How long before Atti impacts mode when GPS cut?

[Davros007]

Just a query. Flying under a bridge, barn-storming etc. - if one is at speed, what sort of distance before the effects of GPS loss are felt/noticed? Can one “punch through” without noticeable affects, versus going slow and having drift issues etc? I guess also the visual inputs can be critical too, for example at night or over flat water etc.?
Mine is a MP1. But answers in regards other models interesting too.
Interested in being able to decide from a distance the risks of flying, say, through a natural rock-bridge or a large crack over rough waves etc.

 

[Meta4]

Just a query. Flying under a bridge, barn-storming etc. - if one is at speed, what sort of distance before the effects of GPS loss are felt/noticed? Can one “punch through” without noticeable affects, versus going slow and having drift issues etc?

If you are flying straight, there's no effect to notice.
Losing GPS doesn't slow the drone.

 

[Davros007]

If you are flying straight, there's no effect to notice.
Losing GPS doesn't slow the drone.

Cool. Thanks!

 

[Rich QR]

The GPS doesn't give very fast precise updates, but it does a great job of getting the absolute position and velocity correct. The inertial navigation always works, but it is the opposite -- it very quickly reacts to changes in velocity due to wind gusts, control inputs, or whatever, but it doesn't know anything about absolute position, so with time, its notion of your absolute position and velocity gets less precise, causing you to drift. Finally, if you're flying close to the ground, and if the ground has enough texture to lock onto, and if it's light enough for the ground camera to work, the ground camera can stabilize things so that you don't drift much, even without GPS. The ground camera makes relatively stable indoor flight possible.

If you lose GPS, what matters is the amount of time the GPS signal is gone, more than the distance. Quickly flying under a bridge, you'll never notice a problem. Hover under there for a few minutes, and if the ground camera can't stabilize you, expect to start drifting.

The ground camera won't stabilize you over moving water, so if you're talking about a bridge over a river, expect to start drifting if you hang out under there for long.

Practice when you're close enough to see the drone well enough to fly safely, even without GPS or ground cameras. A fairly dark indoor space may let you experience ATTI mode conveniently in a controlled, wind-free environment. Prop guards can mitigate risks of collisions somewhat.