I stumbled across @abcd567’s post on running a dual ADS-B and AIS receiver. There is a whole parallel community of people running AIS feeders for marine traffic, tracking vessels, doing the same as what we do here with PiAware for aircraft.
Since I had a spare Nooelec SMART SDR, a Pi4 and a Slim Jim airband antenna, I decided to take a look at the AIS software mentioned in the post. AIS-catcher installed on Pi OS no problem and includes a web front-end with some stats and even a basic map similar to SkyAware. I also found some useful Windows software (Ais Decoder) which is helpful for debugging the NMEA messages from the logs.
I didn’t get any vessels or messages but didn’t really expect to with an indoor antenna of the wrong frequency (121 MHz airband vs 162 MHz AIS) and being a fair distance from the coast. But I happened to leave it running and earlier today it lit up with AIS messages.
It turned out to be a helicopter not far away. I could see it on the maps in both AIS-catcher and PiAware, evidently with transponders for both ADS-B and AIS. It was in fact a Coastguard Search And Rescue (SAR) helicopter (this one). FlightAware shows it as having done a large circuit round here in the north-west and Wales. Maybe on a test flight?
It would make sense for SAR helos to be AIS/Marine radio equipped. It would enable them to find vessels in distress(as well as nearby vessels), communicate with them and for the vessel to be able to see their position.
Indeed, looks like I chose the perfect time to run it, since I wasn’t expecting to see anything, it was just a play with the software. The Manchester Ship Canal isn’t too far away so maybe that will show an actual ship at some point.
You have to determine how much is ppm drift of your dongle, and set that value in config file.
When i tried initially, i was not aware of importance of ppm. I used a generic dongle. There were no ships and no messeges received by my receiver.
Later when I determined ppm drift of generic DVB-T (black $10), it was 38 ppm. I then used this value in config file, and suddenly the map started showing vessels and status showing heaps of messages.
Aye, you mentioned that in your original guide which was very helpful. The ppm offset on this dongle ended up as -1. It’s worth forcing your chosen sample rate too. So if in AIS-catcher you have -s 2304k then in the rtl_test include -s 2304000.
It’s a Nooelec NESDR SMArt v5 (datasheet) which has a temperature controlled oscillator and a SMA connector, so useful for hooking up to existing kit without needing a MCX pigtail. It doesn’t drift as it gets warm. I got it to explore with Cubic SDR and built the airband antenna to listen to the nearby aircraft. It’s also a useful temporary backup for the Pro Stick Plus in case ever needed. I’m very pleased with it.
Your mentioning this has made me wonder if the blue Pro Stick Plus also has a ppm offset. I see there’s an advanced option for it in the SD-card PiAware. I’ve never thought about it until now. Maybe it’s been a bit out all these years!
Very nice – are you using the same Pi or machine to receive both, and do you have an antenna for each installed the same way (eg on a roof)? Just curious.
No, I tried running multiple programs on a single Pi and didn’t think it worth the trouble. When I started Pis were cheap and plentiful so I found it easier to just go and buy another Pi or use something else like a Virtual Machine on a desktop or an HP Thin Client (HP T620) running Ubuntu.
ADSB uses a Flightaware antenna and AIS uses a Diamond 2/70cm VX50 amateur radio antenna.
I was about 15-20km from the plane but you can see ships on the surface around the same distance.
In some cases SAR helicopters are performing other maritime tasks other than emergencies. I regularly now see the Coastguard SAR making meandering loops over the area and surmise that summer weather = more boats on the water = more people doing stupid things on the water. They are trying to get ahead of the accident curve.
Another example happened a couple of weeks ago when Delta 205 had bird strike after takeoff and requested an immediate return. It had to dump fuel to do so and a Coastguard helicopter was on scene just like that to monitor the event. Everything was OK in the end.
There is usually a Huey or Herky Bird within sight of my patio most of the time. I’m about 7 miles from the end of the runway for the largest USCG Air Station.
