Campbell Scientific CR10X Measurement and Control System - Manual (Page 239)

APPENDIX B. CONTROL PORT SERIAL I/O INSTRUCTION 15
B-7
typically have a defined serial output protocol
called NMEA 0183. NMEA 0183 is an interface
protocol created by the National Marine
Electronics Association (http://www.nmea.org/).
The NMEA 0183 Standard defines electrical
signal requirements, data transmission protocol,
timing and specific sentence formats for a 4800
baud serial data bus.
The primary advantage of this data string when
used with P15 is that data is separated with
commas. Since P15 only interprets and decodes
numerical values the commas are treated as data
delimiters resulting in each navigation value
residing in a unique input location.
Two common message strings that come out of
GPS receivers are the GGA and VTG
messages. The GGA message includes time,
position and fix related data for the GPS
receiver. The VTG message conveys the
actual track made good and the speed relative
to the ground. Example are listed below.
EXAMPLES:
GGA Position String - 63 characters including CRLF
$GPGGA,174548,4146.008,N,11151.240,W,1,6,001.9,1113,M,-017,M,,*40CRLF
Field Data Description
1. $GPGGA message identification
2. 174548 UTC of position (i.e., Greenwich mean Time)
3. 4146.008 Latitude
4. N N (North) or S (South)
5. 11151.240 Longitude
6. W W (West) or E (East)
7. 1 GPS Quality Indicator: 0=No GPS Available, 1=GPS Available, 2=DGPS
8. 6 Number of Satellites in use
9. 001.9 Horizontal Dilution of Precision (HDOP).
10. 1113 Antenna Altitude
11. M M = Meters
12. -017 Geoidal Separation in Meters.
13. M M = Meters
14. *40 Checksum
15. CRLF Carriage Return Line Feed
VTG Direction and Speed - 37 characters including CRLF
$GPVTG,010,T,356,M,5.39,N,10.0,K*4FCRLF
Field Data Description
1. $GPVTG message identification
2. 010 Track made good in degrees True
3. T True
4. 356 Track made good in degrees Magnetic
5. M Magnetic
6. 5.39 Speed over ground in Knots
7. N Knots
8. 10.0 Speed over ground in Kilometers per Hour
9. K Kilometers per Hour
10. *4F Checksum
11. CRLF Carriage Return Line Feed