155
Commands
$GPGSA
The GSA message contains indicators for current position mode (see PMD
command on page 82), a list of the satellites being used to compute position, and
the values for PDOP, HDOP, and VDOP. This message is not output until positions
are being computed. The response is output in the format:
$GPGSA,c1,d2,d3,d4,d5,d6,d7,d8,d9,d10,d11,d12,d13,d14,d15,d16,d17*hh
Table 4.80 defines the message format.
Typical GSA message:
$GPGSA,A,3,31,29,23,26,,21,17,09,08,,03,,01.7,01.0,01.4*0B
Table 4.81 describes the typical GSA response message.
Table 4.80. $GPGSA Message Format
Parameter Significance
c1 Position mode indicator:
• A - Automatic mode
• M - Manual mode
A, M
d1 Position mode indicator:
• 2 - 2D mode
• 3 - 3D mode
2, 3
d3-d14 These twelve fields represent the receiver’s twelve channels
listed in ascending order. The number 17 appearing in field
d5 indicates that G12 channel 3 is locked on satellite 17. If a
given channel is not locked on a satellite, the corresponding
field will be empty.
1 - 32
d15 Current PDOP value 0 - 99.9
d16 Current HDOP value 0 - 99.9
d17 Current VDOP value 0 - 99.9
hh Checksum 2-character hex
Table 4.81. Typical $GPGSA Message
Field Description
$GPGSA Header
A Indicates automatic 2-D/3-D switching mode
3 Indicates 3D position mode
31 G12 channel 1 locked on satellite 15; satellite 15 being used in position computations
29 G12 channel 2 locked on satellite 29; satellite 29 being used in position computations
G12RevD.book Page 155 Tuesday, April 2, 2002 4:33 PM
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