Why the navdata topic doesnt show Linear z velocity in ardrone_autonomy?

asked 2015-04-03 13:38:37 -0500

erivera1802 gravatar image

updated 2015-04-03 13:41:26 -0500

Hi there, I am working with the ardrone_autonomy package, and all seems right, except for the detail that when I echo the /ardrone/navdata topic, all the values seem ok except the Vz, linear Z velocity value. Here is an example of what im getting:

batteryPercent: 18.0

state: 2

magX: -31

magY: -73

magZ: 51

pressure: 75088

temp: 403

wind_speed: 0.0

wind_angle: 45.0000190735

wind_comp_angle: -0.0

rotX: -4.86100006104

rotY: 0.421000003815

rotZ: 4.75699996948

altd: 0

vx: 56.8887748718

vy: 83.2262802124

vz: -0.0

ax: -0.0310622174293

ay: -0.0128604527563

az: 1.00342142582

As you can see, Vz displays 0, and it is constant all the time. I think i saw a person with the same problem, but i couldnt find the web or question again. I hope someone can help me.


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It shows your altitude as 0. Was the drone flying when you captured this?

Tom Moore gravatar image Tom Moore  ( 2015-04-04 06:54:45 -0500 )edit

No, for the picture it wasnt flying. But i have tried also when the drone is flying, and the altitude shows the correct value, bit the linear z velocity, dont

erivera1802 gravatar image erivera1802  ( 2015-04-04 10:55:48 -0500 )edit

You can try checking out the source code to track down the issue, or you can differentiate the altitude data to get Vz.

Tom Moore gravatar image Tom Moore  ( 2015-04-04 11:13:24 -0500 )edit

From my own experience with the AR.Drone 2.0, it never publishes data about vertical velocity (vz). I'm guessing here, but it may because it estimates its speed using the vertical camera and to estimate it's vz then it would have to the size of the objects on the ground which it can't.

jayess gravatar image jayess  ( 2016-04-04 08:05:34 -0500 )edit