NMEA OneNet is the National Marine Electronics Association’s most recent standard, one of only three major electronics standards the organization has released in the past 40-plus years. First came NMEA 0183 in 1983, then NMEA 2000 in 2001, and now OneNet. The previous standards stood the test of time. In fact, despite being 41 years old, NMEA 0183 continues to be built into many electronics and remains the preferred standard for many light commercial vessels.

NMEA 2000 delivered on the NMEA’s promise of a single network carrying critical navigation data such as position, depth and environmental conditions. In the 23 years since its introduction, NMEA 2000 has gained tremendous adoption and been extended to carry even more data. Today, an NMEA 2000 network might carry navigation information, engine gauge data, nearby AIS targets, digital switching status and control messages, and enable control of a boat’s climate-control systems.

Why a New Standard?

NMEA 2000 advanced interoperability and integration of electronics, but it’s also starting to show its limits. An NMEA 2000 network supports a maximum of 50 physical devices. However, network performance can begin to degrade before the 50-device limit is hit. When NMEA 2000 was being developed, 50 devices seemed sublime. Today, it’s easy to envision very large networks.

NMEA 2000 introduced the electronics world to controller area network (CAN bus) as a means of transferring information all over the boat. This standard, developed for automotive networks, transfers relatively limited information over the network. With 250 kilobits per second of throughput, it’s appropriate for numeric data and some text, such as AIS messages with vessel information. But NMEA 2000 can’t support higher-bandwidth services such as radar, graphical sonar displays and video.

And it has become clear that security must also be considered. The networks that run our boats, cars and houses must be robust and resistant to uninvited access. NMEA 2000’s only security comes from physical access. So if you can physically access the network, you can access all the information on it.

OneNet: The New Standard

NMEA’s OneNet appears to deliver on today’s needs while being designed to age well. Based on Ethernet, OneNet addresses the scalability and throughput limitations of NMEA 2000, and lays a secure framework to ensure safety and security.

OneNet operates on Ethernet networks ranging from 100 megabits per second to 10 gigabits per second. That’s 400 to 40,000 times faster than NMEA 2000. Utilizing TCP/IP’s IPv6 for IP addressing effectively removes any limit on the number of devices.

An NMEA 2000 network is limited to 3 amps at 12 volts or 36 watts. OneNet utilizes the power-over-ethernet standard to support up to 25.5 watts to each device on the network. OneNet also defines security standards for the entire network. The details are complex, but physically accessing the network simply won’t be enough to gain access to it and the information it carries. Devices will need to be admitted to the network before they can participate.

When NMEA 2000 replaced 0183, there wasn’t a migration path or compatibility. OneNet takes a different approach.
This network is designed with the concept of built-in gateways. Those gateways allow interoperability with NMEA 2000 or 0183, and allow data from those networks to be transported over the OneNet network.

Because of its vastly improved bandwidth, power delivery and network size, OneNet can carry much more and many more types of data. Where NMEA 2000 is limited to numerical and textual data, OneNet can carry the most graphically intensive data available on a boat.

The data carried, in addition to the familiar workloads from NMEA 2000, include radar, sonar, video and nearly anything else developers can dream up. Plus, by defining standard ways of exchanging information, OneNet can enable sharing sensor output across brands. So if two companies decide to develop and support it, a Raymarine screen might be able to display and control a Simrad radar.

It Won’t Happen Overnight

Rolling out and driving adoption of a new standard isn’t easy. OneNet’s road is likely to be a little more difficult than NMEA 2000’s. OneNet dictates specific connectors to meet the standard. In areas exposed to weather, an M12 X-coded connector must be used on the device. (Devices installed in enclosed environments can use a standard RJ45 connector.) Manufacturers that have been using proprietary connectors for a decade or more might be hesitant to make a switch. And to boat owners and operators, the promise of interoperability between brands may be enticing, but electronics manufacturers might not be as excited.

I think gateways from OneNet to NMEA 2000 and NMEA 0183 will be some of the first products we see. Larger NMEA 2000 systems can suffer performance problems. Today’s remedy is to separate networks into smaller segments, but segmenting networks limits what data is available on various displays. A gateway that allows sharing the data would be an improvement.

Today, many third-party integrations require separate development for each electronics manufacturer’s products. So for a stabilizer control system, lighting controller or night vision camera to be viewable on multifunction displays, separate development is required for each platform. That means if Seakeeper wants its users to be able to control gyros from a multifunction display, Seakeeper must go through the development effort for Garmin, Furuno, Raymarine and Navico. On the other hand, if each of the displays supports OneNet integrations, Seakeeper will only have to develop one app.

Long-Term Success

The new standard’s long-term success will ultimately come down to adoption. For OneNet to deliver on the promise of being one network for all the boat’s needs, individual components and systems on the boat need to implement it. As consumer awareness of OneNet increases, demand should help drive OneNet implementation throughout the market.

The NMEA is working on a program to encourage individual developers to embrace OneNet. That program will reduce the initial expense by making a development environment, certification tool and access to the standard available as a monthly subscription. Overall, the organization takes a long view as it develops and implements standards. It may take a while, but I think the entire industry stands to benefit from OneNet’s success. 

This article was originally published in the May 2024 issue.