A lot of AIS decoding applications are paid software, but it's possible to use a combination of two free programs and track maritime ships for free!
The demodulator part is an application is called 'AISmon' and can be fed with sound output from your SDR program via Virtual Audio Cable/VB Cable. Once the AIS packets are demodulated, they are forwarded via UDP port 29421.
The decoding part is an application called 'AIS Decoder' and can be configured to use UDP port 29421 as an input. In the settings of this program, you can instruct it to only decode positioning information from the vessels.
After a little while, two more windows will appear containing the information decoded from AIS transmissions from various ships. The two frequencies to monitor are 161.975 and 162.025 mHz. Being VHF, I imagine you would have to be located fairly close to a coastal region or near a busy shipping port to receive anything useful.
AIS Decoder can supposedly output ship names and positions to a .KML file which can be used to overlay them on a Google Earth map, but I couldn't figure out how to do that.
Thanks for watching.
HARDWARE
-Airspy R2 SDR
-Diamond VX-1000 Antenna
-LMR400 Feedline
SOFTWARE
-SDR Sharp 1702
-VB Cable
-AISmon
-AIS Decoder
