11 (13)
Copyright. 1999. Nokia Mobile Phones. All right reserved
3. GPS FRAME STRUCTURE
The "GPS information" is needed to check whether the frames from the GPS device are received by
the communicator. From your GPS device manual you can see how the receiver indicates if there
are connections to satellites. The two GPS frames have a different amount of characters depending
on the GPS quality (see Section 3.1) and both are sent automatically from the GPS device once a
second.
Please note that the application needs both NMEA 0183 protocol frames (GGA and VTG) to
function. These frames are described in the next two sections.
3.1 GGA frame
The GGA message includes time, position and fix related data for the GPS receiver. The GGA
message provides 3 decimal points of precision in non-differential (GPS) mode and 4 decimal points
of accuracy differential (DGPS) mode.
The $GPGGA frame:
$GPGGA,085042.0,6126.7939,N,02351.7650,E,2,7,1.02,00174,M,020,M,01,0000*67
Description The example frame
Time (hhmmss.0), UTC of Position 085042.0
Latitude (abcd.efgh), N (North) or S (South) 6126.7939,N
Longitude (abcde.fghi), E (East) or W (West) 02351.7650,E
GPS Quality: 0 = no GPS, 1 = GPS, 2 = DGPS 2
Number of satellites in use 7
Horizontal Dilution of Precision (HDOP) (a.bc) 1.02
Antenna altitude in meters, M = meters 00174,M
Geoidal separation in Meters, M=Meters 020,M
Age of Differential GPS Data. Time in seconds
since the last Type 1 or 9 Update
01
Differential Reference Station ID (0000 to 1023) 0000
Checksum delimiter (asterisk) *
The checksum field, two ASCII characters 67
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