The GPS and Compass are both crucial for the navigation capabilities of the drone. They are both sensitive to noise, although they are different to different types of noise:

• The GPS is receiving signals with very low SNR from the GPS satellite constellation. These signals work at 1.2 GHz and 1.5GHz and any significant electrical noise may prevent the GPS from obtaining a good precision. Sources of noise include especially the electronic speed controllers (ESCs) and the electronic components in the mobile node (beagle bone black, autopilot, USB hub, WiFi? card). The GPS should be as far from these as possible.

• The compass is especially sensitive to magnetic fields, like the ones induced by the current consumed by the motors. For this it needs to be as far from the motors and from the cables powering the ESCs as possible.

Assembly

To avoid these types of noises for both the GPS and the Compass, we found that mounting the GPS outside of the box of electronics is a requirement.

Notes

• Compass calibration is required - otherwise the drone can never reach the target (or toilet-bowls, i.e., drives to the target in an ever shrinking spiral)
• The autopilot firmware has a compasmot test that allows measurements of the compass noise when the motors are are full power. Do it and make sure that interference is smaller than 30%.