What is NMEA?

The National Marine Electronics Association is dedicated to the education and advancement of the marine electronics industry and the market which it serves.

It is a non-profit association composed of manufacturers, distributors, dealers, educational institutions, and others interested in peripheral marine electronics occupations (quoted from a promo in "NMEA News")

What is an NMEA standard?

For the purposes of this article, an NMEA standard defines an electrical interface and data protocol for communications between marine instrumentation. (They may also have standards for other things.)

More about NMEA?

NMEA 0183 (or NMEA for short) is a combined electrical and data specification for communication between marine electronics and also, more generally, GPS receivers.

The NMEA 0183 protocol is a means by which marine instruments and also most GPS receivers can communicate with each other. It has been defined by, and is controlled by, the US based National Marine Electronics Association.

The NMEA 0183 standard uses a simple ASCII, serial communications protocol that defines how data is transmitted in a "sentence" from one "talker" to one or more "listeners". The standard also defines the contents of each sentence (message) type so that all listeners can parse messages accurately:

• Each message starting character is a dollar sign.
• The next first five characters identify the type of message.
• All data fields that follow are comma-delimited.
• The first character that immediately follows the last data field character is an asterisk.
• The asterisk is immediately followed by a two-digit checksum.

NMEA is a standard protocol, use by GPS receivers to transmit data. NMEA output is EIA-422A but for most purposes you can consider it RS-232 compatible. Use 4800 bps, 8 data bits, no parity and one stop bit (8N1). NMEA 0183 sentences are all ASCII. Each sentence begins with a dollar sign ($) and ends with a carriage return linefeed (). Data is comma delimited. All commas must be included as they act as markers. Some GPS do not send some of the fields. A checksum is optionally added (in a few cases it is manatory). Following the $ is the address field aaccc. aa is the device id. GP is used to identify GPS data. Transmission of the device ID is usually optional. ccc is the sentence formatter, otherwise known as the sentence name.