Signal K is the next generation solution for marine data exchange. It not only allows for communication between instruments and sensors on board a single vessel, but also allows sharing of data between multiple boats, aids to navigation, bridges, marinas and other land-based resources. It is designed to be easily used by Web and Mobile applications and to connect modern boats to the Internet of Things.


In the last few years, it has become clear that there is a real need for a new communications protocol for the marine industry that will address the needs of a changing and ever more interconnected world. There are a number of existing marine data protocols, some that are proprietary such as Raymarine’s SeaTalk interface, but the two most popular were both developed by the National Marine Electronics Association (the NMEA):-

NMEA 0183

Based on the RS422 serial interface, is now over 35 years old but has aged remarkably well and is still in use on many leisure and commercial vessels. As you can see from the diagram, you have to have lots of pairs of wires going between equipment, in fact two pairs of wires if you want bi-directional communication. It is primarily a one to one method of communication although you can have 3 or 4 “listeners” (inputs) connected to one “talker” (output).

Typical NMEA 0183 Implementation

NMEA 2000

Based on the same CAN Bus technology used in cars, is now over 15 years old and although adoption was relatively slow, most new boats have an NMEA 2000 network. It can handle a wide spread of information sources from engines to stereos and is faster that NMEA0183 but more difficult to interface to.

As you can see from the diagram, you have a network “back bone” with “spurs” or drop cables that take power and data to the equipment. Every device on the network can talk or listen to any other device or broadcast to all devices.

Typical NMEA 2000 Implementation

For developers of modern mobile/web apps and cloud services, there are two main problems with the existing standards.


Both standards are fundamentally local area serial networks designed for limited deployments in simple environments. NMEA 0183 is normally limited to 4800 baud (or 34,800bps in high speed mode) and one transmitting device. NMEA 2000 works at a significantly higher bit-rate (250kbps) and allows multiple devices to transmit on one shared bus, but it is limited to 50 devices on a bus. These decisions may have been perfectly rational twenty or thirty years ago, but today we need something more capable and extensible.

Although all NMEA standards are published and available for use by any developer and therefore are technically “open standards”, anyone wishing to use them must not only pay for the standards but also sign a license agreement which restricts how they can be used and in the case of NMEA 2000, a non-disclosure agreement. Hardware manufacturers are also obliged to have their equipment ‘certified’ before they can sell it, an expensive process for small companies. In essence, this prevents the release of an open source application developed using these standards and presents a high cost of entry for smaller developers.

Technical and Legal Barriers

Finally, and most importantly, both NMEA standards and the other proprietary protocols in the industry were developed when the instruments on the average boat were much simpler and much less capable. In a world where your home thermostat is connected to the Internet and the number of worldwide Internet connected devices is projected to exceed 30 billion by 2020, it seems archaic that your boat is still an island to itself.

After all, there are lots of other boats out there, and lots of other sources of information, all of which could be of interest and benefit to you. In the modern connected world, shouldn’t you be able to access that information from your boat where ever you are and on whatever device you want?

To move forward we need to think in a connected way, a way fundamentally different from NMEA protocols. Sun Microsystems famously coined the phrase The network is the computer, and Signal K reflects that global peer-to-peer concept.

The Internet of Things

The ability to share information with other boats, and via the Internet, has the potential to revolutionise the way nautical data is treated both afloat and ashore. Applications will be limited only by developers’ imagination, but could include:

  • Innovative Apps: If a standard is free to use, cost of entry is lower. This is encouraging new software and hardware developers to compete on providing new solutions.
  • Crowd-Sourced data: Aircraft already share information on clear-air turbulence, similarly, boats could share real-time information on weather with each other.
  • Boat Monitoring: It becomes simple to monitor the health of your boat, onboard or afloat, wherever you are in the world.
  • Fleet Management: Flotilla companies could monitor their fleet to get advance notice of problems occurring.
  • Marinas: It should be possible to book marina berths direct from your Chartplotter. By sharing your information with the Marina, they get real-time information on your arrival.
  • Race Management: The monitoring and management of Race Fleets, currently the province of major round-the-world events, can be brought to club level.
  • Pilotage & Cruising Information: Real time information from established organisations can be beamed directly to your boat to enhance your onboard tools.


We are constantly hearing horror stories of the latest security flaw being exploited by hackers and it is extremely important that any modern data standard, that allows your information to be transferred across the Internet, has security designed in to its heart.

The Internet has widely adopted and proven security standards, so there was no need to reinvent the wheel. Signal K supports secure, encrypted HTTPS and WSS connections, with the same authorisation and authentication techniques that you are using everyday on Facebook, Paypal, Googlemail, online banking, etc.

As a user, having fun sailing miles out at sea, it is easy to forget about security, but the in-built security of Signal K coupled with your own good security practices like strong passwords and WPA2 encryption on your wireless router, will keep your data safe.

Signal K

Signal K uses modern techniques to create a marine data standard for the 21st Century. It is:

  • Open. It is free for anyone to use. Signal K is managed by a community of boaters, and developers are able to propose improvements to the standard.
  • Modern. It uses widely available, Open Source technologies.
  • Extensible. It can mature with new requirements as they emerge.
  • Flexible. Signal K is not tied to specific hardware
  • Respectful. It is designed to interface to existing equipment and protocols.

It is easy to get started with Signal K. With a Google Group for users, Slack Channels for developers, lots of online information, low cost hardware and many free or low costs apps and solutions, you can quickly build a system and start benefiting from the tens of thousands of man-hours of community development that has gone in to Signal K.

Signal K works by having a small black box—a Signal K Server—on board your boat. This can interface to existing NMEA networks onboard as well as databases, other Signal K data streams, and potentially land-based and cloud-based resources. The server can also hold static items like charts, routes and notes. It can also hold and act as a web-server for browser-based Apps.

The Signal K server is available as a ready-to-fit commercial product (such as the Digital Yacht iKommunicate), or you can download the software for free and run it yourself. The software runs on a range of single board computers as well as Linux, Windows and MacOS, see the Install page for details.

One of the latest developments on the Signal K Node server, is the support for Plugins. A plugin is an extra software component (program) that adds a specific feature to an existing computer program, in this case the Node Server. There are an increasing number of plugins being released and they are easily selected and installed on the “Signal K Plugin Store”.

List of Available “Plugins”

A list of all the latest Signal K Apps and Services can be found on the Applications and Solutions page.

Signal K is an on-going, collaborative effort between a global network of volunteers and interested hardware manufacturers and software vendors in the marine industry. We encourage you to get in touch via the mailing list or group chat in our Slack channel. Suggestions and requests via Github are also welcome.