ashtech GG Surveyor, Reference Manual

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Command/Response Formats 141
Com
m
and
s
$GPGSA/$GLGSA
The response message is output in two messages with different headers. The first
message contains GPS satellite information in the form:
$GPGSA,c1,d1,d2,d3,d4,d5,d6,d7,d8,d9,d10,d11,d12,d13,f1,f2,f3*cc
The second message contains GLONASS satellite information in the form:
$GLGSA,c1,d1,d2,d3,d4,d5,d6,d7,d8,d9,d10,d11,d12,d13,f1,f2,f3*cc
The satellite PRN displayed in each of the ss fields of the GPGSA message is associated with one of
the 12 GPS channels in the receiver, where the first ss field corresponds to the satellite locked to
channel 1 and the last corresponds to the satellite locked to channel 12. The satellite PRN displayed
in each of the ss fields of the GLGSA message is associated with one of the 12 GLONASS channels in
the receiver, where the first ss field corresponds to the satellite locked to channel 13, and the last
corresponds to the satellite locked to channel 24.
Table 6.52 outlines the GSA response message structure.
Examples:
$GPGSA,M,3,15,,20,01,22,14,21,25,,,,29,01.8,01.0,01.5*O F
Table 6.53 outlines the GPGSA response message.
Table 6.52: GSA Structure
Field Significance
c1 Mode
M: manual
A: Automatic
d1 Mode
2: 2D 3:3D
d2-d13 Satellites used in position computation (range 1 to 32 for $GPGSA message,
and 33 to 56 for $GLGSA message)
f1 PDOP (range 0 - 99.9 for mixed constellation)
f2 HDOP (range 0 - 99.9 for mixed constellation)
f3 VDOP (range 0 - 99.9 for mixed constellation)
Table 6.53: Typical GPGSA Response Message
Item Significance
$GPGSA Header
M Manual mode