Just updated to the latest version.
Did a few test flights and the speed of the drone is sometimes -1 of the targeted flight speed.
Anyone have this problem too?
Hi Mr. Guey,
Just a few things to check:
The targeted speed was 2m/s and it was working at 1. If set 1, it would be 0. If I set 3, it would be 2. Sometimes it will go to 3. But I am worried that the image spacing will not be enough.
Are flights logs cached? If not I will have to go and make some.
Thanks for the clarification. Yes, all flight telemetry is automatically saved: Telemetry player in user manual
Just checked with our DJI developer and there is aspecific property of DJI SDK, which can cause the actual speed to be less that set in mission. We have reported this to DJI and hope to receive a fix with the next SDK version. As a workaround, you could try to set the speed to 2.1 m/s instead of 2 m/s.
It is also possible, that your segment is climbing ( for example 10 to 20 meters ) in this case the vertical speed can affect horizontal speed.
Additionally I recommend you to use the simulator mode to check precise behaviour without flying. You can check out how to use simulator in User manual Section 5: Using simulator
I have reported this sort of behavior 4 times already to the UgCS support team in June, July, October and Novenmber 2017 as well as a few days ago. It is very disturbing. The DJI support got 3 tickets from me in 2017 without ever answering.
I'm glad that this DJI SDK bug is being investigated now!
Especially for photogrammetry missions it is very problematic when the calculated values deviate so heavily from the reality. We often have to fly with very slow flight speeds (2m/s) due to the ridiculously slow RAW image trigger intervals with our DJI Phantom 4 "Pro". It shoots one image very 4 seconds with the latest apps! If the flight speed goes down to 0.9m/s then due to an SDK bug, it is not usable anymore.
I have had another frustrating DJI experience during a documentation job:
Setting: Railway track through dense forest, Flight distance: 2 x 2.3 km
In Germany we have to stay within sight of the vehicle so I had to run alongside the drone.
Set flight speed: 2.0m/s > Resulting flight speed: 0.9m/s > impossible to finish mission with available batteries
Set flight speed: 3.0m/s > Resulting flight speed: 3m/s > impossible to finish mission, too fast to keep up by foot
Set flight speed: 1.6m/s > Resulting flight speed: 0.9m/s > impossible to finish mission with available batteries
Set flight speed: 2.1m/s > Resulting flight speed: 2.1m/s > finally... unfortunately, all the landing and reprogramming on the laptop in the dirty field had drained most of my batteries before I had found a setting that seemed to work.. So I had to walk back, re-charge the batteries in the car and go out again.
So from this experience and all the experiences throughout 2017 I am guessing that any entered flight speed below 2.1m/s will most likely result in a true flight speed of 0.9m/s. It is always this number!
Can anyone confirm this?