Preamble (Intendend Application and Limitations on Use)

August 4, 2007

The NMEA 0183 standard is intendend to support one-way serial data transmission from a SINGLE TALKER to one or more LISTENERS. The data transmited is human readable because is in ASCII and the data includes information such as: position, speed, depth, frequency, allocation, altitude, course, etc… And the instruments which can “speak” in NMEA can be GPS, Weather, Sounder, Heading, Velocity, Randar and others. A typical message in ACII mode might be 11 to a maximum of 79 characters in length and generally require transmission no more often than once per 20 mili-seconds.

The eletronical definitions in this standard are intended to operate at 38.4K-baud, a higher data rate than 4800-baud NMEA 0183.

IMPORTANT: Since there is no provision of guaranteed delivery of messages and only limited error-checking capability, this standard should be used with caution in crtical applications.

Just to understand:

1 – TALKER: Is any device that sends data to other devices within NMEA standard. We can indentify the type of talker by the 2-character mnemonic.

Some of these 2-character mnemonic can be for example:

Heading Track Controller (Autopilot) General AG*
Magnetic AP
Automatic Indentification System AI
COMUNICATIONS: Digital Selective Calling (DSC) CD*
Data Receiver CR
Satellite CS*
Radio-Telephone (MF/HF) CT*
Radio-Telephone (VHF) CV*
Scanning Receiver CX*

DECCA Navigator DE
Direction Finder DF*
Eletronic Chart System (ECS) EC
Eletronic Chart Display & Information System (ECDIS) EI
Emergency Position Indicating Beacon (EPIRB) EP*
Engine room Monitoring Systems ER
GLONASS Receiver GL
Global Navigation Satellite System (GNSS) GN
Global Positioning System (GPS) GP
HEADING SENSORS: Compass, Magnetic HC*
Gyro, North Seeking HE*
Gyro, Non-North Seeking HN

Integrated Instrumetation II
Integrated Navigation IN
Loran C LC
Propietary Code P
Radar and/or Radar Plotting RA*
Sounder, depth SD*
Eletronic Positioning System, other/general SN
Sounder, scanning SS
Turn Rater Indicator TI*
VELOCITY SENSORS: Doppler, onther/general VD*
Speed Log, Water, Magnetic VM
Speed Log, Water, Mechanical VW
Voyage Data Recorder VR
Transducer YX
TIMEKEEPERS, TIME/DATE: Atomic Clock ZA
Chronometer ZC
Quartz ZQ
Radio Update ZV
Weather Instruments WI

*Designated by IEC for use with IMO maritime eletronic devices. This is the minimum requirement for equipment that is required by IMO in the SOLAS Convention (1974, as amended).

2 – LISTENER: is any device that receives data from another device within the NMEA standard.

Thats it, for now.
References:

Nmea Publications, NMEA 0183-HS 38.4 K Baud Serial Data Standard For Interfacing Marine Eletronic Devices, Version 1.01, November 1, 2002

Nmea 0183 Standard For Interfacing Marine Eletronics Devices, Version 3.01, January 1, 2002

What is NMEA?

August 3, 2007

According to NMEA website www.nmea.org : “The National Marine Electronics Association (NMEA) is the unifying force behind the entire marine electronics industry, bringing together all aspects of the industry for the betterment of all in our business“. We can take a close look in the following sentence “unifying force behind the entire marine eletronics industry“, yeah is a standard.

The aim of NMEA standard is to facilitate the interconnection and interchangeability between different equipments minimizing misunderstanding and confusion between manufactures and assisting purchasers in selecting compatible equipment.

If I have an antenna or a receiver which respects the NMEA standard protocol, is possible send information from it to Radar or Sounder or any other stuff that can understand NMEA protocol.

Nowadays some applications largely used is to take a GPS which transmits the information by NMEA protocol and develop programs that interpret all the information from GPS and do many richest stuffs. Like showing the position in a web map, do a tracker or any other stuff really interesting and useful.

I will show here a lot of things about NMEA, because is not so easy find this kind of information on internet. We can find on internet some tables/schemes showing what is some kind of protocol but any other information besides it. I will put here too, some parts of NMEA publications because these publications is really expensive. (But I won’t put the entire publications because I should respect copyright laws, but some citation, examples, parts and references I will put 😉 ). I want do this to help the people who hasn’t enough money to buy the documents.

Well I think that for my first article is ok. I’m accepting feedback too correct some wrong information that I wrote or some advice.

Thats it. Seeya!

References

www.nmea.org

Nmea Publications, NMEA 0183 Standard for Interfacing Marine Eletronic Devices, Version 3.01, January 1, 2002.