iSXblue/SXBlue II GNSS Series Technical Reference Manual
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If the antenna is at a constant height, then altitude aiding should help with accuracy. When using a DGPS
position, average the height over a period of time. The longer the time period, the more accurate this
height value will be. Then take the average height and issue the following command:
$JALT,ALWAYS,h
Where “h” is the ellipsoid height. If you are using the height reported from the GGA message this is
actually geoidal and not ellipsoidal height. In this case, you will need to issue the following command:
$JALT,ALWAYS,h,GEOID
5.2.5
$JLIMIT
This command is used to change the threshold of estimated horizontal performance for which the DGPS
position LED is illuminated. The default value for this parameter is a conservative 10.0 meters. This
command has the following format:
$JLIMIT,limit<CR><LF>
Where ‘Limit‘ is the new limit in meters. The receiver will respond with the following message:
$>
If you wish to verify the current $JLIMIT threshold, the response to the $JSHOW command provides this
information.
5.2.6
$JAPP
This command allows you to request the iSXBlue/SXBlue II GNSS for the currently installed
applications and to choose which application to use. The iSXBlue/SXBlue II GNSS by default comes
pre-installed with WAAS (SBAS) in Application Slot 1 and Auto-Dif in Application Slot 2, but Auto-Dif
requires a subscription that must be purchased from Geneq or an authorized reseller.
To poll the receiver for the current applications, send the following message:
$JAPP<CR><LF>
There are no data fields to specify in this message. The receiver will respond with the following message:
$>JAPP,current,other,[1 or 2],[2 or1]
Where ‘current’ indicates the current application in use and ‘other’ indicates the secondary application
that is not in use currently. 1 and 2 indicate which application slot is used by the applications (see the list
of applications in the table below).
For the sake of the application names, the SBAS application is referred to as WAAS by the
iSXBlue/SXBlue II GNSS internal software.
For example, if the response to $JAPP<CR><LF> is
$>JAPP,WAAS,AUTODIFF,1,2