Floatr Pal

This is the companion piece to Floatr. It receives, decodes, converts and persists AIS messages received with your SDR.

Requirements

• An antenna and SDR. I highly recommend an FM notch filter and 162 MHz bandpass filter as well.
• nmea_plus
• AIS-catcher

Installation

In order for Floatr to work correctly, two services must run (I use systemd):

• decode-ais.sh uses your SDR to turn radio signals into AIVDM sentences with AIS-catcher
• log-ais.sh parses these sentences with nmea_plus and saves them to the database

You'll need to replace the following placeholders throughout:

• RAILS_APPLICATION_PATH - path to the Floatr application
• DECODER_PATH - path to AIS-catcher
• FLOATR_SERVICE_PATH - path to ais.rb (i.e. /usr/local/share/floatr/)
• RBENV_PATH - i.e. /home/username/.rbenv/shims/ruby

Ideally, the services work like this:

• Your antenna receives AIS messages...
• That are decoded into AIVDM sentences by decode-ais.sh...
• And echoed to port 4159.
• The output of this port is then piped into log-ais.sh...
• Where it's parsed into Active Record objects by ais.rb...
• And saved to the database for the Rails application to consume.

Note that it's possible to replace decode-ais.sh with any stream of AIVDM sentences (from another service, STDIN, etc.)