iSXblue/SXBlue II GNSS Series Technical Reference Manual
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This section provides information related to the NMEA messages accepted by the iSXBlue/SXBlue II
GNSS optional Local Differential applications. The following table provides a brief description of these
commands.
Table 5-10 Local Differential Commands
Message
Modes used
Description
$JRTK,1
Base
This command is used to display the stored Manual-reference
position
$JRTK,1,Other
Base
This command is used to display the stored Auto-reference position
$JRTK,1,P
Base
Store present (computed) position as reference
$JRTK,1,R
Base
Force Base Station to re-average its location
$JRTK,1,lat,lon,alt
Base
Store entered position as reference (Manual)
$JRTK,5
Base
Show and set transmission status of RTK corrections
$JRTK,6
Base
Show status/progress of base station
$JRTK,9
Base
Save base station location determined during the averaging process
to the Manual-Reference memory
$JRTK,17
Base
Display coordinates currently being used as reference
$JASC,DFX
Base
Activate RTK output on a communication port
$JRTK,12
Rover
Enable/Disable the receiver to go into fixed integer mode
$JRTK,18
Rover
Display distance to base station
Note – The iSXBlue/SXBlue II GNSS stores two different reference positions in distinct memory
locations. The first is called Manual-Reference and the other is called Auto-Reference (that the
receiver obtains automatically by averaging).
$JRTK,1 returns the manually entered reference position. $JRTK,1,OTHER returns the receiver's
automatic reference position that the receiver obtains by averaging.
At startup, the receiver will determine which of these two locations it is nearest to (within 10 meters), and
use that location. If it is not within 10 meters of either of these two locations, it will compute a new
location by averaging and store that location in the Auto-Reference memory. To store this new location in
the Manual-Reference memory, the $JRTK,9 command should be used.
A user can never change the content of the Auto-Reference memory and the receiver will never
automatically change the Manual-Reference memory without the user's request.
To make the base station automatic, all you need to do is turn on the differential output with the
$JASC,DFX command and do a $JSAVE. Then, wherever you put the base station, it will do a quick
average and begin transmitting RTK corrections. Furthermore, if you power down the Base station and
then power it up without changing its location, it will use the previously averaged (which has been saved
in memory). Of course, you can still enter the position manually.
If you move the base station to a new location, the old average gets overwritten, but not the manually
entered location.
If you move it to the manually entered location, it will not do an average; instead it will just start with the
manually entered location.