NMEA 0183 is a combined electrical and data specification for communication between marine electronics such as echo sounder, sonars, anemometer, gyrocompass, autopilot, GPS receivers and many other types of instruments. It has been defined and is controlled by the National Marine Electronics Association (NMEA). It replaces the earlier NMEA 0180 and NMEA 0182 standards. [1] In leisure marine applications, it is slowly being phased out in favor of the newer NMEA 2000 standard, [2] [3] though NMEA 0183 remains the norm in commercial shipping.
The electrical standard that is used is EIA-422, also known as RS-422, although most hardware with NMEA-0183 outputs are also able to drive a single EIA-232 port. The standard calls for optically isolated inputs. There is no requirement for isolation for the outputs.
The NMEA 0183 standard uses a simple ASCII, serial communications protocol that defines how data are transmitted in a "sentence" from one "talker" to multiple "listeners" at a time. Through the use of intermediate expanders, a talker can have a unidirectional conversation with a nearly unlimited number of listeners, and using multiplexers, multiple sensors can talk to a single computer port.
At the application layer, the standard also defines the contents of each sentence (message) type, so that all listeners can parse messages accurately.
While NMEA 0183 only defines an RS-422 transport, there also exists a de facto standard in which the sentences from NMEA 0183 are placed in UDP datagrams (one sentence per packet) and sent over an IP network.
The NMEA standard is proprietary and sells for at least US$2000 (except for members of the NMEA) as of September 2020. [4] [5] However, much of it has been reverse-engineered from public sources. [6] [7]
Typical Baud rate | 4800 |
Data bits | 8 |
Parity | None |
Stop bits | 1 |
Handshake | None |
There is a variation of the standard called NMEA-0183HS that specifies a baud rate of 38,400. This is in general use by AIS devices.
ASCII | Hex | Dec | Use |
---|---|---|---|
<CR> | 0x0d | 13 | Carriage return |
<LF> | 0x0a | 10 | Line feed, end delimiter |
! | 0x21 | 33 | Start of encapsulation sentence delimiter |
$ | 0x24 | 36 | Start delimiter |
* | 0x2a | 42 | Checksum delimiter |
, | 0x2c | 44 | Field delimiter |
\ | 0x5c | 92 | TAG block delimiter |
^ | 0x5e | 94 | Code delimiter for HEX representation of ISO/IEC 8859-1 (ASCII) characters |
~ | 0x7e | 126 | Reserved |
<CR><LF>
ends the message.As an example, a waypoint arrival alarm has the form:
Another example for AIS messages is:
The main talker ID includes: [8] [9]
NMEA message mainly include the following "sentences" in the NMEA message: [10]
Sentence | Description |
---|---|
$Talker ID+GGA | Global Positioning System Fixed Data |
$Talker ID+GLL | Geographic Position—Latitude and Longitude |
$Talker ID+GSA | GNSS DOP and active satellites |
$Talker ID+GSV | GNSS satellites in view |
$Talker ID+RMC | Recommended minimum specific GPS data |
$Talker ID+VTG | Course over ground and ground speed |
One example, the sentence for Global Positioning System Fixed Data for GPS should be "$GPGGA".
Most GPS manufacturers include special messages in addition to the standard NMEA set in their products for maintenance and diagnostics purposes. Extended messages begin with "$P". These extended messages are not standardized.
NMEA 0183 is supported by various navigation and mapping software. Notable applications include:
nmea(4)
pseudo-device driver [12] A sample file produced by a Tripmate 850 GPS logger. This file was produced in Leixlip, County Kildare, Ireland. The record lasts two seconds.
$GPGGA,092750.000,5321.6802,N,00630.3372,W,1,8,1.03,61.7,M,55.2,M,,*76 $GPGSA,A,3,10,07,05,02,29,04,08,13,,,,,1.72,1.03,1.38*0A $GPGSV,3,1,11,10,63,137,17,07,61,098,15,05,59,290,20,08,54,157,30*70 $GPGSV,3,2,11,02,39,223,19,13,28,070,17,26,23,252,,04,14,186,14*79 $GPGSV,3,3,11,29,09,301,24,16,09,020,,36,,,*76 $GPRMC,092750.000,A,5321.6802,N,00630.3372,W,0.02,31.66,280511,,,A*43 $GPGGA,092751.000,5321.6802,N,00630.3371,W,1,8,1.03,61.7,M,55.3,M,,*75 $GPGSA,A,3,10,07,05,02,29,04,08,13,,,,,1.72,1.03,1.38*0A $GPGSV,3,1,11,10,63,137,17,07,61,098,15,05,59,290,20,08,54,157,30*70 $GPGSV,3,2,11,02,39,223,16,13,28,070,17,26,23,252,,04,14,186,15*77 $GPGSV,3,3,11,29,09,301,24,16,09,020,,36,,,*76 $GPRMC,092751.000,A,5321.6802,N,00630.3371,W,0.06,31.66,280511,,,A*45
Note some blank fields, for example:
NMEA 0183 continued to be maintained separately: V4.10 was published in early May 2012, and an erratum noted on 12 May 2012. [15] On November 27, 2018, it was issued an update to version 4.11, which supports Global Navigation Satellite Systems other than GPS. [16]
The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radio navigation system owned by the United States Space Force and operated by Mission Delta 31. It is one of the global navigation satellite systems (GNSS) that provide geolocation and time information to a GPS receiver anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites. It does not require the user to transmit any data, and operates independently of any telephone or Internet reception, though these technologies can enhance the usefulness of the GPS positioning information. It provides critical positioning capabilities to military, civil, and commercial users around the world. Although the United States government created, controls, and maintains the GPS system, it is freely accessible to anyone with a GPS receiver.
8-bit clean is an attribute of computer systems, communication channels, and other devices and software, that process 8-bit character encodings without treating any byte as an in-band control code.
In the context of information security, and especially network security, a spoofing attack is a situation in which a person or program successfully identifies as another by falsifying data, to gain an illegitimate advantage.
Modbus or MODBUS is a client/server data communications protocol in the application layer. It was originally designed for use with programmable logic controllers (PLCs), but has become a de facto standard communication protocol for communication between industrial electronic devices in a wide range of buses and networks.
GPS Exchange Format (GPX) is an XML schema designed as a common GPS data format for software applications. It can be used to describe waypoints, tracks, and routes. It is an open format and can be used without the need to pay license fees. Location data is stored in tags and can be interchanged between GPS devices and software. Common software applications for the data include viewing tracks projected onto various map sources, annotating maps, and geotagging photographs based on the time they were taken.
The Financial Information eXchange (FIX) protocol is an electronic communications protocol initiated in 1992 for international real-time exchange of information related to securities transactions and markets. With trillions of dollars traded annually on the NASDAQ alone, financial service entities are employing direct market access (DMA) to increase their speed to financial markets. Managing the delivery of trading applications and keeping latency low increasingly requires an understanding of the FIX protocol.
An automotive navigation system is part of the automobile controls or a third party add-on used to find direction in an automobile. It typically uses a satellite navigation device to get its position data which is then correlated to a position on a road. When directions are needed routing can be calculated. On the fly traffic information can be used to adjust the route.
The automatic identification system (AIS) is an automatic tracking system that uses transceivers on ships and is used by vessel traffic services (VTS). When satellites are used to receive AIS signatures, the term Satellite-AIS (S-AIS) is used. AIS information supplements marine radar, which continues to be the primary method of collision avoidance for water transport. Although technically and operationally distinct, the ADS-B system is analogous to AIS and performs a similar function for aircraft.
Intel hexadecimal object file format, Intel hex format or Intellec Hex is a file format that conveys binary information in ASCII text form, making it possible to store on non-binary media such as paper tape, punch cards, etc., to display on text terminals or be printed on line-oriented printers. The format is commonly used for programming microcontrollers, EPROMs, and other types of programmable logic devices and hardware emulators. In a typical application, a compiler or assembler converts a program's source code to machine code and outputs it into a object or executable file in hexadecimal format. In some applications, the Intel hex format is also used as a container format holding packets of stream data. Common file extensions used for the resulting files are .HEX or .H86. The HEX file is then read by a programmer to write the machine code into a PROM or is transferred to the target system for loading and execution. There are various tools to convert files between hexadecimal and binary format, and vice versa.
The Simple Sensor Interface (SSI) protocol is a simple communications protocol designed for data transfer between computers or user terminals and smart sensors.
The Radio Technical Commission for Maritime Services (RTCM) is a non-profit international standards organization. Although started in 1947 as a U.S. government advisory committee, RTCM is now an independent organization supported by its member organizations from all over the world.
Raymarine is a manufacturer and major supplier of electronic equipment for marine use. The company targets both recreational and light commercial markets with their products, which include:
The National Marine Electronics Association (NMEA) is a US-based marine electronics trade organization setting standards of communication between marine electronics.
NMEA 2000, abbreviated to NMEA2k or N2K and standardized as IEC 61162-3, is a plug-and-play communications standard used for connecting marine sensors and display units within ships and boats. Communication runs at 250 kilobits-per-second and allows any sensor to talk to any display unit or other device compatible with NMEA 2000 protocols.
In the field of geodesy, Receiver Independent Exchange Format (RINEX) is a data interchange format for raw satellite navigation system data. This allows the user to post-process the received data to produce a more accurate result — usually with other data unknown to the original receiver, such as better models of the atmospheric conditions at time of measurement.
Marine electronics refers to electronics devices designed and classed for use in the marine environment on board ships and yachts where even a small amount of salt water can destroy some electronics devices. Therefore, the majority of these types of devices are either water resistant or waterproof.
In data networking, telecommunications, and computer buses, an acknowledgement (ACK) is a signal that is passed between communicating processes, computers, or devices to signify acknowledgment, or receipt of message, as part of a communications protocol. Correspondingly a negative-acknowledgement is a signal that is sent to reject a previously received message or to indicate some kind of error. Acknowledgments and negative acknowledgments inform a sender of the receiver's state so that it can adjust its own state accordingly.
IEC 61162 is a collection of IEC standards for "Digital interfaces for navigational equipment within a ship".
Time synchronization in North America can be achieved with many different methods, some of which require only a telephone, while others require expensive, sensitive, and rare electronic equipment. In the United States, the United States Naval Observatory provides the standard of time, called UTC(USNO), for the United States military and the Global Positioning System, while the National Institute of Standards and Technology provides the standard of time for civil purposes in the United States, called UTC(NIST).
RTCM SC-104 is a communication protocol for sending differential GPS (DGPS) to a GPS receiver from a secondary source like a radio receiver. The standard is named for the Special Committee 104 of the Radio Technical Commission for Maritime Services (RTCM) that created it. The format does not define the source of the messages and has been used with systems as varied as longwave marine radio, communications satellite broadcasts, and internet distribution.