Kongsberg Seatex AIS 100, Instruction Manual

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Seatex AIS 100 Instruction Manual, rev. 5 External interfaces
74
GNS – GNSS fix data
Fix data for single or combined satellite navigation systems (GNSS).
This sentence provides fix data for GPS, GLONASS, possible future
satellite systems and systems combining these. This sentence could be
used with the talker identification of GP for GPS, GL for GLONASS,
GN for GNSS combined systems, as well as future identifiers. Some
fields may be null fields for certain applications, as described below.
If a GNSS receiver is capable simultaneously of producing a position
using combined satellite systems, as well as a position using only one
of the satellite systems, then separate $GPGNS, $GLGNS, etc.
messages may be used to report the data calculated from the
individual systems.
If a GNSS receiver is set up to use more than one satellite system, but
for some reason one or more of the systems are not available, then it
may continue to report the positions using $GNGNS, and use the
mode indicator to show which satellite systems are being used.
NOTE 1 Mode Indicator. A variable length valid character field type with the
first two characters currently defined. The first character indicates the
use of GPS satellites, the second character indicates the use of
GLONASS satellites. If another satellite system is added to the
standard, the mode indicator will be extended to three characters; new
satellite systems shall always be added to the right, so the order of
characters in the Mode Indicator is: GPS, GLONASS, other satellite
systems.
The characters shall take one of the following values:
N = No fix. Satellite system not used in position fix, or fix not valid.
A = Autonomous.Satellite system used in non-differential mode in
position fix.
D = Differential. Satellite system used in differential mode in position
fix.