RTK

The Certus internal GNSS receiver(s) supports RTK GNSS which uses correction data (RTCM messages) from a nearby base station to provide accuracy of up to 0.01 m in real time. An RTK system requires additional infrastructure equipment to generate and receive corrections data, and is not practical for all applications. Customers who require this level of accuracy but do not need it in real time should consider using Kinematica.

There are two different methods for receiving RTK corrections:

• Network
• Radio modem

For applications where Certus can achieve internet access, network RTK corrections (NTRIP) are recommended.

For applications that are unable to access the internet, radio modems can be used to communicate between Certus and the base station, see .

Note: If you do not need high accuracy positioning in real time, for example if you are planning to use Kinematica to post-process log files, an RTK system may not be necessary at all.

Network RTK Corrections (NTRIP)

NTRIP can be configured as follows:

1. Using the Certus web UI NTRIP Client in the Configuration Menu.

2. Using the Certus Manager application, select NTRIP Client under the Tools menu.

Any of these NTRIP clients can connect to a network RTK service to stream RTK corrections to Certus. This requires that the client is connected to the internet, and a valid subscription with a local network RTK service. Contact Support if you need assistance in setting up for network RTK corrections.

Radio Modem RTK Corrections

Trimble R4 Base Station

Trimble TDL 450L Radio Modem

Base station radio modem RTK corrections require both a base station and a radio modem receiver. The base station is set up at a fixed location and transmits corrections to the radio modem receiver that is connected to the mobile Certus unit (the “rover”). The radio modem receiver and Certus unit must remain within radio range of the base station to receive these corrections. The base station should be located no more than 50 km from the Certus, and ideally closer. Advanced Navigation recommends contacting a local surveying company for assistance setting up a base station.

RTCM Messages

The following RTCM v3.3 messages are recommended for the internal GNSS receiver in Certus.

Message Number	Description
1005	Stationary RTK reference station ARP
1006	Stationary RTK reference station ARP with antenna height
1007	Antenna descriptor
1033	Receiver and antenna description
1074	GPS MSM4
1075	GPS MSM5
1077	GPS MSM7
1084	GLONASS MSM4
1085	GLONASS MSM5
1087	GLONASS MSM7
1094	Galileo MSM4
1095	Galileo MSM5
1097	Galileo MSM7
1124	BeiDou MSM4
1125	BeiDou MSM5
1127	BeiDou MSM7
1230	GLONASS code-phase biases
4072.0	Reference station PVT
1002	Deprecated (supported but not recommended)
1004	Deprecated (supported but not recommended)
1008	Deprecated (supported but not recommended)
1010	Deprecated (supported but not recommended)
1012	Deprecated (supported but not recommended)
1019	Deprecated (supported but not recommended)
1020	Deprecated (supported but not recommended)
1044	Deprecated (supported but not recommended)
1045	Deprecated (supported but not recommended)

Recommended RTCM v3.3 messages