Category: Marine

New RTL-SDR software: rtl_ais

Over on we’ve seen news of a user who has worked to combine rtl_fm and aisdecoder into a single command line program called rtl_ais. AIS stands for Automatic Identification System, and is used in the marine industry to broadcast vessel GPS coordinates to one another to work as a collision avoidance radar system. With the correct software and an RTL-SDR, nearby boat AIS broadcasts can be received and the boat GPS coordinates plotted on a map.

Until recently, to decode AIS you had to pipe the AIS audio from software like rtl_fm or SDR# into a decoder. rtl_ais is a decoder which allows you to directly connect to the RTL-SDR and decode AIS without the need to pipe audio. The software is compatible on Linux and Windows and the current source code and Windows binary release is available at

The RTL_AIS help screen
The RTL_AIS help screen

AISRec for Android: New AIS Decoder

Back in December last year we posted about Jane feverlay’s work on his software called AISRec, which was a Windows AIS decoder for the RTL-SDR that he had developed.

AIS is an acronym for Automatic Identification System and is a system used by ships to broadcast position and vessel information. By monitoring AIS transmissions with the RTL-SDR we can build a boat radar system. We have a tutorial on this here.

Now from YouTube it looks as though Jane has developed a new Android version of AISRec which he describes as a high performance dual-channel AIS receiver for use with a single RTL-SDR dongle. The features of AISRec include:

1. Functions include AIS and GPS NMEA I/O, from/to USB devices and serial ports (special android devices with serial ports).
2. It supports TCP server and UDP forwarding jointly or independently for AIS and GPS.
3. It supports steaming in WIFI in AP or station modes and Ethernet.
4. It supports auto run on boot for especially rooted devices.

He also writes that AISRec also has companion implementations for Windows desktop and metro, Linux on Raspberry Pi 2 and the Radxa pro.

Unfortunately, at the moment there does not seem to be a link available to download the software and the video may only be a preview. The video does link to his Taobao shop at (in Chinese use Google Translate), which is where he might release the software when it is ready.

AISRec for Android. (rtlsdr, AIS)

New Windows AIS Decoder For the RTL-SDR: AISRec

Over on YouTube user Jane feverlay has uploaded a video showing a new AIS decoder called AISRec for Windows that he has developed.

AIS is an acronym for Automatic Identification System and is a system used by ships to broadcast position and vessel information. By monitoring AIS transmissions with the RTL-SDR we can build a boat radar system. We have a tutorial on this here.

The new software is not free, but he offers a trial version that limits the run time to 20 minutes and 5000 max messages. The paid version removes these limits and also decodes both AIS channels simultaneously. The program monitors data from the RTL-SDR and sends decoded data out via UDP. Software such as OpenCPN can then be used to display the AIS data on a map.

We tested the trial version on our machine and found that it worked well at decoding AIS messages. To download the trial go to and enter the code kn44. The download site is in Chinese, but it is obvious where to enter the code. We found the software to be virus free, but remember to always scan unknown software like this yourself. The full price of the software is unknown, but purchasing instructions are given in the trial download readme. The author also writes that his software now supports the Airspy, but not in the trial version.

Note that we discovered that the software doesn’t use a PPM correction setting as expected. Instead it uses a frequency shift setting. To set the shift in the AISRec.ini file, we had to calculate freqshift = 162.025 MHz – frequency of the second AIS channel as shown in SDR# with no PPM correction set.

Another similar software program that was released earlier is PNAis.

Airspy RTL SDR RTL-SDR RTL2832: AIS software receiver for airspy and RTL2832 USB dongles

New AIS Decoder for the RTL-SDR: PNAIS

Over on our Forums  has told us about his recently released an AIS decoder called PNAIS which appears to directly connect to the RTL-SDR and decode AIS data. After decoding it then outputs the decoded NMEA data via UDP, which could then be received and used in map plotting software such as OpenCPN.

AIS is and acronym for Automatic Identification System and is a system used by ships to broadcast position and vessel information.

PNAIS Decoder

Hak5: Identify and Locate Ships Via AIS Transmissions

Hak5, a popular YouTube technology show has recently been dedicating a bunch of episodes to RTL-SDR projects. Recently we posted about their efforts with ADS-B, and some GNU Radio tutorials. Their most recent video discusses AIS (Automatic Identification System) which is a system similar to ADS-B which ships use to transmit their location to create a modern GPS based radar system.

The Hak5 video discusses how AIS works and also shows how to use an RTL-SDR to receive it. In their tutorial they use SDR#, VBCable and ShipPlotter to receive and view AIS data on map. Note that we also have an AIS tutorial here.

Identify And Locate Ships Via AIS Transmissions!, Hak5 1610

K2NCC’s Guide to AIS Reporting for the RTL-SDR

AIS enthusiast K2NCC has posted in our forum a link to a PDF document he has created showing how to use SDR#, AISMon and AIS Dispatcher to report AIS data to and and are websites which aggregate AIS data from various contributors around the world.

AIS is an acronym for Automatic Identification System and is a type of modern GPS based radar system similar to ADS-B used by mariners to help avoid collisions at sea.

Map from
Map from

Decoding 2x AIS Channels with SDR Console, AISMon and OpenCPN

YouTube user k2nccvids has posted a video showing him decoding and plotting both AIS channels simultaneously on a Windows PC with free software. To do this he uses SDR Console and two AISMon instances. SDR Console is a general purpose SDR GUI that supports the RTL-SDR. One of it’s major advantages over other SDR software is that it can tune to multiple signals in the same swath of tuned bandwidth simultaneously and output their audio to different virtual audio cables.

k2nccvids used two AISMon instances, each one connected to a separate virtual audio cable outputting AIS audio from SDR Console. He set AISMon to output decoded UDP packets on two different ports. Then he created two UDP listeners in OpenCPN for plotting, one for each port.

2-Channel AIS Receiver with RTL-SDR and GNUAIS

Blogger OZ9AEC has written a post on his blog showing how he made a 2-channel AIS receiver using the RTL-SDR, GNU Radio and GNUAis. AIS is a radio protocol used by boats to broadcast their position and speed which is then used to create a type of radar system to help avoid collisions. AIS signals are transmitted periodically on one of two channels. Two channels are used to improve capacity and help avoid interference if two signals from different boats are broadcast at the same time.

Before this, most AIS receiver implementations we’d seen that used the RTL-SDR received only on a single channel. OZ9AEC’s GNU Radio program receives on both channels simultaneously like a commercial AIS receiver does and is thus a better receiver. He eventually plans to get this receiver to run on a Beaglebone.

See his post for instructions and to download the GRC files.

Update: Another AIS decoder known as gr-ais is also capable of 2 channel AIS, and bristromat from Reddit has written a tutorial on setting it up and running it with OpenCPN.

Two channel AIS Block Diagram