Contents:

1. What is NMEA?
   1. What is an NMEA Standard
   2. NMEA Address
2. Electrical Interface
3. NMEA-0180 and NMEA-0182
   1. Simple Format
   2. Complex Format
4. NMEA-0183
   1. General Sentence Format
   2. Sentences sent by specific equipment
   3. Sample Sentences Dissected
      1. Standard Sentences
      2. Proprietary Sentences
5. RS-232 Connections
6. Troubleshooting
7. About the Author
   1. Acknowledgements

1. What is NMEA?

The National Marine Electronics Association (NMEA) is dedicated to the education and advancement of the marine electronics industry. 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”)

1.1 What is an NMEA Standard?

An NMEA standard defines an electrical interface and data protocol for communications between marine instrumentation (they may also have standards for other things).

1.2 NMEA Address

Address: NMEA 7 Riggs Avenue Severna Park, MD 21146 Beth Kahr, President Phone: 410-975-9425 Email: director@nmea.org Website: www.nmea.org

2. Electrical Interface

These standards allow a single “talker”, and several “listeners” on one circuit. The recommended interconnect wiring is a shielded twisted pair, with the shield grounded only at the talker. The standards do not specify the use of any particular connector.

3. NMEA-0180 and NMEA-0182

3.1 Simple Format

The simple format consists of a single data byte transmitted at intervals of 0.8 to 5 seconds, at 1200 baud with odd parity.

3.2 Complex Format

The complex format consists of a data block of 37 bytes of mostly readable ASCII text, giving cross-track error, bearing to waypoint, present Lat/Long, and a binary status byte.

4. NMEA-0183

4.1 General Sentence Format

Under the NMEA-0183 standard, all characters used are printable ASCII text (plus carriage return and line feed). Data is transmitted in the form of “sentences”, starting with “$”, followed by a two-letter talker ID, a three-letter sentence ID, and terminated by an optional checksum.

4.2 Sentences Sent by Specific Equipment

This section lists the sentence types used by various equipment. The format and data included in each sentence type are given in section 4.3.

4.3 Sample Sentences Dissected

4.3.1 Standard Sentences

Here are some common sentences:

• APB: Autopilot Format B
• BOD: Bearing – Origin to Destination Waypoint
• BWC: Bearing and Distance to Waypoint
• DBT: Depth Below Transducer
• GGA: Global Positioning System Fix Data
• GLL: Geographic Position, Latitude and Longitude
• GSA: GPS DOP and Active Satellites
• GSV: Satellites in View

4.3.2 Proprietary Sentences

These are specific to manufacturers. For example:

• $PGRME,15.0,M,45.0,M,25.0,M*22
• $PGRMZ,93,f,3*21

5. RS-232 Connections

RS-232 standard defines two classes of devices that can communicate using serial data – Data Terminal Equipment (DTE) and Data Communication Equipment (DCE). If you are connecting a GPS to a computer, you may need to know about RS-232 serial ports.

6. Troubleshooting

– Check if the talker (GPS or Loran) can send NMEA-0183. – Verify that the listener understands NMEA-0183 and the sentences it sends.

7. About the Author

This section gives information about the author of the FAQ.

7.1 Acknowledgements

Credits to the contributors of this document.