Tagged: marine

Ships: New RTL-SDR Compatible Android App for AIS Reception and Plotting

Today an Android app programmer sent a message to let us know about his new open source RTL-SDR compatible AIS app called Ships.  This is a free app that allows you to decode AIS signals, and plot them directly onto an OpenStreetMap/OpenSeaMap or output the data via UDP to another mapping program.

Ships also has another interesting feature which is that it will automatically determine the PPM offset of a dongle, meaning that generic dongles without TCXO’s can be easily used for AIS. It appears to do this by using the AIS signals themselves, so you will need sufficient AIS traffic in your area for the calibration to work.

AIS stands for Automatic Identification System, and is a system used to track the locations of marine vessels. It is similar to ADS-B in that nearby ships can be plotted and tracked on a map by using an RTL-SDR as the receiver. We have a tutorial for PC available here.

The app can be downloaded for free on Google Play, and the open source code is available on GitHub.

Ships RTL-SDR Android App Screenshot
Ships RTL-SDR Android App Screenshot

Setting up a Raspberry Pi Based AIS Receiver with an RTL-SDR

Over on YouTube user Tobias Härling has uploaded a video showing how he used a Raspberry Pi and RTL-SDR dongle to set up an AIS receiver. AIS stands for Automatic Identification System and is a radio system similar to ADS-B which allows you to create a radar-like system for boats. For Windows we have a tutorial on AIS reception here.

In his setup he uses rtl_ais and the kplex software and shows how to install everything from scratch. He also shows how to set the system up so that decoding automatically starts up and begins outputing NMEA data through the network when the Raspberry Pi is powered on. This way an a device like an iPad could be used to run OpenCPN to view the plotted ships.

AISRec Updated to Version 2.1

AISRec is an RTL-SDR (and now Airspy) compatible AIS (automatic identification system) dual channel decoder. 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.

Last time we tried AISRec we found its performance to be very good, with it decoding more messages than other software we tried. The new version includes the following updates:

  • Added auto detection of devices when devices are plugged in.
  • Added the support for airspy. Allow selection of devices by serial number for rtlsdr dongles.
  • Added AISRec core 3.0. The new core is 2x faster than AISRec core 2.0.
  • Added one embedded multi-user TCP server. Any client works with AISRec should implement auto reconnection.
  • Added auto display of local IP for the TCP server.
  • Added one output to one serial port.
  • Added interactive changes of gain parameters for devices.
  • A few changes on GUI.
  • Added an icon for GUI. Users should reset the windows icon buffer to allow the display of the new icon.

In addition, while AISRec hopes to be commercial software one day, at the moment they are currently offering free registration. See their FAQ for information on registering for free.

AISRec running with OpenCPN.
AISRec running with OpenCPN.

Using AIS Share, OpenCPN and an RTL-SDR on a Sailboat

AIS Share is an app for Android that allows you to turn an Android device into an AIS receiver by using an RTL-SDR. AIS stands for Automatic Identification System and is used by ships to broadcast their GPS locations, to help avoid collisions and aid with rescues. An RTL-SDR with the right software can be used to receive and decode these signals, and plot ship positions on a map.

AIS Share is a dual channel decoder that outputs decoded NMEA messages via UDP, so that plotting software like OpenCPN can be used to display the ships on a map. AIS Share had been around before in another form known as rtl_ais_android which we posted before, but this version of AIS Share is a newly updated and improved version that now includes a very nice GUI. The app costs about $2 and is available on the Google Play store, but there is a demo available that will work up until 1000 messages are received. You will need an RTL-SDR and a USB OTG cable to run the app.

Recently the author of the app received word from a user called Harmen who has successfully been using his AIS Share app on his sailboat. Harmen uses the app on an Android tablet which is enclosed in a waterproof box. For an antenna he uses a coax collinear.

In the future the author writes that he’d like to update the app to support things like the ability to change more dongle settings like bandwidth/sample rate and add the possibility of using the internal phone/tablet GPS. He is also open to any community suggestions.

AIS Share Receiver on the sailboat in a waterproof case.
AIS Share Receiver on the sailboat in a waterproof case.
The back of the Android Tablet, showing the RTL-SDR and the antenna connection.
The back of the Android Tablet, showing the RTL-SDR and the antenna connection.
The AIS Share main screen GUI.
The AIS Share main screen GUI.

https://www.youtube.com/watch?v=ApGk8P82THs (Unfortunately the video has been removed)

A new AIS Decoder for the RTL-SDR on Android

A reader of our blog, EBC81, has written in to let us know about a new RTL-SDR based AIS decoder that he has written for the Android OS. AIS stands for Automatic Identification System and is used by ships to broadcast their GPS locations, to help avoid collisions and aid with rescues. An RTL-SDR with the right software can be used to receive and decode these signals, and plot ship positions on a map.

EBC81’s program is called rtl_ais_android and can be downloaded from this GitHub link. It decodes the AIS data into NMEA messages, which can then be sent via UDP to mapping programs in Android or a program like OpenCPN on your PC. To use the app you will need a USB OTG cable to connect your Android device to the RTL-SDR.

In the future EBC81 hopes to create a second app which will display the ship positions on a map.

NOAA Weather Satellite Antenna and Software Guide

Over on the SDR for mariners blog, author Akos has written two new beginners posts on getting up and running with receiving and decoding NOAA weather satellite APT images.

The first post discusses antennas that are useful for NOAA satellite reception, and shows how to build a homemade turnstile and QFH antenna. His second post shows a beginners guide to the software that can be used to decode the APT signal in order to obtain a live weather satellite image.

sdrformariners_apt_image QFH Antenna

Software Defined Radio for Mariners: AIS Antenna Design Review

On a new blog called ‘Software Defined Radio for Mariners‘ aimed at mariners wanting to get into cheap software defined radio with the RTL-SDR, the author has posted an article for beginners on choosing a type of AIS antenna to build.

He reviews the performance of multiple homemade AIS antennas with his RTL-SDR, and finds that a Monopole antenna with two radials gave the best value/performance trade off.

He has also written a hardware guide article, explaining some of the most common antennas adapters and cable ends that might be found.

AIS Monopole Antenna

RTL-SDR Tutorial: Cheap AIS Ship Tracking

Large ships and passenger boats are required to broadcast an identification signal containing position, course, speed, destination, and vessel dimension information to help prevent sea collisions. This system is known as the “Automatic Identification System” or AIS for short. There are dedicated AIS receivers intended to be used on boats, or by hobbyists, but they can be expensive. A radio scanner, or the cheap RTL-SDR software defined radio (or a more advanced SDR such an Airspy) can be used to receive these signals, and with the help of decoding software, ship positions can be plotted on a map.

This tutorial will show you how to set up an AIS receiver with the RTL-SDR. Most parts of this tutorial are also applicable to other software radios, such as the Funcube dongle, Airspy and HackRF, or even regular hardware scanners if a discriminator tap is used, but the RTL-SDR is the cheapest option.

Safety Warning: This probably should not be used a navigational aid on a boat as the field reliability of the RTL-SDR or other software radios is not proven. This guide is intended for land based scanner hobbyists.

Note, tracking ships with AIS is very similar to tracking aircraft with ADS-B, which is another project that may interest you.

Examples of AIS received with RTL-SDR

An AIS radar example is shown by YouTube user Vinicius Lenci who uses an RTL-SDR, SDRSharp and ShipPlotter. This video also shows what a strong AIS signal sounds like.

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