First of all, much credit to the Litchi team for a pair of great products! I’m just now getting back to Litchi after several years hiatus, with my new DJI Mini 3. Using Litchi Pilot build 520.
I was testing some functionality, and ran into a strange one, that the Orbit functionality works perfectly in the 3D simulation (in this case “works perfectly” means that it performs the Orbit with the heading and gimbal locked onto the point of interest).
The point of interest is the gazebo.
However, when I actually fly the mission, the gazebo slides off to the right, getting more and more off-center the later in the orbit you are. See the following two screenshots, one from the sim, one from the actual. These screenshots are with the orbit about 85% done.
When you set a POI based on a satellite image, it can off by several meters. It’s just the nature of satellite imagery and its GPS accuracy.
My work around (if it’s critical) is to fly my drone directly over the POI at a safe altitude, then note the Lat/Lon and enter those coordinates for the POI in the mission.
Sam, thanks! I should have also included screen shots at the beginning of the orbit. They are below, and might help. While it looks like the centerpoint is perhaps 5 meters off of the gazebo, by the end of the orbit, the centerpoint is around 25 meters off of the gazebo (by my estimation). I just found that behavior odd, that even if the location to orbit is off a little, that the orbit still wouldn’t remain focused on that spot ±3 meters (if Google is to be believed on the subject of GPS accuracy on DJI consumer drones).
If you haven’t used AirData to view flight log info, it will be worth checking out to see if the centerpoint is in fact moving or not. You can see the actual path that was flown.
It’s very difficult for me to tell from the video screenshots.
Hello; I did an upload to AirData, which does help somewhat to narrow down the problem (I think). As far as I can tell, the drone is flying a perfect orbit around the intended point (the gazebo), and the heading is correct all of the way around (again, to my eye). Which only leaves the camera/gimbal,
The AirData screenshot is below in the late part of the orbit where the video is the most “off”. The line I drew is my best estimate of the pointing direction from the arrow, but the gimbal appears to be looking not along that line, but well off to the left where I drew the small camera icon.
Don’t get me wrong; I’m not complaining; just trying to help identify and sort a problem if there really is one. Thanks!
Below is the gimbal heading during the orbit (enclosed in red box). I don’t see anything there that is obvious; which leads me to believe that the slope might be off a little bit…meaning that the gimbal heading is not changing at the correct rate to keep the POI centered.
After the above post, it occurred to me to just plot the drone heading and the gimbal heading together. Here’s that…they should match right? There’s a 14 to 15 degree difference in the two during the orbit.
EDIT: to be fair, I just noticed that the offset between gimbal and heading is there the entire flight, not just the orbit. Maybe I just need to recalibrate the gimbal?
I tried recalibrating the gimbal, but the results were the same unfortunately.
In the newest flight, I differenced the gimbal heading and the vehicle heading, and it’s a couple of degrees to the left at the beginning of the orbit, steadily increasing to five degrees at the end. This seems to be the cause, because the drone itself flies a nearly perfect circle and the front of the drone always faces the point of interest, as precisely as I was able to tell.
You can try an IMU calibration. Because the gimbal relies on IMU data to compensate for the drone’s movements, a small drift in the IMU can cause the camera to misalign with the heading.
Calibrate the IMU (and gimbal, just to be sure) in the DJI Fly app and then test again, in many cases this fixes the offset issue.
As Litchi staff recommended I’d calibrate the IMU first. Once done I’d calibrate the Gimbal manually. All three of my DJI drones when I use auto gimbal calibration are off anywhere from about 1° to 2°. It may not sound like much but a 2° or more gimbal misalignment can make a difference. I’ve seen several postings over the years in which the gimbal was off anywhere from about 2° to 5° or more when auto calibration was used.
There are a few ways to get it completely centered but some take a bit more time. The quickest and easiest way I align my gimbal and is accurate enough is by laying a piece of white printer paper underneath the front of aircraft. Then look down over the top of the drone from behind it. You can compare the front of the camera sensor in relation to the front of the drones body. If off by about 2° or more you should be able to see it easily enough. This may not be the entire reason yours is off during the Orbit but better to start with it centered as best it can be and then go from there. I have manually adjust all three of mine. Just some suggestions which may help.
