Interpolation on waypoint mode - Litchi

[bsartist]

This is from the Litchi manual. The use of the word "keep" I think is what convinced me that dwallersv is correct about focus poi mode. It also implies that "disable" will cause Litchi not to aim the gimbal at all.

• Gimbal Pitch: Choose between "Disabled" where the gimbal pitch control will be manual, "Focus POI" where Litchi will automatically control the gimbal pitch to keep the selected POI in the center of the frame (blue markers), or "Interpolate" where you can specify the gimbal pitch angle at this waypoint. For "Interpolate" to work, the previous or next waypoint need to be set to "Interpolate" as well. Litchi will then automatically adjust the gimbal pitch angle to start and end at the specified angles, and smoothly transition while travelling between the two waypoints.

 

[BryanBTX]

How can you simulate the gimbal movement during flight on a PC?

Well you can't on that part but I was talking about seeing how the drone still looks at the POI.

 

[BryanBTX]

At waypoint 6 I disable the Gimbel pitch but still keep Changing the PIO's in direction of flight.

 

[BryanBTX]

here is the video of that mission.

 

[bsartist]

View attachment 78915

At waypoint 6 I disable the Gimbel pitch but still keep Changing the PIO's in direction of flight.

Gimbal pitch is the up and down aiming of the camera. You are referring to the yaw angle. On a P3S that is controlled by how the AC points. (Other aircraft may have gimbal yaw. But nonetheless the question here is pitch - which is up and down aiming. Not horizontal directional aim).

 

[bsartist]

here is the video of that mission.

Nice video.

So you are saying that for that mission you had gimbal pitch disabled and the camera was still executing those up and down aiming motions automatically?

 

[BryanBTX]

Nice video.

So you are saying that for that mission you had gimbal pitch disabled and the camera was still executing those up and down aiming motions automatically?

Yes

 

[BryanBTX]

Because I had a poi number in that wp I guess.

 

[bsartist]

Yes

Curious. I've actually flown a mission where I did not want the pitch to change for the last few waypoints so I disabled pitch control. The bird continued to change heading to point at the POI but did not change the pitch of the camera. Which is what I expected but different than what you are saying.

 

[BryanBTX]

Curious. I've actually flown a mission where I did not want the pitch to change for the last few waypoints so I disabled pitch control. The bird continued to change heading to point at the POI but did not change the pitch of the camera. Which is what I expected but different than what you are saying.

I think the key is I put a poi even though I have it disabled. Probably would not change if I put "none" in there. I'm heading home I'll do some testing.

 

[bsartist]

I think the key is I put a poi even though I have it disabled. Probably would not change if I put "none" in there. I'm heading home I'll do some testing.

But I have a POI in my last few waypoints too. That's why the heading changes. But not the pitch.

I have a POItest mission I can run too. I need to see if the wind has died down.

 

[BryanBTX]

Nice video.

So you are saying that for that mission you had gimbal pitch disabled and the camera was still executing those up and down aiming motions automatically?

I also noticed that in every waypoint towards the end every waypoint has a different altitude. Because the house is on the side of a small hill. That might be why you see the camera moving up and down.

 

[bsartist]

Litchi support says:

Litchi replied:


Hello,

1) Focus POI is continuous and happens even between 2 waypoints, not just at waypoints.
2) Disabled means what it means, Litchi won’t touch the gimbal if set to disabled.

Kind Regards,
Litchi

 

[dwallersv]

This is from the Litchi manual. The use of the word "keep" I think is what convinced me that dwallersv is correct about focus poi mode. It also implies that "disable" will cause Litchi not to aim the gimbal at all.

• Gimbal Pitch: Choose between "Disabled" where the gimbal pitch control will be manual, "Focus POI" where Litchi will automatically control the gimbal pitch to keep the selected POI in the center of the frame (blue markers), or "Interpolate" where you can specify the gimbal pitch angle at this waypoint. For "Interpolate" to work, the previous or next waypoint need to be set to "Interpolate" as well. Litchi will then automatically adjust the gimbal pitch angle to start and end at the specified angles, and smoothly transition while travelling between the two waypoints.

If I worded things poorly, I apologize. The other explanations here are consistent with my understanding, and what the manual says.

If you set the gimbal to "disabled", it will not be controlled automatically at all. Whatever tilt angle its at when the mission starts, it will keep that angle the entire mission -- UNLESS you change it manually while the mission is running from the controller wheel, or the tilt indicator in the Litchi display. Note that the gimbal angle setting in a waypoint set to "disabled" is grayed out and says "N/A".

"Interpolate" allows you to set the tilt angle for a waypoint as a parameter. Between any two adjacent waypoints with Interpolate, Litchi will smoothly change the gimbal angle from the setting in the first waypoint to the angle of the second. For example, two waypoints 300m apart, both set to interpolate, first angle is -90, next is 0. 150m between the waypoints gimbal angle will be at -45, pitching up toward 0. At 225m the angle will be -22.5.

"Focus POI" is just interpolate with Litchi handling setting the waypoint angles for you. It figures them out based on the waypoint position and altitude geometry relative to the POI position and altitude. Move anything (waypoint, POI) and Litchi will recalculate the gimbal angles and update them in the waypoint(s). However, once the mission flies, the operational execution of these waypoints from the standpoint of the gimbal angle is EXACTLY THE SAME AS INTERPOLATE.

Finally, how does one cause an abrupt change in gimbal angle? By having non-adjacent "interpolate" waypoints with set angles and a "default" manual waypoint in between. For example, if you have a 1 waypoint at interpolate -90, second at "disabled", third at interpolate -15, when the mission is flown the gimbal will be at -90 all the way from waypoint 1 to waypoint 3, and then pitch up to -15deg at the max speed the gimbal can move.

Hope this helps.

 

[dwallersv]

Gimbal pitch is the up and down aiming of the camera. You are referring to the yaw angle. On a P3S that is controlled by how the AC points. (Other aircraft may have gimbal yaw. But nonetheless the question here is pitch - which is up and down aiming. Not horizontal directional aim).

Good catch, and to amplify on this, the important concepts are Heading and Course.

Course is the direction the aircraft is moving. In a Litchi mission, it is the line between waypoints.

Heading is where the "front" of the aircraft is pointing. I fixed-wing craft, the two are usually the same when flying straight, and only diverge a little in turns.

For helicopters and multirotors, they can be completely independent.

 

[bsartist]

If I worded things poorly, I apologize. The other explanations here are consistent with my understanding, and what the manual says.

If you set the gimbal to "disabled", it will not be controlled automatically at all. Whatever tilt angle its at when the mission starts, it will keep that angle the entire mission -- UNLESS you change it manually while the mission is running from the controller wheel, or the tilt indicator in the Litchi display. Note that the gimbal angle setting in a waypoint set to "disabled" is grayed out and says "N/A".

"Interpolate" allows you to set the tilt angle for a waypoint as a parameter. Between any two adjacent waypoints with Interpolate, Litchi will smoothly change the gimbal angle from the setting in the first waypoint to the angle of the second. For example, two waypoints 300m apart, both set to interpolate, first angle is -90, next is 0. 150m between the waypoints gimbal angle will be at -45, pitching up toward 0. At 225m the angle will be -22.5.

"Focus POI" is just interpolate with Litchi handling setting the waypoint angles for you. It figures them out based on the waypoint position and altitude geometry relative to the POI position and altitude. Move anything (waypoint, POI) and Litchi will recalculate the gimbal angles and update them in the waypoint(s). However, once the mission flies, the operational execution of these waypoints from the standpoint of the gimbal angle is EXACTLY THE SAME AS INTERPOLATE.

Finally, how does one cause an abrupt change in gimbal angle? By having non-adjacent "interpolate" waypoints with set angles and a "default" manual waypoint in between. For example, if you have a 1 waypoint at interpolate -90, second at "disabled", third at interpolate -15, when the mission is flown the gimbal will be at -90 all the way from waypoint 1 to waypoint 3, and then pitch up to -15deg at the max speed the gimbal can move.

Hope this helps.

I found your initial explanation to be clear but thanks for writing this because there was another nugget in here that threw me a little. You are saying that once in flight, Interpolate and Focus POI behave the same. Which would bring me back to thinking that my use of interpolate, while not necessary (I could use focus poi instead) would still have the gimbal trained on the POI. When I read your first note I had convinced myself that in some cases interpolate could cause it to be a little off the POI between waypoints depending on some geometry that I haven't quite visualized but assumed. So you are saying the by definition and mathematically that there can never be a case where interpolation between two points (assuming the gimbal is aimed at POI at both points) fails to be spot on the POI?

 

[BryanBTX]

From the book.

"Interpolate" allows you to set the tilt angle for a waypoint as a parameter.


"Focus POI" is just interpolate with Litchi handling setting the waypoint angles for you.

 

[bsartist]

From the book.

"Interpolate" allows you to set the tilt angle for a waypoint as a parameter.


"Focus POI" is just interpolate with Litchi handling setting the waypoint angles for you.

Yes. I was hitting focus poi to lock in the gimbal angle then hitting interpolate. Sounds like dvwallers is saying that would still keep me focused on POI in between.

 

[BryanBTX]

I read those two as 1. interpolate you have to set it yourself (the angle). 2.The other it uses the settings of height and other stuff to do it for you. I think that's how it looks smooth.

I did read where it says IOS has custom settings also.

 

[dwallersv]

Yes. I was hitting focus poi to lock in the gimbal angle then hitting interpolate. Sounds like dvwallers is saying that would still keep me focused on POI in between.

If you use Focus POI first, and look at the heading angle and gimbal angle, then change to interpolate and set the heading and gimbal to the same angles as Focus POI automatically calculated for you, then when you are AT that waypoint the orientation of the camera will be exactly the same as it would have been if you left it as Focus POI. Further, the POI can be deleted from the mission, and THAT waypoint will still point right at the point in space where the POI was originally before you deleted it.

Perform this same task for a group of waypoints -- i.e. set a POI, set the 5 waypoints to "Focus POI", go to each individually, wriite down the heading and gimbal angles, change waypoint setting to Interpolate, set heading and gimbal to be the same as calculated by Litchi with Focus POI -- and camera behavior for those 5 waypoints will be exactly the same as if you'd simply left the POI on the map and the 5 waypoints as "Focus POI".

The firmware in the aircraft doesn't have a concept of POIs. Rather, it can be programmed to go to a particular lat/long at a particular altitude, point the heading in a particular direction and the gimbal at a particular angle.

That's all the aircraft knows about in terms of what gets uploaded to it. It doesn't have any clue how those angles were determined before they were uploaded to the aircraft.

The Focus POI and Interpolate settings function purely in the pre-planning phase. When the mission is flying, it's simply going from one location to another, and aiming the drone and gimbal at the specified angles that were uploaded.