Seatex DPS 200 Installation Manual, rev. 4 Installation
32
GSA Message
The GSA message presents DOP values and satellites used in the position solution. If only
GPS or Glonass is used for the reported position solution, the talker ID is GP or GL and the
DOP values pertain to the individual systems. If GPS and Glonass are combined for the
reported solution, multiple GSA messages are produced, one with GPS satellites, another with
Glonass satellites. Each of these GSA messages has talker ID GN, to indicate that the
satellites are used in a combined solution. The message is as specified in NMEA 0183
versions 2.2, 2.3 and 3.0. The message structure is as follows:
$--GSA,m,s,ss,ss,ss,ss,ss,ss,ss,ss,ss,ss,ss,ss,pp.p,hh.h,vv.v*cc
Table 17 describes the GSA message fields.
Field Description
m Mode: M = manual, A = automatic.
s Mode: 1 = fix not available, 2 = 2D, 3 = 3D.
ss Satellites used in position computation: 1-32 for GPS satellites (satellite number), 65-96
for Glonass satellites (64 + satellite number), 0 for unused fields.
pp.p PDOP (range 0 - 99.9).
hh.h HDOP (range 0 - 99.9).
vv.v VDOP (range 0 - 99.9).
*cc Checksum.
Table 17 GSA message fields
GST Message
The GST message presents pseudo-range error statistics. If only GPS or Glonass is used for
the reported solution the talker ID is GP or GL and the error data pertain to the individual
system. If satellites from both the systems are used the talker ID is GN. The message is as
specified in NMEA 0183 versions 2.2, 2.3 and 3.0. The message structure is as follows:
$--GST,hhmmss.ss,r.rrr,a.aaa,b.bbb,e.eee,l.lll,y.yyy,h.hhh*cc
Table 18 describes the GST message fields.
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