The Gimbal Mode button allows the user to activate two recently added features of the HoverflyGIMBAL, magnetic heading lock and support for full continuous rotation servos.
You can enable the magnetic heading lock feature by choosing "Use magnetometer assisted heading" under the General Settings tab. Magnetic heading lock is used to force the camera to point in a particular direction regardless of the direction of flight. The HoverflyGIMBAL achieves this by taking a compass reading and maintaining the camera in the chosen compass direction until this feature is disabled.
Support for full continuous rotation servos can be enabled by choosing "Continuous rotation servos" from the drop-down menu on the Servo Settings tab. This support is required for camera mounts which use continuous rotation servos on the tilt and roll axis, including those offered by PhotoShipOne. You must mount the HoverflyGIMBAL on the camera tray and enable this feature in order to use it with these types of camera mount.