How to fly under bridge or thru tunnel with no GPS?

[Tgoke]

With Phantom 4, I tried to fly under a bridge but of course you lose GPS and it decided to hover and land, in this case WATER! is there a setting I have missed to allow continued flight even without GPS?

 

[Meta4]

With Phantom 4, I tried to fly under a bridge but of course you lose GPS and it decided to hover and land, in this case WATER! is there a setting I have missed to allow continued flight even without GPS?

If you lose GPS, the drone doesn't hover or land ... it keeps flying.
Take your Phantom to a large, open area, well away from trees or other obstacles and switch the flight mode switch to Atti and you will see what actually happens when your drone doesn't have GPS.

 

[Pygar70]

Were you still connected to the drone when it hit the water? Was it responding to controls? I would think that you'd have to lose both your control signal and GPS for the drone to hover and then, once the battery level dropped, land itself without initiating RTH. However, without GPS it would likely drift and hit something first - especially in a confined space.

 

[Andy9]

Yes, if this happened you must have lost both GPS and the RC signal.
If you still had a signal then it should by itself just switch to ATTI as Meta4 said. But you should have the visual if you want to fly it back or to continue the flight.
More problems you'll have with flying in a tunnel. It is better to switch to ATTI before you enter the tunnel.
As tunnels are usually dark you will lose the VLOS and this is a perfect situation for a crash.

 

[jephoto]

Another suggestion for setup before you enter a tunnel or bridge is to set the Loss of signal setting to Hover, rather than RTH and - depending on how tight the space is- use Tripod mode so your side Obsticle Avoidance sensors are activated. You won’t go very fast but it Should prevent you from drifting into the walls.

 

[Meta4]

use Tripod mode so your side Obsticle Avoidance sensors are activated. You won’t go very fast but it Should prevent you from drifting into the walls.

Obstacle avoidance won't work without GPS.
The drone needs GPS to be able to brake.

 

[jephoto]

Ah. Didn’t realize that. Good thing I didn’t test it…

 

[Andy9]

The only safe way to fly through the tunnel is walking behind it so you can see it all the time, LOL!
Everything else is searching for troubles.