How onboard device data is used in the commercial marine sector

Navigating Onboard Data and NMEA 0183 in the Commercial Marine Sector

Introduction to commercial marine diversity

The commercial sector is vast, and ranges from smaller commercial craft and fishing boats, through to cargo ships and cruise liners. With such a variety of vessels, there is no ‘one size fits all’ solution when it comes to the collection and distribution of onboard instrument data. Different vessels require different equipment on board depending on their operational requirements, and installation methods can vary dramatically.

Installation challenges on commercial vessels

Unlike leisure craft, commercial vessels are often exposed to extreme weather and water conditions, making the installation location of power supplies, equipment, and safety gear require much more consideration. Excess vibration, impact from waves, water coming onboard, storms and high winds can all be very damaging to your electronics, so thoughtful planning and installation are required.

System complexity and vessel scale

On board systems are typically much larger, often with multiple sub-systems operating independently, or sometimes together. On the smaller end of the scale, with fishing vessels and workboats, these may all be on one system, with a common control area at the bridge or helm. However, when we get to the large end of the scale, various areas of the ships will have their own systems, and combining these can be challenging.

Why NMEA 0183 still thrives in the commercial sector

This is one of the reasons we see a lot of the commercial industry still using NMEA 0183 equipment. The cable length constraints of NMEA 2000 are too short for a cargo ship, and the 50 physical device limit can sometimes be problematic, too. As NMEA 0183 devices are all independent, and RS-422 will go up to 1000m, it’s much easier to collate all the individual devices’ data together using multiplexers (combiners) and buffers (splitters) than it is to try and make it work with NMEA 2000, converters and bridges.

NMEA: Buffers, splitters, combiners, multiplexers… What’s the difference?!
There is sometimes confusion over the terms used for the DCU (Data Control Units) used to collect and route NMEA data. In a nutshell, “buffers” and “splitters” are the same thing, feeding data from a small number of input devices (most often GPS) to inform a high number of output devices (AIS, gyro, autopilot, etc…).

Similarly, “combiners” and “multiplexers” are the same thing, doing the converse to buffers/splitters. They will collect multiple feeds of data from a high number of input devices, and output to a smaller number of output devices (ECDIS, onboard PC systems, etc…)

Specialist systems and installation hurdles

The type of vessel will also dictate any specialist equipment or systems required. For example, a fishing vessel will operate with transducers and fish finders along with other mapping equipment to plot fish density, water temperature, etc., whilst a large cargo ship or something which falls under the SOLAS bracket may require space for one or multiple ECDIS on board.

However, NMEA 0183 systems do come with their challenges and headaches. Whilst it can be a benefit where every device is connected individually, and does add a level of redundancy, it also means a lot more wiring and careful installation are needed. Unlike NMEA 2000, where devices are powered from the bus, every piece of NMEA 0183 equipment needs its own power supply connection.

Cost comparisons and system trade-offs

On a ship where you may have 30 instruments, that’s a lot of wiring to supply points. Combine that with all of the wiring required for data inputs and outputs on devices, and you can quite easily end up with a bit of a rat’s nest of wires. This can be largely avoided by routing wiring in ducting and jackets, and labelling everything accordingly, but it doesn’t overcome the issue of the amount of actual wiring that’s needed.

In certain scenarios and installations, using a multitude of NMEA 0183 equipment can be more expensive than NMEA 2000 as well. When NMEA 0183 devices need to be connected and buffers/multiplexers are required, the cost can increase relatively quickly, depending on how much extra equipment you need to make it all work. Compare this with NMEA 2000, where everything operates on one bus and there’s no need for multiplexers, etc., and we can see why NMEA 2000 can quite often be a cheaper solution.

In summary…

Commercial vessels rely on a broad mix of technologies to handle onboard data, and there is no one-size-fits-all approach. NMEA 0183 continues to serve many installations well due to its flexibility, but can become complex and costly when scaling up. NMEA 2000 offers simpler integration and can reduce costs in many scenarios. Knowing the strengths and limitations of each is essential to making informed decisions for commercial marine operations.