NMEA0183

NMEA 0183 is a marine serial communications standard. It defines a format for the transmission of GPS information, speed and course data, and other navigation data between navigation devices and other electronic devices on boats.

Benefits of NMEA 0183:

• Common: NMEA 0183 is a common standard supported by many legacy devices
• Ease of implementation: It is easy to develop a device for NMEA 0183 as there are simple protocols and a well-documented specification. The data is transmitted in ASCII and is easy to read, so that the functionality can be checked without much effort.
• Compatibility: Devices that support NMEA 0183 can communicate with each other, making it easier to integrate systems and share information.
• Expandability and openness: The NMEA0183 protocol can be expanded with your own data sets and does not require certification of the implementation. Any data sets can be integrated into NMEA0183 via XDR-Sentences.
• Simple implementation: Due to the low data rate, simple two-wire wiring systems can be used, which makes implementation easier. In addition, no special expensive connector systems are used and can be implemented with simple screw terminals.
• Long cables: The cable lengths can be up to 1000 m.

Disadvantages of NMEA 0183:

• Legacy Technology: NMEA 0183 is an older protocol and may be overtaken by more modern technologies such as NMEA 2000 or NMEA OneNet.
• Limited Data Capacity: NMEA 0183 has a limited capacity for transmitting data, especially when compared to more modern protocols. The standard initially only provided for speeds of 4800 Bd, but was gradually increased to 115200 Bd for some special applications.
• Connectivity: NMEA0183 is a point-to-point serial communication protocol. A data transmitter is always connected to one or more data receivers. Communication is always unidirectional. It cannot be sent and received at the same time.
• Bus systems: NMEA0183 can be implemented in various ways as a bus system (RS232, RS422, RS485, RS232-TTL). The multitude of possibilities increases the complexity when connecting to other systems. It is often not clear which implementation is involved. Resulting connection errors that are difficult to detect and fix.
• Data Security: NMEA 0183 does not have fault-tolerant security functionality, making it more vulnerable to data loss. Although the telegrams are provided with a checksum and errors can be detected, a faulty transmission cannot be resent.

Overall, NMEA 0183 is a useful standard for transmitting navigational data on boats, but it has limitations and cannot compete with more modern technologies in all applications. In order to be able to combine data from several data sources such as sensors into one data stream, there are so-called multiplexer.

Fig.: NMEA0183 gateway with WiFi converter (ship module)

The multiplexer receives various data telegrams at different ports and outputs the combined data stream from several sensors at a new data port. In this way, several sensor signals can be transmitted via a cable to a data terminal device such as a plotter or multifunction display. Many multiplexers also offer the option of separating certain data telegrams in the data stream with a filter function to suppress. For example, only the data that is really necessary can be transmitted to an autopilot, or ambiguities caused by multiple GPS receivers can be avoided.

Due to the simplicity of the NMEA0183 protocol, it can also be sent via TCP/IP or UDP telegrams and can therefore be used in LAN or WiFi networks. This compensates for some disadvantages such as the low data capacity and data security and NMEA0183 thus closes to more modern transmission technologies. Among other things, NMEA0183 via TCP/IP or UDP has established itself as the quasi-standard for data connections with third-party software.