How is the Mavic's airspeed calculated? Initially I was thinking it was GPS based (ground speed), but then when you are in ATTI (no GPS mode), is the airspeed still displayed?

Maybe the primary airspeed is calculated in the IMU and is just an estimation based on IMU angle and throttle input?

I was just trying to think of a way for DJI to show the Mavic having a head/tailwind and being able to display it. I guess angular drift could determine wind direction, but it wouldn't be able to display the actual wind speed.

It can only display ground speed.  Measure wind speed by putting it in ATTI mode, letting it drift with the wind (careful), and watching the ground speed on the display.  That will tell you speed and direction.

That would be a good idea, but as I understand it, you can't just switch to ATTI mode. It's only activated if you lose GPS signal, but if you lose GPS signal, how is it calculating ground speed?

AG0N-Gary Posted at 2016-12-30 20:04
It can only display ground speed.  Measure wind speed by putting it in ATTI mode, letting it drift with the wind (careful), and watching the ground speed on the display.  That will tell you speed and direction.

And be sure to put the threaded ND filter on too?

As far as I know, the Mavic only calculates its speed with the GPS. With the Inspire 1 and P4 Pro, it shows the speed in ATTI mode if I switch to it (meaning it still has a GPS lock but isn't using it for positioning, only for location/speed) but not if it lost the GPS signal (like indoors) and had to use ATTI. In fact, switching to ATTI mode is the best way to get the most speed out of the Inspire 1.

There's nothing to stop them using the VPS to calculate speed and give you a rough idea of how fast it's going, there are other drones that do that when indoors or with no GPS. My Rolling Spider has no GPS but it tells me its speed from the downward camera.