a floating Arduino-fied buoy into the ocean and if you’ve engineered it well, it may send data back to you for even longer.
At least that’s what [Wayne] has learned since his MDBuoyProject went live with the launching of a DIY drift buoy last year. The BOM for the buoy reads like a page from the Adafruit website: Arduino Trinket, an RTC, GPS module, Iridium satellite modem, sensors, and a solar panel. Everything lives in a clear plastic dry box along with a can of desiccant and a LiPo battery.
The solar panel has a view through the case lid, and the buoy is kept upright by a long PVC boom on the bottom of the case. Two versions have been built and launched so far; alas, the Pacific buoy was lost shortly after it was launched. But the Atlantic buoy picked up the Gulf Stream and has been drifting slowly toward Europe since last summer, sending back telemetry. A future version aims to incorporate an Automatic Identification System (AIS) receiver, presumably to report the signals of AIS transponders on nearby ships as they pass.
We like the attention to detail as well as the low cost of this build. It’s a project that’s well within reach of a STEM program, akin to the many high-altitude DIY balloon projects we’ve featured before.
When we first started hearing about software-defined radio hacks (which often use USB dongles that ring it at under $20) we didn’t fully grasp the scope of that flexibility. But now we’ve seen several real-life examples that drive the concept home. For instance, did you know that SDR can be used to track ships? Ships large and small are required by may countries to use an Automatic Identification System (AIS) transponder. The protocol was originally developed to prevent collisions on large ships, but when the cost of the hardware became affordable the system was also brought to smaller vessels.
[Carl] wrote in to share his project (which is linked above). Just like the police scanner project from April this makes use of RTL-SDR in the form of a TV tuner dongle. He uses the SDRSharp software along with a Yagi-UDA. The captured data is then decoded and plotted on a map using ShipPlotter.