Using the GPS2 RTK with Internet Corrections over GSM
- Configure the GPS2 RTK to use internet based correction source over GSM
- Sign up to an NTRIP service that can supply RTCM v3.x corrections valid for your location
- Ensure both the GSM and NTRIP settings are configured correctly to match the requirements of your SIM card provider and your NTRIP provider.
- Ensure a GSM antenna is connected to the GPS2 RTK.
- Ensure the GPS2 RTK is using the supplied dual frequency GPS+Glonass antenna.
- Ensure a data-capable SIM card is inserted in the SIM card slot on the rear of the GPS2 RTK.
The GPS2 RTK receiver can be configured to receive internet based corrections via. the GSM data link. To enable this mode, select “Corrections using internet based correction source over GSM data connection” in the configuration software.
NOTE 1: Once the GPS2 RTK is configured in this mode, it is important that a GSM antenna is connected to the GPS2 RTK whenever the unit is powered on. If this is not done, then the GSM module may increase the power draw in an attempt to compensate, resulting in excess current consumption from the power supply, and reduced GNSS performance due to increased interference. Hence whenever a GSM antenna is not available, the GPS2 RTK should always be configured either in standalone or radio-modem mode.
Note 2: When configured to receive internet corrections over GSM, the GPS2 RTK will automatically retransmit them from the rear “Modem” serial port at 38400 baud. This allows them to be forwarded on to one or more additional GPS2 RTK receivers using either serial cable or radio modems, and thus potentially allows multiple units to receive corrections from a single NTRIP source.
It is necessary to insert a data-capable SIM card (standard size) into the labelled SIM slot on the rear of the GPS2 RTK. In most cases, no explicit configuration of the SIM card settings is required; the data SIM will simply connect automatically through it’s built in settings. If it is necessary to configure the GPS2 RTK to match your SIM providers settings then please refer to this link.
It is also necessary to subscribe to a provider of internet based corrections, which are provided through a protocol known as an NTRIP caster. There are free NTRIP casters available, but in our experience satisfactory operation has only been attained through subscribing to a paid professional service. It is necessary to carefully configure the GPS2 RTK to match the NTRIP caster settings supplied by your provider: full details on how to configure this can be found here.
Following these steps, the GPS2 RTK should achieve integer RTK differential lock (full accuracy) as long as adequate GSM reception is available, and the GPS2 RTK has a clear view of the sky and is using the supplied dual frequency GPS+Glonass antenna. To verify correct operation, check that the GPS2 RTK is receiving data from the GSM module (the GSMLink LED should light solidly blue), and check that the GPS2 RTK then attains an integer RTK differential lock (the Diff LED should light solidly orange).
Typically, once differential lock has been attained, the GPS2 RTK will retain differential operation as long as GSM dropouts do not exceed more than approximately 30s in duration. Hence the system is robust to driving under bridges, or though small GSM shadows, etc.