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4. Software Interface
4.1 NMEA Transmitted Messages
The GPS-20 supported by SiRF Technology Inc. also outputs data in NMEA-0183 format as defined by
the National Marine Electronics Association (NMEA), Standard.
The default communication parameters for NMEA output are 4800 baud, 8 data bits, stop bit, and no
parity.
Table 4-1 NMEA-0183 Output Messages
NMEA Record
GPGGA
GPGLL
GPGSA
GPGSV
GPRMC
GPVTG
4.1.1 Global Positioning System Fix Data (GGA)
Table 5-2 contains the values for the following example:
$GPGGA,161229.487,3723.2475,N,12158.3416,W,1,07,1.0,9.0,M, , , ,0000*18
Table 4-2 GGA Data Format
Name
Message ID
UTC Time
Latitude
N/S Indicator
Longitude
E/W Indicator
Position Fix Indicator
Satellites Used
HDOP
MSL Altitude
Units
Geoid Separation
Units
Age of Diff. Corr.
Diff. Ref. Station ID
Checksum
<CR> <LF>
Table 4-3 Position Fix Indicator
Value
0
0 Fix not available or invalid
1
GPS SPS Mode, fix valid
2
Differential GPS, SPS Mode, fix valid
3
GPS PPS Mode, fix valid
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GPS-20 Operating Manual
Description
Global positioning system fixed data
Geographic position- latitude/longitude
GNSS DOP and active satellites
GNSS satellites in view
Recommended minimum specific GNSS data
Course over ground and ground speed
Example
$GPGGA
161229.487
3723.2475
N
12158.3416
W
1
07
1.0
9.0
Meters
M
Meters
Meters
M
Meters
second
0000
*18
5F-1, 125, Roosevelt Road, Sec. 5, Taipei, Taiwan 116
Units
GGA protocol header
Hhmmss.sss
ddmm.mmmm
N=north or S=south
dddmm.mmmm
E=east or W=west
See Table 5-3
Range 0 to 12
Horizontal Dilution of Precision
Null fields when DGPS is not used
End of message termination
Description
E-Mail:
info@rikaline.com.tw
Rikaline
Description
web:
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11
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