NMEA 0183
From Wikipedia, the free encyclopedia
NMEA 0183 (or NMEA for short) is a combined electrical and data specification for communication between marine electronic devices such as depth finders, navigation instruments, and GPS receivers. It has been defined by, and is controlled by, the US based National Marine Electronics Association. It is also commonly used for GPS receivers other than on board boats.
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.
Contents |
[edit] Serial Configuration
Baud Rate: 4800 Data Bits: 8 Parity: None Stop Bits: 1 (or more)
[edit] Protocol Rules
- 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.
Example of sentence:
Waypoint Arrival Alarm
$GPAAM,A,A,0.10,N,WPTNME*43
Where:
AAM Arrival Alarm A Arrival circle entered A Perpendicular passed 0.10 Circle radius N Nautical miles WPTNME Waypoint name *43 Checksum data
A compound string from the NR203 GPS Receiver containing multiple messages. The actual messages decoded include…
- ZDA – Standard NMEA $..ZDA Time & Date message
- GLL – Standard NMEA $..GLL Geographic Position – Latitude/Longitude message
- NSV – NMEA message containing individual satellite information.
Typical ASCII String
$<CR><LF>
MRK,0<CR><LF>
ZDA,123336.8069,17,06,2001,13.0<CR><LF>
GLL,2924.11158,N,1211.07392,W, 75.97,M<CR><LF>
VTG,218.7,T,2.38,H,0.18,V<CR><LF>
SGD,-1.0,G,-1.0,M<CR><LF>
SYS,3T,9<CR><LF>
ZEV,0.28745E-006<CR><LF>
NSV,2,00,000,00,0.0,00.0,00,00,D<CR><LF>
NSV,7,00,000,00,0.0,00.0,00,00,D<CR><LF>
NSV,28,00,000,00,0.0,00.0,00,00,N<CR><LF>
NSV,1,00,000,00,0.0,00.0,00,00,D<CR><LF>
NSV,13,00,000,00,0.0,00.0,00,00,D<CR><LF>
NSV,4,00,000,00,0.0,00.0,00,00,N<CR><LF>
NSV,25,00,000,00,0.0,00.0,00,00,N<CR><LF>
NSV,0,00,000,00,0.0,00.0,00,00,N<CR><LF>
NSV,11,00,000,00,0.0,00.0,00,00,D<CR><LF>
NSV,0,00,000,00,0.0,00.0,00,00,N<CR><LF>
&
| Description | Form | Field |
|---|---|---|
| Start Chars | "$" | 0 |
| UTC of position fix | ZDA,hhmmss.ssss,dd,mm,yyyy | 1 |
| Latitude | llll.lllll | 2 |
| Direction of Lat | (N or S) | 3 |
| Longitude | yyyy.yyyyy | 4 |
| Direction of Lon | (E or W) | 5 |
| Number of SVs | NSV | 6 |
| Sat. i.d. number | NSV,n,… | 7 |
| Repeated for “n” sats | ||
| End Character | “&” |
The new standard, NMEA 2000, accommodates several "talkers" at a higher baud rate, without using a central hub.
The NMEA standard is proprietary and sells for at least US$ 270 as of March 2007. [1] However, much of it has been reverse-engineered from public sources and is available in references like gpsd, Glenn Baddeley's and Dale DePriest's.
[edit] Vendor extensions
Most GPS manufacturers include special messages to the standard NMEA set in their products for maintenance and diagnostics purposes. These extended messages are not standardized at all and are normally different from vendor to vendor.
