Vector Sensor Reference Manual
81
6.6.3
GSA Data Message
The GSA message contains GPS DOP and active satellite information. Only satellites used in the
position computation are present in this message. Null fields are present when data is unavailable
due to the number of satellites tracked. Table 6-8, breaks down the GSA message into its
components. This message has the following format.
$GPGSA,a,b,cc,dd,ee,ff,gg,hh,ii,jj,kk,mm,nn,oo,p.p,q.q,r.r *cc<CR><LF>
Table 6-8 GSA Data Message Defined
Field
Description
a
Satellite acquisition mode M = manually forced to 2D or 3D, A = automatic swap
between 2D and 3D
b
Position mode, 1 = fix not available, 2 = 2D fix, 3 = 3D fix
cc to oo
Satellites used in the position solution, a null field occurs if a channel is unused
p.p
Position Dilution of Precision (PDOP) = 1.0 to 9.9
q.q
Horizontal Dilution of Precision (HDOP) = 1.0 to 9.9
r.r
Vertical Dilution of Precision (VDOP) = 1.0 to 9.9
*cc
Checksum
<CR><LF>
Carriage return and line feed
6.6.4
GST Data Message
The GST message contains Global Navigation Satellite System (GNSS) psuedorange error statistics.
Table 6-9, breaks down the GST message into its components. This message has the following
format.
$GPGST,hhmmss.ss,a.a,b.b,c.c,d.d,e.e,f.f,g.g *cc<CR><LF>
Table 6-9 GST Data Message Defined
Field
Description
hhmmss.ss
UTC time in hours, minutes, seconds of the GPS position
a.a
Root mean square (rms) value of the standard deviation of the range inputs to the
navigation process. Range inputs include pseudoranges and differential GNSS
(DGNSS) corrections
b.b
Standard deviation of semi-major axis of error ellipse (meters)
c.c
Standard deviation of semi-minor axis of error ellipse (meters)
d.d
Orientation of semi-major axis of error ellipse (degrees)
e.e
Standard deviation of latitude error (meteers)
f.f
Standard deviation of longitude error (meters)
g.g
Standard deviation of altitude error (meters)
*cc
Checksum
<CR><LF>
Carriage return and line feed