NMEA 0183 sentences recognized by ArcPad

ArcPad supports a number of protocols for communicating with GPS receivers, one 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 receiver.
• 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.

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

ArcPad recognizes the following NMEA 0183 version 2.0 or higher sentences:

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

Most GPS 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 GPS receiver.