Nmea output messages – Linx Technologies RXM-GPS-FM User Manual
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NMEA Output Messages
The following sections outline the data structures of the various NMEA
messages that are supported by the module. By default, the NMEA
commands are output at 9,600bps, 8 data bits, 1 start bit, stop bit, and no
parity.
Six messages are output at a 1Hz rate by default. These messages are
shown in Figure 8.
Details of each message and examples are given in the following sections.
GGA – Global Positioning System Fix Data
Figure 9 contains the values for the following example:
$GPGGA,053740.000,2503.6319,N,12136.0099,E,1,08,1.1,63.8,M,15.2,M,,0000*64
Global Positioning System Fix Data Example
Name
Example
Units
Description
Message ID
$GPGGA
GGA protocol header
UTC Time
053740.000
hhmmss.sss
Latitude
2503.6319
ddmm.mmmm
N/S Indicator
N
N=north or S=south
Longitude
12136.0099
dddmm.mmmm
E/W Indicator
E
E=east or W=west
Position Fix Indicator
1
Satellites Used
08
Range 0 to 33
HDOP
1.1
Horizontal Dilution of Precision
MSL Altitude
63.8
meters
Units
M
meters
Geoid Separation
15.2
meters
Units
M
meters
Age of Diff. Corr.
second
Null fields when DGPS is not used
Diff. Ref. Station
0000
Checksum
*64
End of message termination
Position Indicator Values
Value
Description
0
Fix not available or invalid
1
GPS SPS Mode, fix valid
2
Differential GPS, SPS Mode, fix valid
3–5
Not supported
6
Dead Reckoning Mode, fix valid (requires external hardware)
Figure 9: Global Positioning System Fix Data Example
Figure 10: Position Indicator Values
NMEA Output Messages
Name
Description
Contains the essential fix data which provide location and accuracy
Contains just position and time
Contains data on the Dilution of Precision (DOP) and which satellites are used
Contains the satellite location relative to the receiver and its signal to noise
ratio. Each message can describe 4 satellites so multiple messages may be
output depending on the number of satellites being tracked.
Contains the minimum data of time, position, speed and course
Contains the course and speed over the ground
Figure 8: NMEA Output Messages