AIS-catcher
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Free live ship tracking, unfiltered

A live ship map fed by AIS receivers that volunteers run around the world with the open-source AIS-catcher software: no filtering, no delay, no paywall.

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What you can do here

Coverage Forum Documentation GitHub
Getting Started Guide Introduction to AIS What is new? Community Hub Reference Material

The AIS-catcher project

Live vessel tracking by a community of receivers — and the open-source AIS receiver behind it.

AIS is the radio signal ships broadcast with their identity, position and course. Thousands of volunteer stations pick it up and feed one live map: every ship they hear, as they hear it, with nothing filtered or delayed. The receiver behind it is our project since 2021: the best possible AIS receiver from a cheap software-defined radio dongle. Free and open source.

Live vessel tracking map Quick Start GitHub

The map

Live vessel tracking, unfiltered.

Every station on the network sends what it hears to one map, the moment it hears it. No paywall, no delay and no filtering: coastal traffic, inland waterways, fishing boats and pleasure craft alongside the container ships. Find any vessel by name, MMSI or IMO number and follow its position, speed, course, destination and track. Open a port to see what lies inside it, what is expected, and what arrived and left in the last day.

Live vessel tracking map Every ship the community hears, in real time, with its track, details and destination. Ports and terminals Vessels inside, expected, arrived and departed, for more than 6,000 ports around the world. Vessels The ships heard most recently: name, flag, type, destination and when they were last heard.

The software

AIS-catcher, the software.

What's sailing near you Every ship in range, live on your own map, and the day on replay. No expensive hardware needed. Radio and technology Take the easy route with a simple install, or dive in: the metrics are there to tune your station and squeeze out more. Harvest your own data Vessel data is hard to get and costly to buy, yet it is in the air around you. What your antenna picks up is yours — no license, no terms of use.

The decoder

Squeeze every message out of the signal.

Application size 3 MB, lightweight
Lightning fast written in C++
Extensive support RTL-SDR, AirSpy, …

Antenna height and location decide most of what you hear. Once those are fixed, the decoder is the only part of a station that can keep improving for free — and that is where most of the work has gone.

  1. 2021First generationAn FM discriminator, the way most dedicated AIS receivers do it. The baseline.
  2. 2022Second generationCoherent decoding: follows the phase through the whole message. A significant step up in messages over the first generation.
  3. 2026Third generationNew, improved algorithms, fine-tuned on real data. Up to 8 % more messages reported on some stations.

Measured, not claimed.

AIS-catcher can run several decoders on the same input at once and count what each one hears. That is how every generation was measured against the one before — on real signals from real stations, not a simulator — and the panels to do it yourself are in every viewer.

Details and settings in the decoder documentation.

Messages per hour over a day, second and third generation decoder Vessels per minute, second and third generation decoder Message gain per minute of the third generation over the second: about nine percent

The web viewer

See what you hear.

Every station comes with its own web viewer, feature-rich and highly configurable: the ships in range on a map, how far you reach in each direction, signal levels, message rates and the statistics of the station itself — with the map layers, colours, columns and panels all yours to set. That feedback loop is what makes a receiver fun to tune — move the antenna, watch the range plot grow.

The AIS-catcher web viewer in day mode: ship card, map and vessel table The same view in night mode

DayNight

  • Replay. Play back the last hours at up to 3600×, ships at true size.
  • Charts and tables. Configurable, with export of the data behind them.
  • Ticker. Arrivals, departures, new ships in range, safety messages — as they happen.
  • Places. Draw your own ports, berths and areas; see who is inside, arrived or left.
  • Aircraft too. Add an ADS-B feed and planes share the map.
  • Real time. A full-screen kiosk mode, and a fireworks mode that flashes every message as it lands.

Setting up

The antenna is the hard part. The software is not.

What you need: a computer, an RTL-SDR dongle and an antenna. Outside, as high as you can get it, with a clear view of the water — that is where the effort goes. The rest is easy on any common platform: start AIS-catcher in managed mode, a control panel opens in your browser, and a wizard takes it from there in four easy steps.

  1. 1 WelcomeThe control panel opens in your browser; on first start, the wizard.
  2. 2 Input deviceIt lists what it finds on the machine — an RTL-SDR, a dAISy-catcher, a receiver on a serial port. Pick yours.
  3. 3 Where the data goesThe community map, your own tools, other services — each a switch, all optional, all changeable later.
  4. 4 Save and startCheck the summary, save, and the receiver starts. Everything else lives under Input and Output.
Wizard step 1: welcome, with the Get started button Wizard step 2: choose the input device, an RTL-SDR selected Wizard step 3: choose where the data goes, then Next Wizard step 4: summary with the Save and Close button

The Quick Start takes you from zero to ships on your own map in about fifteen minutes, on whichever platform you have. If you get stuck, the community forum has seen most questions before.

Raspberry Pi Linux Windows macOS Docker Android

The data

Do more with what you hear.

AIS-catcher is a node, not a dead end. It reads from an SDR as happily as from other stations over the network, combines their feeds, filters them, and sends the result on in whatever shape you need — so you can build your own efficient network of stations, from one dongle to a whole coastline.

Every input and output has its own page in the documentation — inputs, outputs and what gets forwarded — and pip install aiscat gives Python the same decoder for files, streams and notebooks.

The community map

Connect with a community. Feed the map. One switch.

  • Sharing is off until you switch it on — a checkbox in the wizard, or a simple switch on the command line.
  • The ships your station hears go live on the map, unfiltered.
  • Your station fills in its patch of the coverage map and, if you want, gets a page of its own among the stations already feeding.
  • What leaves your machine: the AIS messages you decode and, if you want, your station's position. Nothing else.
Add your AIS-catcher stationRegister it and get a sharing key.
Connect an existing stationAny receiver or software that sends NMEA over UDP.
Build a stationA dongle, an antenna and the Quick Start.

Alternative hardware

Truly plug and play: the dAISy-catcher.

Any common SDR will do, and an RTL-SDR dongle of around €30 is all you need. If you would rather not tinker, there is the dAISy-catcher. Plug it in as a standard USB device, or stack it on a Raspberry Pi as a HAT: no driver to install and no experimenting with filters and amplifiers. The dAISy-catcher is designed to be a best-in-class AIS receiver, developed by Wegmatt in collaboration with AIS-catcher. It puts the RF front end, the radio and the decoding in one compact, powerful device.

The dAISy-catcher at Wegmatt ↗

Jasper

Who is behind it

I'm Jasper.

I started AIS-catcher in 2021 because my own reception was poor. There was only so much I could do about the antenna, and I noticed that the software made a surprisingly big difference — so that is where I kept digging. It is a hobby project: no company, no paywall, GPL v3, and the code has been on GitHub from the first commit. Getting the most out of each and every station is the passion.

If you want to help, running a station that shares is the biggest thing. After that: bug reports, recordings of signals that decode badly, and pull requests. Most conversation happens in the GitHub discussions.

AIS-catcher only listens, never transmits. It is a research and educational tool and not for navigation or safety of life. Rules on receiving and republishing radio data vary by country.

Ready to put a station on the map?

A computer, a dongle and an antenna. The rest is on the next page.

Quick Start Add a station Documentation