NMEA
$GPGGA,202530.00,5109.0262,N,11401.8407,W,5,40,0.5,1097.36,M,-17.00,M,18,TSTR*61
The NMEA (National Marine Electronics Association) has defined standards that specify how electronic equipment for marine users communicate. GNSS receivers are part of this standard and the NMEA has defined the format for several GNSS data logs otherwise known as 'sentences'.
Each NMEA sentence begins with a '$' followed by a two-letter prefix identifying the type of sending device (for example 'GP', 'GL' or ‘GN’), followed by a sequence of letters that define the type of information contained in the sentence. Data contained within the sentence is separated by commas and the sentence is terminated with a two digit checksum followed by a carriage return/line feed. Here is an example of a NMEA sentence describing time, position and fix related data:
$GPGGA,134658.00,5106.9792,N,11402.3003,W,2,09,1.0,1048.47,M,-16.27,M,08,AAAA*60
The GPGGA sentence shown above and other NMEA logs are output the same no matter what GNSS receiver is used, providing a standard way to communicate and process GNSS information. For more information about NMEA, see the NMEATALKER command.
|
Field |
Structure |
Description |
Symbol |
Example |
1
$GPGGA
Log header
$GPGGA
2
utc
UTC time status of position (hours/minutes/seconds/ decimal seconds)
hhmmss.ss
202134.00
3
lat
Latitude (DDmm.mm)
llll.ll
5106.9847
4
lat dir
Latitude direction (N = North, S = South)
a
N
5
lon
Longitude (DDDmm.mm)
yyyyy.yy
11402.2986
6
lon dir
Longitude direction (E = East, W = West)
a
W
7
quality
refer to Table: GPS quality indicators
x
1
8
# sats
Number of satellites in use. May be different to the number in view
xx
10
9
hdop
Horizontal dilution of precision
x.x
1.0
10
alt
Antenna altitude above/below mean sea level
x.x
1062.22
11
a-units
Units of antenna altitude (M = metres)
M
M
12
undulation
Undulation - the relationship between the geoid and the WGS84 ellipsoid
x.x
-16.271
13
u-units
Units of undulation (M = metres)
M
M
14
age
Age of correction data (in seconds)
The maximum age reported here is limited to 99 seconds.
xx
(empty when no differential data is present)
15
stn ID
Differential base station ID
xxxx
(empty when no differential data is present)
16
*xx
Check sum
*hh
*48
17
[CR][LF]
Sentence terminator
[CR][LF]
GPS quality indicators
Indicator
Description
0
Fix not available or invalid
1
Single point
Converging PPP (TerraStar-L)
2
Pseudorange differential
Converged PPP (TerraStar-L)
Converging PPP (TerraStar-C PRO, TerraStar-X)
4
RTK fixed ambiguity solution
5
RTK floating ambiguity solution
Converged PPP (TerraStar-C PRO, TerraStar-X)
6
Dead reckoning mode
7
Manual input mode (fixed position)
8
Simulator mode
9
WAAS (SBAS)1