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134 GG Surveyor GPS+GLONASS Reference Manual
If the value returned is 1, RAIM has detected errors, and has excluded satellites with
large range errors and corrected the position and velocity. If the quantity of channel-
satellite pairs does not exceed 1, the corrected position and velocities are acceptable
for applications with a probability of 0.999. If the quantity of channel - satellite pairs
exceeds 1, then there is no assurance that the positions and velocities have been
properly corrected. However, in many cases, RAIM corrects the results satisfactorily
even under unfavorable conditions.
If the value returned is 2, RAIM has detected a problem but can not eliminate the
questionable satellites because of too few satellites (e.g., 5 satellites in view). In this
case, the computed data (position and velocity) does not meet the probability of
0.999.
If the value returned is 3, the satellite geometry is poor and detection is unavailable.
This value is always returned if the number of satellites is less than 5.
Finally, if the value returned is 4, RAIM indicates that errors exist (the response
contains channel-satellite pairs), but fails to correct positions and velocities. In such
cases, you can exclude questionable satellites by using the $PASHS,USE or
$PASHS,SVS commands.
GGA: GPS Position Message
$PASHS,NME,GGA,x,s
Enable/disable NMEA GPS position response message on port x, where x is the
output port A, B, or C, and s is ON or OFF.
Example: Enable GGA on port A
$PASHS,NME,GGA,A,ON
$PASHQ,GGA,x
The associated query command is $PASHQ,GGA. This command outputs the GGA
response message on port x, where x is the optional output port.
Example: Output GGA message on port B
$PASHQ,GGA,B
$GPGGA
The response message is in the form:
$GPGGA,m1,m2,c1,m3,c2,d1,d2,f1,f2,M,f3,M,f4,d3 *cc