January 20, 2019

RTK Modems

The position obtained from the GNSS system is corrected by using the RTK correction signal ( the difference in between the right truth position and the position obtained from the GPS system). Base Station or VRS is to give GPS unit the information about the correct position.  Then to provide ( transmit) this RTK correction through  RTK modems  to the GPS receivers, featured with ability to receive RTK correction signal.


The basic functions :

Using two GSM SIM cards ( two different mobile operators) in the one RTK modem. When one ( which was present at the previous moment), fails ( 2G/3G/4G -LTE), the very second one has to be switched on and start to work properly in 1-2 seconds. This time is short enough that the automatic steering system does not fail to work properly.


  • Data and basic parameters remote access ( playback, record and managing).
  • Diagnostics reports ( GSM/ VRS communication, Head unit messages).
  • Diagnostics reports ( GSM/ VRS communication, Head unit messages).
  • Modem communication protocol TCP, FTP and UDP
  • GSM Quand band 850/900/1800/1900 Mhz
  • Communication via CANBUS

The transmission correction – description ( RTKM D unit - input/output description ):

1. The device is detecting the presence of the GPS signal on the port J7 ( GPS connection). If the sentence GGA is valid, that means GPS is connected. If the sentence GGA ( GGA sequence – GGA data string) is not valid up 10 sec, GPS is disconnected.

2. If GPS connection is detected, there can be done the connection to the NTRIP server ( if defined IP address, port, mounting point, user name and access password).

3. Two separate and independent SIM cards to receive 2G/3G/4G – LTE signal. When the connection with the first SIM is not present up to 10 s ( 5 times), it is automatically switched to the other SIM. The detection process starts as mentioned in (1.)

4. Both GPS connections ( SIM cards) are receiving the same correction signal ( GGA sentence) to ensure that connections are getting the very same signal.