Litchi Bug(?): Gimbal Interpolate doesn't work when flying at slow speeds

[willryan042]

Hey guys,

I've been scratching my head about this for a while thinking it was pilot error but I'm starting to think it's either a bug or just a hardware limitation.

I've been using Litchi to film timelapses using the waypoint feature. Typically I'll just have a two point mission with only a couple hundred feet between the points. I'll have my mavic rotate a bit, change altitude, move extremely slowly (0.2mph), and — well, here's the problem — ideally have the gimbal smoothly pitch throughout the mission.

I have BOTH waypoints set to interpolate and, for example, I'll have WP1 at -45 degrees and WP2 at -10. But no matter what I do the gimbal just doesn't move throughout the mission.

If I increase the speed of the mavic to say, 15mph, the gimbal moves exactly how I want.

Can anyone shed any light on this? Is it a bug? Or can the gimbal just not move that slowly over the course of 20ish minutes? I've been trying to contact the folks at Litchi but it seems like that's not doable.

 

[lisadoc]

Have you tried adding numerous waypoints between the start and end waypoint (by hitting "insert" between points a number of times) and running it that way? I suspect that the gimbal doesn't have that fine of control between 2 points over such an extended period of time.

 

[willryan042]

Have you tried adding numerous waypoints between the start and end waypoint (by hitting "insert" between points a number of times) and running it that way? I suspect that the gimbal doesn't have that fine of control between 2 points over such an extended period of time.

I've thought of that but haven't tried it yet. My gut says that while it may work, it wouldn't be a smooth transition.

Most of these missions are only about 300ft between point 1 and 2. Maybe it'd be smoother the more waypoints I added in between?

Thinking out loud: So if I want the gimbal to pitch from -40 to -10 over the course of 300ft, that's 1 degree every 10ft. Maybe it would work if I added a waypoint every 10ft and increased the interpolation by 1 degree between each?

Related question: is there a way to keep all the waypoints in a straight line? I could see myself slowly knocking things slightly off course if I start adding a bunch of waypoints.

 

[lisadoc]

Most of these missions are only about 300ft between point 1 and 2. Maybe it'd be smoother the more waypoints I added in between?

That is precisely what I'm suggesting.

Maybe it would work if I added a waypoint every 10ft and increased the interpolation by 1 degree between each?

I don't think you need that many but whatever works for you. If you take the total distance, split it up into equidistant segments. Then you can take the same for the gimbal change and divide accordingly. (e.g. 30 degree gimbal change with 6 equidistant points means you need to change the gimbal 5 degrees between each point. 3 degrees per waypoint with 10 segments, etc.)

Related question: is there a way to keep all the waypoints in a straight line?

Again, it's what I was suggesting.

To explain: on the Litchi app, open your map in Waypoints mode. Add Point 1 (where you want to start). Add Point 2 (where you want to end). Tap on Point 1 to open the menu. At the top left, you'll see two waypoint icons - one with a minus and one with a plus. Tap the plus icon and it will add a waypoint precisely between Point 1 and Point 2 (and precisely on the straight line!). Tap it again, tap the plus icon, and it'll add another point midway between the first two points. Continue ad nauseam. You'll have to add midway points between the other points as well, since it only inserts a new point between the one point you're at and the next point. Make sure you have equidistant points if you want to change the gimbal proportionately.

This is all much easier on Litchi Hub. On the hub, you do the same but it automatically opens the menu. At the top are buttons for "Delete" and "Insert". "Insert" does the same thing. You must be at the first point (not the last) to see the option, as it adds a waypoint between the currently selected point and the next one.

As another hint, since the speed of "Cruising" is automatically chosen for each point, there's no need to change your travel speed to .2 MPH (or whatever you want) for each point. That's a pain if you have lots of points. Simply open your mission settings and change the cruise speed to .2 MPH. Now it will "cruise" for all points at that speed. Unfortunately, for the gimbal changes and headings, you will have to manually enter them for each waypoint (since it inserts a waypoint with a heading of 0 degrees and a gimbal pitch of "disabled" and with 0 degrees (in the Hub. In the app you can change the option but it still gives you 0 degrees for an inserted point).

 

[willryan042]

That is precisely what I'm suggesting.



I don't think you need that many but whatever works for you. If you take the total distance, split it up into equidistant segments. Then you can take the same for the gimbal change and divide accordingly. (e.g. 30 degree gimbal change with 6 equidistant points means you need to change the gimbal 5 degrees between each point. 3 degrees per waypoint with 10 segments, etc.)



Again, it's what I was suggesting.

To explain: on the Litchi app, open your map in Waypoints mode. Add Point 1 (where you want to start). Add Point 2 (where you want to end). Tap on Point 1 to open the menu. At the top left, you'll see two waypoint icons - one with a minus and one with a plus. Tap the plus icon and it will add a waypoint precisely between Point 1 and Point 2 (and precisely on the straight line!). Tap it again, tap the plus icon, and it'll add another point midway between the first two points. Continue ad nauseam. You'll have to add midway points between the other points as well, since it only inserts a new point between the one point you're at and the next point. Make sure you have equidistant points if you want to change the gimbal proportionately.

This is all much easier on Litchi Hub. On the hub, you do the same but it automatically opens the menu. At the top are buttons for "Delete" and "Insert". "Insert" does the same thing. You must be at the first point (not the last) to see the option, as it adds a waypoint between the currently selected point and the next one.

As another hint, since the speed of "Cruising" is automatically chosen for each point, there's no need to change your travel speed to .2 MPH (or whatever you want) for each point. That's a pain if you have lots of points. Simply open your mission settings and change the cruise speed to .2 MPH. Now it will "cruise" for all points at that speed. Unfortunately, for the gimbal changes and headings, you will have to manually enter them for each waypoint (since it inserts a waypoint with a heading of 0 degrees and a gimbal pitch of "disabled" and with 0 degrees (in the Hub. In the app you can change the option but it still gives you 0 degrees for an inserted point).

Thanks so much! And nice tip with the "clicking insert," I've just been clicking on the map which would definitely introduce some error.

I guess I'll just have to play with it and experiment, but I'm wondering what the "limit" is where the gimbal decides "nope, that's too far of a distance and the drone is moving too slow" and I end up where I started. Like with my initial example, 300ft at 0.2mph for 20 minutes is obviously an issue since the gimbal didn't move. I messaged the Litchi page on Facebook to hopefully get their input on this.

I'll start with 5 or 6 waypoints and cross my fingers that it works.

 

[lisadoc]

Keep us updated, as I run time-lapse missions as well (but without the gimbal changes). Location, height, and heading changes for time-lapse missions have worked for me without issue, no matter how small the increment.

I may just have to try one with gimbal changes as well.

 

[willryan042]

Will do, thanks for the tips. And same here, altitude and heading changes are smooth as butter. Just trying to get the last piece of the puzzle to work.

What's your process for shooting them? I've tried several different methods but the best option so far has been shooting JPEG at 2s intervals. I'd love to shoot RAW but it looks like the shortest interval is only 5s which is pretty short when you're only shooting for 20ish minutes.

Couple recent ones I've done:

Instagram post by will ryan • Oct 13, 2017 at 2:18pm UTC

Instagram post by will ryan • Oct 9, 2017 at 1:42pm UTC

Instagram post by will ryan • Oct 6, 2017 at 12:56pm UTC

 

[lisadoc]

What's your process for shooting them? I've tried several different methods but the best option so far has been shooting JPEG at 2s intervals.

Because of that, I shoot in 4K video instead of stills, then speed up the footage by 3500% or so. I also stabilize the footage in Premiere using "warp stabilizer".

 

[lisadoc]

Couple recent ones I've done:

Very nice shots...

 

[willryan042]

Got a concrete update after messaging them on FB:

"The hardware limitation is that the gimbal cannot move slower than 0.1deg/sec Please be aware there was a bug with one or two versions of Litchi where it would not move slower than 1deg/sec, but this is fixed in our latest versions."

So they absolute slowest (and I wonder if you'd actually want to go a touch faster than this just to ensure it works) is 6deg/min. So depending on the shot, you could probably set up a super slow gimbal tilt for 8-10minutes of a mission flying at slow speeds, then have it stay still. I can work with that!

 

[lisadoc]

Awesome. Thanks for the update!