Page | 7 January 23, 2017
The settings above will work for any NTRIP caster that is providing correction data from just one
reference station or a small number of reference stations, where the rover is selecting the reference
station by selecting a specific NTRIP mount point.
If a connection to an RTK network is made, the network usually either selects the nearest physical base
station or it creates a virtual reference station for the rover’s position. In these cases, the network needs
to know the position of the rover before any RTK corrections can be provided, so the rover needs to
send its own position back to the network periodically, usually as an NMEA GGA message.
A connection to an RTK network can be established by sending the following commands:
NTRIPCONFIG NCOM1 CLIENT V1 192.168.13.113:2101 RTCM_31 flex6 Fl3x6
INTERFACEMODE NCOM1 RTCMV3 NOVATEL OFF
LOG NCOM1 GPGGA ONTIME 5
The first command establishes the connection to the caster and requests data from the mount point
“RTCM_31”. The second command tells the receiver to handle the incoming data as RTCM version 3
correction data and to send any messages back to the NTRIP caster in clear text. The third command
sends the receiver’s position back to the caster once every 5 seconds. This will allow the RTK network to
provide the most suitable correction data to the receiver at all times.
To verify that the receiver is actually using the incoming correction data, send one of the following
commands to the receiver:
LOG GPGGA ONCE
LOG BESTPOSA ONCE
The possible replies will be similar to:
$GPGGA,170244.00,5201.7048514,N,00441.4288544,E,4,16,0.7,6.634,M,43.40,M,01,00
13*55
#BESTPOSA,USB1,0,68.5,FINESTEERING,1921,493424.000,00000000,b1f6,14039;SOL_COM
PUTED,NARROW_INT,52.02841415871,4.69048086004,6.6410,43.4000,WGS84,0.0192,0.01
58,0.0403,"13",1.000,0.000,16,16,16,16,00,21,00,33*1987b852
In the $GPGGA message, the (highlighted above) GPS status type “4” indicates the receiver is currently
in RTK FIX mode (the most accurate mode available). The “NARROW_INT” indication in the #BESTPOSA
message also indicates the most accurate operation mode.