The 3DR UBlox GPS + Compass module is the recommended GPS for Pixhawk, PX4 and APM2.6 (and above) flight controllers using ArduPlane,

Rover and Copter.  These come set-up with the best known GPS configuration and have been thoroughly tested by thousands of users.

This page covers the installation of the GPS+Compass module.  If you are installing a GPS without on-board compass follow the instructions found here. 

For instructions on installing a stand-alone compass follow the instructions here.

Connect the GPS’s 6-pin DF13 connector to the Pixhawk’s “GPS” port and the compass’s 4-pin connector to the I2C port. 

Alternatively the compass can be first connected through

As of ArduCopter 3.2 and recent versions of ArduPlane and ArduRover,

a secondary GPS can be connected to the Pixhawk’s Serial 4/5 port. 

Limited testing suggests that a secondary GPS can reduce the likelihood that GPS glitches will affect the vehicle.

  If the parameters are set-up as shown below, the flight controller will use the GPS with the higher number of satellites

(Note: it will switch when one GPS has at least 2 more satellites than the other).

3DR uBlox GPS with Onboard Compass is compatible with APM 2.6 and includes two cables:

one 4-position cable and one 5-position-to-6-position cable. To connect the GPS module to APM 2.6, connect the GPS port to the APM GPS 

port using the 5-position-to-6-position cable (use the top-entry port, not the side-entry port),

and connect the GPS MAG port to the APM I2C port using the 4-position cable.

This module permits the GPS to be mounted separately from the flight control module so that it can have the best clear (view)

of the sky and allows the compass to be distanced from interfering magnetic fields. When mounting the GPS+Compass module:

Place the module on the outside of your vehicle (in an elevated position if appropriate) with a clear view of the sky, as far as

possible from the motors and ESCs, with the arrow facing forward.

Place the module clear of nearby iron containing metallic objects. (Use nylon or non magnetic stainless steel hardware

and nylon or aluminum standoffs to mount the module).

Start Mission Planner, connect your autopilot, and select the “Connect” tab. Select the “Initial Setup” tab, then select the

left menu “Mandatory Hardware” tab and select the “Compass” tab.

Select the option to Enable the compass and to allow Auto Dec. To manually input the declination, select Declination Website

and enter the magnetic declination minutes and seconds for your location.

Next select your autopilot configuration, for Pixhawk and PX4, select the option Pixhawk/PX4 with the image of the Pixhawk. For

APM 2.6, select APM with External Compass with the image of the GPS with Compass module. These options will automatically

enter the correct orientation for the board. Ensure that you have mounted the GPS with Compass with the arrow facing toward

the front of the vehicle and in the same direction as the arrow on the autopilot.

To input a manual orientation for APM, select the Manual option at the bottom of the screen, and consider the following

factors when selecting an orientation. Note: The information below does not apply to Pixhawk and PX4; for these autopilots,

select the Pixhawk/PX4 option to assign the correct orientation.

§  If the GPS / Magnetometer board is mounted in its correct direction (arrow pointing forward) and the Flight controller board

is also mounted right side up with its arrow pointing forward, the (COMPASS_ORIENT) parameter will need to be set to (Roll 180)

or “8” because the compass is upside down under the GPS modules antenna.

§  If the Flight controller board is put in an alternate orientation, the Orientation (i.e. COMPASS_ORIENT parameter) should be

set according to the gps’s attitude to the flight controller.  So for example if both the Flight controller and the GPS+compass module

were mounted on the bottom of the vehicle (a ridiculous example) then you would leave the Compass orientation as ROTATION_

ROLL_180.  If however you wanted to mount the GPS+Compass right-side-up you would pick Orientation “ROTATION_NONE”

because the original rotation was Roll 180, then you add the compass rotation which is another roll 180 = Roll 360 = no rotation.