RTK GPS Heading with Dual u-blox F9P
Last updated
Last updated
Two u-blox F9P modules mounted on a vehicle can be used to accurately compute a heading angle (i.e. an alternative to compass-based heading estimation). The two GPS devices in this scenario are referred to as the Moving Base and Rover.
This feature works on F9P devices that support CAN or expose the GPS UART2 port.
The following devices are supported:
(arkelectron.com)
(www.sparkfun.com)
(store-drotek.com)
(store.mrobotics.io)
(Holybro Store)
(Holybro Store)
(CUAV Store)
:::note
and cannot be used because they do not expose the CAN or UART2 port.
Supported devices are also listed in . :::
The application note does not state the minimal required separation between modules (50cm has been used in test vehicles running PX4).
The UART2 of the GPS devices need to be connected together (TXD2 of the "Moving Base" to RXD2 of the "Rover")
Connect UART1 on each of the GPS to (separate) unused UART's on the autopilot, and configure both of them as GPS with baudrate set to Auto. The mapping is as follows:
Main GPS = Rover
Secondary GPS = Moving Base
Reboot and wait until both devices have GPS reception. gps status should then show the Main GPS going into RTK mode, which means the heading angle is available.
:::note If using RTK with a fixed base station the secondary GPS will show the RTK state w.r.t. the base station. :::
Ideally the two antennas should be identical, on the same level/horizontal plane and oriented the same way, and on an identical ground plane size and shape (, section System Level Considerations).
The antennas can be positioned as needed, but the must be configured: .
Set to Heading (1)
parameter bit 3 must be set (see ).
may need to be set (see ).
Refer to the CAN RTK GPS documentation for each specific device for the setup instructions (such as )
- General setup/instructions.