AIS-catcher and Collision Detection

[tkreyche]

Has anyone implemented AIS-catcher on a boat, with the data feeding into collision detection software? This system would be independent of cloud-based systems, such as Pocket Mariner.

Our local boating area (Puget Sound near Seattle) has fast ferries travelling at 30 kts, and quite a few other vessels at 20kt. When sailing, there are many things to look after and it's surprising how quickly these boats approach when you don't have a dedicated lookout.

There is already latency because the fast boats are only broadcasting AIS every 2 or 3 seconds. It's not clear what the latency is for Pocket Mariner and other web services. An onboard system would be more predictable and there is no advantage of having a range outside the immediate area.

It looks like SignalK has some collision detection plug-ins and I intend to check them out. I'm guessing I could use GNSS from my NMEA 2000 network and feed everything into SignalK.

thanks, Tom

[tkreyche]

Here's a way to do it using OpenCPN.

You will need to have AIS-catcher running on a computer on your boat, for example a Raspberry Pi with an RTL-SDR dongle with a basic antenna. A simple vertical dipole made out of coax would probably work fine.

Then you need a computer running OpenCPN. It could be on a separate computer such as a laptop. Almost certainly you could run both OpenCPN and AIS-catcher on Pi 5 (ideally with an nvme drive) and AIS-catcher on the same system - it's fast. Maybe it would work on a Pi 4B with a lot of memory.

Configure AIS-catcher to connect to OpenCPN - Jasper describes how to do this with the -u option.
Then configure OpenCPN to receive the data from AIS-catcher. Options for configuring OpenAIS are under Ships->Targets. See screenshots from OpenCPN version 5.10.2 (click to enlarge):

Connection Configuration

AIS Configuration

[tkreyche]

Another option is to use SignalK with a plugin

The AIS-catcher configuration is exactly the same as for OpenCPN.

The SignalK configuration is similar to OpenCPN. In SignalK, create a new data connection with Data Type of NMEA0183, source UDP and use the port number that you configured in AIS-catcher. There are only a couple of configuration items available in the plug-in itself: Collision Detection Distance and Data Timeouts. These are minimal compared to the AIS options available in OpenCPN, but it's not clear to me if the more complicated rules in OpenCPN are effective or useful.

The collision-detector offers a notifications.danger.collision subscription, which would allow someone to consume the data and write their own app, which could probably run on the same system as AIS-catcher and the SignalK server. There is no UI for the plug-in other than the configuration items.

Vessel positions can be viewed in SignalK using Signalk/Vesselpositions, GaladrielMap and probably other UIs. I don't see any additional collision specific options in these programs.

Someone looking for a complete solution would probably be best off using OpenCPN.