NMEA 0183 sentences
Esri mobile GIS software supports a number of protocols for communicating with receivers, the most common of which is the NMEA 0183 version 2.0 standard protocol defined by the National Marine Electronics Association. The NMEA 0183 standard definition is available from http://www.nmea.org.
The NMEA 0183 standard defines sentences that are used to transmit data. These sentences consist of printable ASCII text (plus carriage return and line feed). Each sentence consists of the following data sequence:
- A $ always starts an NMEA 0183 sentence.
- A two-letter talker ID—for example, GP for global positioning system (GPS) receiver, GN is for global navigation satellite combined system (GNSS), and GL is for the global navigation satellite system (GLONASS)
- A three-letter sentence ID—for example, GGA.
- Several data fields separated by commas.
- An optional checksum to terminate the sentence and a carriage return or line feed.
The NMEA 0183 standard allows individual manufacturers to define proprietary sentence formats. These sentences start with $P, then a 3-letter manufacturer ID, followed by data from the manufacturer that follows the general format of the standard sentences.
A sample NMEA 0183 sentence for the GPS fix data might be as follows:
$GPGGA,121505,4807.038,N,01131.324,E,1,08,0.9,133.4,M,46.9,M, , *42
where
- $GPGGA is the NMEA 0183 sentence ID for the GPS fix data.
- 121505 is the fix taken at 12:15:05 UTC.
- 4807.038,N is latitude 48° 07.038' N.
- 01131.324,E is longitude 11° 31.324' E. 1 is the fix quality.
- The fix quality can have a value between 0 and 3, defined as follows:
- 0 = no fix
- 1 = GPS or standard positioning service (SPS) fix
- 2 = DGPS fix
- 3 = Precise positioning service (PPS) fix
- 08 is the number of satellites being tracked.
- 0.9 is the horizontal dilution of position (HDOP).
- 133.4,M is the altitude, in meters, above mean sea level.
- 46.9,M is the height of the geoid (mean sea level) above the WGS84 ellipsoid.
- (empty field) is the time in seconds since the last DGPS update.
- (empty field) is the DGPS station ID number.
- *42 is the checksum field.
ArcPad recognizes the following NMEA 0183 version 2.0 or higher sentences.
Note:The first 8 sentences in this table contain the two-letter talker ID, GP. Other talker ID's can be substituted here to equally describe sentences applicable to different receiver types (eg: $GLGGA represents GLONASS fix data).
Sentence | Description |
|---|---|
$GPGGA |
GPS fix data |
$GPGLL |
Geographic position, latitude and longitude |
$GPGSA |
GPS Dilution of Precision (DOP) and active satellites |
$GPGSV |
GPS satellites in view |
$GPRMC |
Recommend minimum specific GPS/TRANSIT data |
$GPRRE |
Range residual error |
$GPVTG |
Track made good and ground speed |
$GPZDA |
Time and date |
$PGRME |
Estimated error information (Garmin Proprietary) |
$PGRMT |
Sensor Information (Garmin Proprietary) |
$PMGNVER |
GPS hardware and software version numbers (Magellan Proprietary) |
$PASHR,POS |
Position information (Ashtech Proprietary) |
$PASHR,SAT |
GPS satellite tracking status information (Ashtech Proprietary) |
$PRWIRID |
Version Information (Rockwell Proprietary) |
$PRWIZCH |
Channel Status (Rockwell Proprietary) |
$SDDPT |
Depth, in meters |
$SDMTW |
Water Temperature, in degrees Celcius |
The NMEA 0183 version 3.0 standard adds the following additional values for the $GPGGA fix quality, which ArcPad recognizes:
- 4 = Real Time Kinematic (RTK) fixed solution
- 5 = Real Time Kinematic (RTK) float solution
- 6 = Estimated dead reckoning
- 7 = Manual input mode
- 8 = Simulation mode
Most receivers output a limited number of NMEA 0183 sentences. ArcPad uses data from a number of NMEA 0183 sentences to display all of the information in the GPS Position Window as well as to populate the fields associated with the GPS Tracklog. When information is not displayed in the GPS Position Window it is usually the result of ArcPad not receiving the required NMEA 0183 sentence from the receiver.