NMEA-0183 Data for DSC Radio
Posted: Tue Dec 11, 2018 12:06 pm
Most digital selective calling (DSC) VHF Marine Band radios are interfaced using NMEA-0183 to a source of digital data that provides automatic position updates. There are several NMEA-0183 sentences that can be used to send data to the radio. This article discusses the content of those sentences and which is most useful.
GGA—Fix Information
The GGA sentence will contain the following data:
Not every GPS receiver will send all fields of GGA. A typical receiver might send only TIme, Latitude, Longitude, Altitude, HDOP, and number of satellites in view. The GGA sentence is very useful for a radio DSC position fix update.
GGA—Fix Information
The GGA sentence will contain the following data:
- Time (UTC)
- Latitude
- N or S (North or South)
- Longitude
- E or W (East or West)
- GPS Quality Indicator
- 0 - fix not available,
- 1 - GPS fix,
- 2 - Differential GPS fix
- 0 - fix not available,
- Number of satellites in view, 00 - 12
- Horizontal Dilution of precision
- Antenna Altitude above/below mean-sea-level (geoid)
- Units of antenna altitude, meters
- Geoidal separation, the difference between the WGS-84 earth ellipsoid and mean-sea-level (geoid), "-" means mean-sea-level below ellipsoid
- Units of geoidal separation, meters
- Age of differential GPS data, time in seconds since last SC104 type 1 or 9 update, null field when DGPS is not used
- Differential reference station ID, 0000-1023
- Checksum
Not every GPS receiver will send all fields of GGA. A typical receiver might send only TIme, Latitude, Longitude, Altitude, HDOP, and number of satellites in view. The GGA sentence is very useful for a radio DSC position fix update.