over the past year the RAW image trigger time with our Phantom 4 "PRO" has increased from 1 image every 2.x seconds to 4s. In early 2017 it was still possible to dial in any number for the trigger speed in UgCS and if you went too low/too fast, you would get an error *during flight* about the camera being too busy to process the current command.. those were the still pretty good days with that drone since we could get the most out of it. I think around 2.5s was a safe value.
In theory nowadays the trigger time should be limited to minimum 3s. But in practice, I get showstopper-error-messages about the trigger time being too fast, until I enter 4s in UgCS. One image very 4 seconds! PRO?! Values also seem to get rounded incorrectly. 3.6s becomes 3s and will give an error that the trigger time is below 3s... we have tried so many times with many versions over months without success.
We really hope that this can be fixed so that we can use UgCS reliably again with that drone.
And regarding rounding. You are right, calculated value round to near lower integer value, and this is right from photogrammetry point of view.
Please remember that time between shots is calculated based on desired forward overlap of images.
In your case we will get calculated value 3.6s
If UgCS will round this value to 4s, you will get lower overlap potentially lead to problem with data processing.
So we decided that UgCS should round to lower value because UgCS should assure specified or better overlapping.
thank you for the clarification. Unfortunately, this rounding "feature" has a massive impact on the gathered data quantity and quality. There are huge differences between 3 and 4s trigger times. Whereas 3s is not working anymore at all for me.
I honestly don't know how to plan a fotogrammetry session properly, if the values I enter become somehow rounded and the resulting overlap factors are a miracle to me by now. It is also very exhausting to do experiments with the software again and again in order to find out, what is going on... which values are delivering what? Flight speed is behaving super weird below 2.1m/s, trigger times become rounded somehow. This renders planning nearly obsolete. Doing proper photogrammetry and documentation work with DJI P4P and UgCS is pure guesswork / trial and error for us at the moment.
Is there anything we can do to make our workflow more robust and predictable, so that we definitely get -at least close to- what we plan for? That would be such a relieve!
DJI accepts only integer values for interval between shots. You can check DJI SDK documenation if you don't want to trust me and to our team. So we have to round calculated interval to some integer value. We prefer to round to lower value because we want to guarantee specifeed overlap.
If you want to make shots in exact places you can use "Additional waypoints" flag in Photogrammetry tool. But here is again hard limit from DJI - new DJI drones can handle only 99 waypoints in single mission.
It's impossible to find ideal solution for non-ideal world and we can't overcome limitations of DJI drones...
Weird speed. Phantom 4 requires around 40 meters to accelerate to the speed ~10m/s in automatic mode.
Why 3s interval will not work in some situations. Ask DJI please... Most probably because not suffecient transfer speed of data to flash card.
Also please read this article - https://www.ugcs.com/en/page/photogrammetry-tool-for-land-surveying, it explains in details how to plan photogrammetry missions.
I think you got me wrong there. I did not want to state in any way a lack of trust in you or offend you or even your whole team. Please do not take my criticism so personally!
I am sure that the underlying problems are caused by constantly changing limitations/rules within the DJI SDK and you are doing your best to adapt your software. UgCS is still my favorite tool for mission planning because of the high level of configurability. Big thumbs up!
During the next flight I will try to achieve a 3s trigger time by manually overwriting the minimal p4p payload/camera trigger time down to lets say 2s and report here, if it worked. Also now I know that I can not fly speeds between 0.9 and 2.0 m/s with that drone (for an unknown reason) and can do my planning accordingly.
I'm very sorry for my inappropriate reaction...
Our 3s in camera profile is a conservative value based on our experience. We get such results too often with shorter time (it's Phantom 3 and 2s between shots):