General
RTK GPS uses a stationary base station unit on the ground (Base) to send correction data to a mobile GPS unit on the aircraft (Rover). The RTK corrections allow the rover unit to achieve a higher level of precision and accuracy than would be possible otherwise.
The Base (ground) unit must be positioned in a stable location and not moved. The location can be pre-surveyed or the unit can survey the location itself. This document will cover the self survey procedure, known as a survey-in.
Mission Planner has a built-in utility for acquiring and sending RTK corrections. However, this method does not work reliably with newer GPS units. As a result this manual will cover a method of using QGroundControl to generate corrections and then pass them through Mission Planner.
Connection Diagram
QGroundControl is used to connect to the Base RTK GPS unit and preform a survey-in
Mission Planner is used to establish a telemetry connection with the aircraft
This is over a network radio or RFD depending on the aircraft configuration
A Mavlink mirror is opened from Mission Planner
This will allow QGroundControl and Mission Planner to interact with the Mavlink stream from the vehicle simultaneously
QGroundControl connects to the Mavlink mirror
RTK corrections are sent from QGC through the Mavlink mirror, to Mission Planner, and are then forwarded up the telemetry link to the vehicle.
Survey-In Position of Ground Station Using QGC
Position the ground station GPS antenna where it will not be disturbed and with a clear view of the sky.
Connect the base GPS to a Ground Station Computer that will have a wireless link to the aircraft
Open QGroundControl
The program will automatically detect the GPS unit and start a survey-in
The survey-in status can be viewed by clicking the RTK icon in the top menu bar
Do not move the base station after survey-in has begun or during the use of RTK correction data.
If using a TXMod unit, QGC may automatically detect the connection and block Mission Planner from connecting. In this case click disconnect on QGC then connect with Mission Planner or connect using Mission Planner before opening QGC for the survey.
Change the Survey-In Settings or Input Pre-Surveyed Coordinates
Click the icon in the top left of QGC window
Click Application Settings
Go to the General menu on the left
Scroll down to the RTK GPS settings
Here you can change the accuracy, time, or input a pre-surveyed location
Restart QGC to make the settings take effect
Connect to the Aircraft with Mission Planner
Enable the Mavlink Mirror
Connect QGC to the Mavlink Mirror
QGroundControl will automatically send corrections to any vehicle with an active connection
Click the icon in the top left of QGC window
Click Application Settings
Go to the Comm Link menu on the left
Click “Add” at the bottom of the screen
Enter the connection information
XXXXXX
Click save
Highlight the desired entry in the Comm Link menu
Click “Connect” to open a connection