RTH in GPS-denied environment result in instant emergency landing

[digitalentity]

In a GPS-denied environment activating RTH (either manually or by failsafe) result in instant emergency landing.

It would be better to create two scenarios:

1. Manual RTH - disallow pilot to activate RTH
2. Failsafe RTH - allow the UAV to drift with the wind and maintain only altitude for a certain timeout to allow GPS to recover, then switch to emergency landing.

[DzikuVx]

was this not covered some time ago with gps-glitch? Emergency landing was supposed to be triggered only after some time passed. Or this is different case?

[digitalentity]

That's a different case. If GPS is lost when RTH is already in progress it will wait for _nav_positiontimeout seconds. However if GPS is not available when RTH is only being activated - instant emergency landing is triggered.

[digitalentity]

Implementation in #745, closing.