P4P behavior during Litchi WP mission has me stumped

[TylerB23]

Hey everyone

I've looked everywhere for an answer to this and have tried multiple suggestions I found, but nothing was exactly like the problem I'm having. So let me set it up the best I can.

I used to work for a college doing video production and one of the projects there was to do a repeatable aerial time lapse (since I'm part 107) and orbit a construction site. We purchased a P4P+ months before this project came about and liking it so much, I got a regular P4P because I found out that the + doesn't integrate with 3rd party apps.. so when we started flying around the site, we used the college AC and my RC. Litchi was used on an (college owned) iPhone8+ with the middle of the site as the POI and 5 WP with curved lines. The results were fantastic and flawless! Fast forward 9 months and I've left the college, but they have hired me out to continue the project. I go to fly the same automated route for the first time with my P4P drone and RC now on a new iPad 9.7" (wi-Fi only bc I just do a hotspot if I need to) and it is an absolute mess. It's the first time I ever used Litchi on my own equipment too, so I had no idea this would happen. The drone drifts off center of the POI and sometimes doesnt even have the correct heading and flys the route without turning to face the POI and then seems to try and "catch up" to itself and get back on center. It seems to be a compass issue in my opinion, but I'm all out of ideas or fixes.

I've created two similar test routes shown below of various size/speed at my house and have gotten the same results. In the video HERE, my house (POI) is the one with the big red deck. Can anyone give any insight at all as to what may be the problem? I've tried calibrating everything every way I could find mentioned, upgrade/downgrade firmware, factory resets, you name it... but open to any and all suggestions. Can't send away to DJI until winter as I use it regularly for business and flies fine under my control.






Thanks!

 

[WV. Rootman]

Is your compass fine at the startup?
I can be way off, but it sounds like your mobile is having a processing problem. Make sure everything else is turned off.
Try rebooting the app.

 

[TylerB23]

Is your compass fine at the startup?
I can be way off, but it sounds like your mobile is having a processing problem. Make sure everything else is turned off.
Try rebooting the app.

Rootman, by mobile are you talking about the iPad or controller? I used to fly with an iPhone but that belonged to the college. My ipad has wifi off and all other apps closed. It doesn't have LTE, but I've experienced the same issues when tethered to my phones hotspot just as experiment. I even restarted the ipad today which I usually always leave on.

Everything reads normal with little green bars (IMU/Compass) in DJI GO 4. When I hold it facing west, the compass faces west. Same with N, S, E. Two things I did notice that i forgot to mention... 1. when hovering there is a slight spin to the right even after recalibrating sticks. and 2. in the second half of the video where the drone is infront of my house, the heading shown in Litchi points directly to, maybe even a little to the right, of the POI.. but all in all LOOKS correct in the app, but when I look at it in FPV window during the WP mission, it's clearly pointing to the left of the POI and is instead looking at my neighbors house. I do experience occasional drifting when flying it myself but it's random and not hard to correct.

 

[TylerB23]

Just as a comparison, here is a take from the route at the college that is correct, flown with the P4P+ and my controller. While the three routes aren't the same and the timelapse settings are different as well, especially for the test, you can still see how the route is pretty good and the POI is centered throughout vs my tests with my P4P. The difference is night/day.
VIEW VIDEO

 

[WV. Rootman]

Sorry about your problem. That one has me stumped.

 

[David_Cambridge]

When you set up a route with your equipment using DJI Go, does the route get followed properly?

There are so many things that have changed, that you will need to break the problem down to figure out where the problem system is.

If the system works with the DJI waypoint mission but not the Litchi, it is someplace in the Litchi-drone subsystem. If the DJI waypoints don’t work properly, it is in the drone system itself, and Litchi is probably not involved. Also try the other DJI controlled flight settings like Tap and Fly to see if they all work properly.

Hover with Go, and make sure the camera is steady, and pointed in the right direction. Rotate slowly and watch the camera carefully for and odd movements. If the gimbal doesn’t move smoothly, it could be a problem with it. There are cable connections between the camera and the aircraft. Normally the are routed to insure that they allow the camera to move independently from the drone, but at least on the P3’s it was possible to dislocate the cable enough to restrict the camera movement.

Is the drone itself failing to follow the route, or is it the camera not looking at the correct point?

 

[tribar]

Could you provide links of the 2 missions in the Litchi HUb?
I can't detect waypoints 1 and 2 in the smaller one, which seems strange to me.
Also have you tried an orbit with litchi, if so what was the result?

 

[Harleydude]

Hey everyone

I've looked everywhere for an answer to this and have tried multiple suggestions I found, but nothing was exactly like the problem I'm having. So let me set it up the best I can.

I used to work for a college doing video production and one of the projects there was to do a repeatable aerial time lapse (since I'm part 107) and orbit a construction site. We purchased a P4P+ months before this project came about and liking it so much, I got a regular P4P because I found out that the + doesn't integrate with 3rd party apps.. so when we started flying around the site, we used the college AC and my RC. Litchi was used on an (college owned) iPhone8+ with the middle of the site as the POI and 5 WP with curved lines. The results were fantastic and flawless! Fast forward 9 months and I've left the college, but they have hired me out to continue the project. I go to fly the same automated route for the first time with my P4P drone and RC now on a new iPad 9.7" (wi-Fi only bc I just do a hotspot if I need to) and it is an absolute mess. It's the first time I ever used Litchi on my own equipment too, so I had no idea this would happen. The drone drifts off center of the POI and sometimes doesnt even have the correct heading and flys the route without turning to face the POI and then seems to try and "catch up" to itself and get back on center. It seems to be a compass issue in my opinion, but I'm all out of ideas or fixes.

I've created two similar test routes shown below of various size/speed at my house and have gotten the same results. In the video HERE, my house (POI) is the one with the big red deck. Can anyone give any insight at all as to what may be the problem? I've tried calibrating everything every way I could find mentioned, upgrade/downgrade firmware, factory resets, you name it... but open to any and all suggestions. Can't send away to DJI until winter as I use it regularly for business and flies fine under my control.


View attachment 111727View attachment 111728



Thanks!

I would compare the iOS versions of the college iPad to your iPad. A lot of these third-party apps are in a constant arms race with Apple. If you have a new iOS on your iPad (and I'm going to guess you do), it may no longer be compatible with whichever version of Litchi you are using.

All this assumes that you are using the same versions of Litchi on both devices. If not, this adds another layer of complexity to the trouble-shooting regimen.

Dollars to doughnuts, you'll find inconsistencies between your iPads that will explain the anomaly.

D

 

[TylerB23]

Thanks for all the suggestions. Just to catch up, I haven't tried orbit. The drone followed the waypoints, it just never had the correct heading most of the time. I just did the same flight for the college last week using my ipad and controller, but their drone, and it was perfect... so it's definitely my drone and not a app/iOS issue... unfortunately. BUT, I think we can call it a compass issue prior to being able to try David's (which I planned on doing this week), due to the flight I had this weekend in the mountains which resulted in recovering a waterlogged and tree top attracted drone.The amount of wrong heading it had was UNREAL and took off into trees seemingly on it's own. SO now I'm debating on Mavic 2 Pro or another phantom 4 pro. I already have an extra battery for it, and if I go with another, I'll have a remote for sale... but I've heard some bad things about the P4P v2 ... any thoughts?

 

[David_Cambridge]

Another thing to consider, now that you have fairly quickly determined that it is your drone, is whether or not your compass itself is magnetized, or something inside the drone is. There have been a number of posts about flyers fixing compass problems by degaussing the drone, and recalibrating the compass. Is the waypoint error just cardinal direction, or is it tilt as well? Is the direction error always off the same way? Do you have any accessories on your drone that could be influencing the compass. Calibrating the compass is supposed to 0 out any fixed magnetic influence that is hard fixed to the drone, but maybe not successfully in this case.

Is it possible that your launch point has some magnetic material near it, such as concrete with rebar inside, or shallowly buried pipe or other magnetic metals close to the surface?

Put your drone on the ground, and compare the compass heading with another hand held compass several feet above it, and make sure that both headings agree. If they don’t, you know what the problem is. Severe cases of magnetic anomalies at the takeoff site that are not present when airborne can result in serious crashes resulting from conflicting information between the actual direction of the aircraft and the direction the imu thinks it is pointed in. If you had a more minor version of this, you wouldn’t necessarily crash, but your gps path would be ok, but the direction the drone is pointing would be wrong. This would be equally true with a Litchi route or a DJI route.

 

[TylerB23]

Another thing to consider, now that you have fairly quickly determined that it is your drone, is whether or not your compass itself is magnetized, or something inside the drone is. There have been a number of posts about flyers fixing compass problems by degaussing the drone, and recalibrating the compass. Is the waypoint error just cardinal direction, or is it tilt as well? Is the direction error always off the same way? Do you have any accessories on your drone that could be influencing the compass. Calibrating the compass is supposed to 0 out any fixed magnetic influence that is hard fixed to the drone, but maybe not successfully in this case.

Is it possible that your launch point has some magnetic material near it, such as concrete with rebar inside, or shallowly buried pipe or other magnetic metals close to the surface?

Put your drone on the ground, and compare the compass heading with another hand held compass several feet above it, and make sure that both headings agree. If they don’t, you know what the problem is. Severe cases of magnetic anomalies at the takeoff site that are not present when airborne can result in serious crashes resulting from conflicting information between the actual direction of the aircraft and the direction the imu thinks it is pointed in. If you had a more minor version of this, you wouldn’t necessarily crash, but your gps path would be ok, but the direction the drone is pointing would be wrong. This would be equally true with a Litchi route or a DJI route.

I'd try these things, but it's now in pieces from the crash this weekend. As soon as I am here for 30 days as per the rules, I'll be posting an ad of things for sale. (LIKE NEW: Remote, 2 chargers, extra props, extra battery and FOR PARTS: Camera) The rest is a complete loss. If anyone is interested in these things before I'm able to post officially in the classifieds or another forum, just PM me.

Thanks for all the insight everyone!