GPS/Compass

PX4 supports global navigation satellite systems (GNSS) (including GPS, GLONASS, Galileo, BeiDou, QZSS and SBAS) using receivers that communicate via the u-blox, MTK Ashtech or Emlid protocols, or via UAVCAN. It also supports Real Time Kinematic (RTK) and Post-Processing Kinematic (PPK) GPS Receivers, which extend GPS systems to centimetre-level precision.

PX4 can be used with the following compass parts (magnetometers): Bosch BMM 150 MEMS (via I2C bus), HMC5883 / HMC5983 (I2C or SPI), IST8310 (I2C) and LIS3MDL (I2C or SPI). Up to 4 internal or external magnetometers can be connected, though only one will actually be used as a heading source.

The system automatically chooses the best available compass based on their priority (external magnetometers have a higher priority than internal magnetometers). If the primary compass fails in-flight, it will failover to the next one. If it fails before flight, arming will be denied.

GPS + Compass

:::tip When using Pixhawk-series flight controllers, we recommend using a combined GPS + Compass mounted as far away from the motor/ESC power supply lines as possible - typically on a pedestal or wing (for fixed-wing). The internal compass may be useful on larger vehicles (e.g. VTOL) where it is possible to reduce electromagnetic interference by mounting the Pixhawk a long way from power supply lines. On small vehicles an external compass is almost always required. :::

Supported GNSS and/or Compass

PX4 should work with any unit that communicates via the u-blox, MTK Ashtech or Emlid protocols, or via UAVCAN.

GNSS & Compass

This list contains GNSS units (most of which also have a compass). These have been tested by the PX4 dev team, or which are popular within the PX4 community.

Device	GPS	Compass	RTK	GPS Yaw Output	Dual F9P GPS Heading	PPK
ARK GPS	M9N	ICM42688p
ARK RTK GPS	F9P	ICM42688p	✓		✓
Avionics Anonymous UAVCAN GNSS/Mag	SAM-M8Q	MMC5983MA
CUAV C-RTK GPS	M8P/M8N	✓	✓
CUAV C-RTK 9Ps GPS	F9P	RM3100	✓		✓
CUAV C-RTK2 PPK/RTK GNSS	F9P	RM3100	✓			✓
CubePilot Here2 GNSS GPS (M8N)	M8N	ICM20948
CubePilot Here+ RTK GPS	M8P	HMC5983	✓
CubePilot Here3 CAN GNSS GPS (M8N)	M8P	ICM20948	✓
Drotek DP0804 (and other Drotek u-blox GPS/Compasses)	M9N	LIS3MDL
Drotek SIRIUS RTK GNSS ROVER (F9P)	F9P	RM3100	✓		✓
Emlid Reach M+ - PX4 only supports "ordinary" GPS with this module. RTK support is expected in the near future.	✓	✗
Femtones MINI2 Receiver	FB672, FB6A0	✓	✓
Freefly RTK GPS	F9P	IST8310	✓
Holybro DroneCAN M8N GPS	M8N	BMM150
Holybro Micro M8N GPS	M8N	IST8310
Holybro Nano Ublox M8 5883 GPS	UBX-M8030	QMC5883
Holybro M8N GPS	M8N	IST8310
Holybro M9N GPS	M9N	IST8310
Holybro DroneCAN M9N GPS	M9N	BMM150
Holybro H-RTK F9P Helical or Base	F9P	IST8310	✓		✓
Holybro DroneCAN H-RTK F9P Helical	F9P	BMM150	✓		✓
Holybro H-RTK F9P Rover Lite	F9P	IST8310	✓
Holybro DroneCAN H-RTK F9P Rover	F9P	BMM150	✓		✓
Holybro H-RTK M8P GNSS	M8P	IST8310	✓
Holybro H-RTK Unicore UM982 GPS	UM982	IST8310	✓	✓
Hobbyking u-blox Neo-M8N GPS with Compass	M8N	✓
LOCOSYS Hawk A1 GNSS receiver	MC-1612-V2b	optional	✗
LOCOSYS Hawk R1	MC-1612-V2b		✗
LOCOSYS Hawk R2	MC-1612-V2b	IST8310	✗
mRo GPS u-blox Neo-M8N Dual Compass	M8N	LIS3MDL, IST8308
mRo u-blox ZED-F9 RTK L1/L2 GPS	F9P	✗	✓		✓
Septentrio AsteRx-RIB	AsteRx	✓	✓	✓	Septentrio dual antenna heading	✓
Septentrio mosaic-go	mosaic X5 / mosaic H	✓	✓	✓	Septentrio dual antenna heading	✓
Sky-Drones SmartAP GPS	M8N	HMC5983, IST8310, LIS3MDL
SparkFun GPS-RTK2 Board - ZED-F9P	F9P	✗	✓		✓
Trimble MB-Two	F9P	✗	✓	✓
Zubax GNSS 2	MAX-M8Q	LIS3MDL

Notes:

• ✓ or a specific part number indicate that a features is supported, while ✗ or empty show that the feature is not supported. "?" indicates "unknown".

• Where possible and relevant the part name is used (i.e. ✓ in the GPS column indicates that a GPS module is present but the part is not known).

• Avionics Anonymous UAVCAN Magnetometer and Holybro DroneCAN RM3100 Compass/Magnetometer is a compass (not a GPS).

• Some RTK modules can only be used in a particular role (base or rover), while others can be used interchangeably.

• The list may omit some discontinued hardware that is still supported. For example CubePilot Here+ RTK GPS is discontinued and may be removed from the list in a future release. The original Here has already been removed. Check earlier versions if a discontinued module is not mentioned here.

Compass/Magnetometer (Only)

This list contains compasses (magnetometers) without GNSS.

Device	Compass	DroneCan
Avionics Anonymous UAVCAN Magnetometer	?
Holybro DroneCAN RM3100 Compass/Magnetometer	RM3100	✓

Note:

• ✓ or a specific part number indicate that a features is supported, while ✗ or empty show that the feature is not supported. "?" indicates "unknown".

Hardware Setup

Instructions for connecting the GPS (and compass, if present) are usually provided by the manufacturer (at least for more common Autopilot Hardware).

Pixhawk Series controllers typically have a clearly labeled port for connecting the GPS, and the compass is connected to either the I2C or SPI port/bus (depending on the device).

The ARK GPS, ARK RTK GPS, Zubax GNSS 2, CUAV C-RTK2, CubePilot Here3 CAN GNSS GPS (M8N), and Avionics Anonymous GNSS/Mag can also be connected via DroneCAN.

:::warning Pay attention to pinout when connecting the GPS module. While these are all software-compatible, there are several different pin orderings. :::

GNSS Configuration

The "standard" GPS configuration is provided below. Additional device-specific configuration may be provided in PX4 or manufacturer device documentation (e.g. Trimble MB-Two > Configuration).

:::warning The GPS protocol expected by PX4 defaults to u-blox (by default other GPS types like Trimble, Emlid, MTK, will not be detected) The protocol can be configured with GPS_x_PROTOCOL. :::

Configuring the Primary GPS

GPS configuration on Pixhawk is handled transparently for the user - simply connect the GPS module to the port labeled GPS and everything should work.

:::note The default Serial Port Configuration works for most devices. If you are using the Trimble MB-Two you will need to modify the configuration to explicitly set the rate to 115200 baud. :::

Configuring a Secondary GPS (Dual GPS System)

To use a secondary GPS, attach it to any free port, and then perform a Serial Port Configuration to assign GPS_2_CONFIG to the selected port.

The following steps show how to configure a secondary GPS on the TELEM 2 port in QGroundControl:

1. Find and set the parameter GPS_2_CONFIG to TELEM 2.

   • Open QGroundControl and navigate to the Vehicle Setup > Parameters section.

   • Select the GPS tab (1), then open the GPS_2_CONFIG parameter (2) and select TELEM 2 from the dropdown list (3).
2. Reboot the vehicle in order to make the other parameters visible.

3. Select the Serial tab, and open the SER_TEL2_BAUD parameter (TELEM 2 port baud rate): set it to Auto.

After setting up the second GPS port:

1. Configure the ECL/EKF2 estimator to blend data from both GPS systems. For detailed instructions see: Using the ECL EKF > Dual Receivers.

Configuring GPS as Yaw/Heading Source

GPS can be used as a source for yaw fusion when using modules where yaw output is supported by the device (e.g. Trimble MB-Two) or when using some RTK GPS Setups with Dual u-blox F9P.

When using GPS for yaw fusion you will need to configure the following parameters:

Parameter	Setting
GPS_YAW_OFFSET	The angle made by the baseline (the line between the two GPS antennas) relative to the vehicle x-axis (front/back axis, as shown here).
EKF2_GPS_CTRL	Set bit position 3 "Dual antenna heading" to 1 (i.e. add 8 to the parameter value).

:::tip If using this feature, all other configuration should be setup up as normal (e.g. RTK Positioning). :::

Compass Configuration

Compass calibration is covered in: Compass Configuration. The process is straightforward and will autodetect, set default rotations, calibrate, and prioritise, all connected magnetometers.

Developer Information

• GPS/RTK-GPS

  • RTK-GPS

  • GPS driver

  • DroneCAN Example

• Compass

  • Driver source code (Compasses)