How much intestinal fortitude do you have with waypoints?

[happydays]

The reason I chose Litchi over autopilot is that Litchi completes a mission even if the signal is lost. For long range runs out over open countryside it is great as the signal could easily get dropped depending on terrain / tree cover etc.

 

[Dounin Front]

Any rising speed can be converted to two components: Horizontal speed and vertical speed. You got to use geometry concepts to do it. Once you separate out these components, check if both are within the limits of P3 discounting the effects of wind.

I suggest to Litchi developers to warn users if the computed components cross the set limit. Currently Litchi has no parameter for vertical speed limit. A good program should compute internal hidden values and should warn users if they cross limits.

Similarly I request Litchi dev to warn users if the ground clearance goes below a set clear value. Litchi should automatically compute along the route and warn users if needed.

I asked Litchi on their forum about the consequences of a user specifying impossible actions (See below) and after reading their answer it sounds like they may not have all that much control over their program and leave much up to the DJI SDK.

(From Litchi)
Hi,
Afraid I am not able to give you a definite answer as the code for this is in the DJI firmware. Do you have a specific example in mind? It seems to me that in order for 2) to happen, the mission would have to be pretty risky already.

On Mon, May 2, 2016 at 5:30 PM, Richard Faust <[email protected]> wrote:
I bring this question to our VC Tech from a thread in the Phantom Pilots forum for the definitive answer.

If a very steep climb is needed between waypoints to clear an obstacle and the pilot has selected a vertical distance that cannot be accomplished within the horizontal distance between the waypoints at the aircraft speed selected for the mission,

1. Will the aircraft correct by slowing down to accomplish the vertical distance within the horizontal distance?
2. crash into the obstacle because it is unable to achieve the vertical speed necessary to climb to the next WP altitude in the horizontal distance and speed specified?

 

[meissner58]

I bought Litchi for two reasons; The ability to pre-programme missions and the POI capability.

Both work fantastically well. I'm working on two projects currently; mapping the route of a canal (30 odd miles) from Lough Neagh to Carlingford Lough; and a study of a big oak tree that I'm orbiting every two weeks and stitching together to make a video clip of the changing of the four seasons.

Both are a doddle using Litch, but for ordinary flying I still prefer the Go app. On Saturday, I set the phantom off on a Litchi mission, furthest point was 2.5km away, go a quick rotate around, then curve smoothly back in to pick up the entry point of the canal. So off it goes, and gets out to the extreme point, does the wee circle and heads back. Great stuff, but then I got the warning 'SD card full, recording stopped'. Schoolboy error! Forgot to format the card before taking off. So I had to RTH and redo the mission. But it worked perfectly.

On one other section, I lost signal for about a minute as it went out of range / behind trees, but it just flew right back as programmed. No problem, but you do have to learn to trust the technology.

That's is the scary part for me! But I'm sure I will relax more eventually. Whenever I see "weak signal " I just about crap my pants. My biggest fear is losing it even with RTH. Never had it happen yet. Maybe I need to so I over come this . I remember being about 2.8 miles out and trying the RTH. Worked beautiful coming back . Climbing to 250ft and landing 3ft from where it took off. I was so impressed. These things still amaze me! Once I learn the video editing and way points etc I'm going to doing this so much more!

 

[Tenly]

The reason I chose Litchi over autopilot is that Litchi completes a mission even if the signal is lost. For long range runs out over open countryside it is great as the signal could easily get dropped depending on terrain / tree cover etc.

Autopilot now has the LCMC (lost connection mission completion) that they were lacking before - but for that to work (with both Litchi and Autopilot), they have to rely on the DJI SDK.

If you're not worried about a lost connection - Autopilot affords a much greater degree of control during a waypoint mission because they use their own flight controller. Being able to define focus points anywhere on the map is the big one for me. With Litchi/DJI Go- you are limited to using the waypoints themselves as your Focus points. Being able to place them anywhere gives a lot more control and can produce a smoother, better video. On the other hand - Litchi (reportedly) has more actions that can be performed at each waypoint.

For creating a cinematic sequence that can be shot/framed *exactly* the way you need it - you can't beat AutoPilot.

The only right answer here is to own both products. Each product is better than the other in certain areas. If you only own one of them, you aren't able to get the most out of your Phantom!

 

[Dounin Front]

Autopilot now has the LCMC (lost connection mission completion) that they were lacking before - but for that to work (with both Litchi and Autopilot), they have to rely on the DJI SDK.

If you're not worried about a lost connection - Autopilot affords a much greater degree of control during a waypoint mission because they use their own flight controller. Being able to define focus points anywhere on the map is the big one for me. With Litchi/DJI Go- you are limited to using the waypoints themselves as your Focus points. Being able to place them anywhere gives a lot more control and can produce a smoother, better video. On the other hand - Litchi (reportedly) has more actions that can be performed at each waypoint.

For creating a cinematic sequence that can be shot/framed *exactly* the way you need it - you can't beat AutoPilot.
The only right answer here is to own both products. Each product is better than the other in certain areas. If you only own one of them, you aren't able to get the most out of your Phantom!

I don't quite understand what you are saying about WP differences between Litchi and AutoPilot. With Litchi I can place all the POIs I want (only one can be used per WP, of course) - put them anywhere and drag them around and change the focus altitude. Choosing a curved path will smoothly transition the camera from one WP to the next. Is that different than Auto Pilot?

 

[n6vmo]

Yes, I agree. I flew a mission this past Sunday morning with a altitude of 16' and a speed of 12.1MPH. The mission required me to increase altitude to 131' to navigate over some power lines. In the attached picture, you can see WP 11 is where I needed to program the altitude for 131'. The distance from WP 10 @16' to WP 11 @ 131' is only 62' in horizontal distance. The P3 was able to overcome that vertical climb and get me over the power lines (red line in picture).
That's a climb of 61.67° or ~150% grade.


I am wondering if Litchi ignores the horizontal speed and places altitude as a higher priority. In other words, Litchi tells the craft to be at altitude no mater what the horizontal speed. It slows down in speed until it gets to the desired altitude. A question for the developer, unless someone know for sure.

Flight Data answers question.......

I just downloaded the flight data from Sunday's flight. The data shows that the P3 slowed from 12.1 MPH to about 7 MPH in order to gain 115' of altitude in just 62' of distance. So it appears that Litchi or the DJi firmware places priority on altitude over distance. See the attached picture. The red dots on the Map window and the Charts window is centered between WP 10 and WP 11.
The mission speed was set to 12.1 MPH, which it held throughout the flight, until I had to abruptly increase altitude to clear some power lines.

 

[alokbhargava]

Flight Data answers question.......

I just downloaded the flight data from Sunday's flight. The data shows that the P3 slowed from 12.1 MPH to about 7 MPH in order to gain 115' of altitude in just 62' of distance. So it appears that Litchi or the DJi firmware places priority on altitude over distance. See the attached picture. The red dots on the Map window and the Charts window is centered between WP 10 and WP 11.
The mission speed was set to 12.1 MPH, which it held throughout the flight, until I had to abruptly increase altitude to clear some power lines.


View attachment 52517
View attachment 52519

Litchi calculates the speed needed to follow set route subject to max limit set. Priority is to follow route. It will slow down or speed up to maintain the 3D route. Follows the set speed if it can follow the route.

 

[Tenly]

I don't quite understand what you are saying about WP differences between Litchi and AutoPilot. With Litchi I can place all the POIs I want (only one can be used per WP, of course) - put them anywhere and drag them around and change the focus altitude. Choosing a curved path will smoothly transition the camera from one WP to the next. Is that different than Auto Pilot?

Yes - different in a number of ways. In Autopilot, you can drop a focus point anywhere on the map - or you can have it focus on a moving person, or specify a direction angle relative to north or relative to the course that the Phantom is travelling. I'm not 100% sure what Litchi has for focus options but I believe you can only focus on waypoints themselves and maybe one arbitrary POI that is not a waypoint?

In any case, on the image below, the green teardrops are focus points. They do not have to be on the path the drone is travelling. Each focus point has a matching focus trigger (green circle) that can be placed anywhere on the path. Focus can shift immediately - or gradually between 2 focus points. Another difference with Autopilot is that you can specify an altitude for your Focus point - so for the Statue of Liberty - Litchi would focus on her feet whereas Autopilot could focus on the torch.

Using airspace objects, Autopilot can automatically maintain focus on a moving person! If you're trying to capture a sunrise or sunset - have the camera point to the east or the west. If you're flying alongside the shore and want to focus on the beach to your right - set the focus to a course offset of 90degrees!

You can switch between these focus strategies as many times as you want/need to in a single mission - but because many of the focus options are dynamic - and because you can change the focus anywhere along the flight path - it is impossible to upload all of that to the drone in advance of the mission! To make all of those features work, Autopilot has to be in constant communication with the drone. That's why they didn't do Lost Connection Mission Completion until now - when you use the LCMC feature - you lose all of the other cool things.

Does this make it any clearer? Here are a couple of screen shots from a waypoint mission I created to do a golf course flyover. You can see the focus points and triggers - and in one of them I have the Path Inspector open which tells me EVERYTHING about what the drone will be doing at that point! The direction it is pointing, traveling, camera facing, speed, altitude, etc.... The path inspector alone saves me hundreds of hours vs fluky missions, tweaking something minor and flying again.

(The green line is only showing because I clicked on the green circle on the path. It shows me which focus point the trigger is bound to)

 

[n6vmo]

Flight Data answers question.......

I just downloaded the flight data from Sunday's flight. The data shows that the P3 slowed from 12.1 MPH to about 7 MPH in order to gain 115' of altitude in just 62' of distance. So it appears that Litchi or the DJi firmware places priority on altitude over distance. See the attached picture. The red dots on the Map window and the Charts window is centered between WP 10 and WP 11.
The mission speed was set to 12.1 MPH, which it held throughout the flight, until I had to abruptly increase altitude to clear some power lines.


View attachment 52517
View attachment 52519

Here's the video with a data overlay. The maneuver takes place at the ~7:10 mark into the video.

 

[Dounin Front]

Yes - different in a number of ways. In Autopilot, you can drop a focus point anywhere on the map - or you can have it focus on a moving person, or specify a direction angle relative to north or relative to the course that the Phantom is travelling. I'm not 100% sure what Litchi has for focus options but I believe you can only focus on waypoints themselves and maybe one arbitrary POI that is not a waypoint?

Thanks, but it might be a bit too complicated for this operator. I guess it's a matter/mixture of what you want or need and what you're used to.
I suppose AP has a feature like Litchi's browser Hub where you can prepare or tweak your missions on another computer and retrieve them later.
Does AP display the actual ground elevation of each WP? I find that very helpful around here.

 

[matti]

Here's the video with a data overlay. The maneuver takes place at the ~7:10 mark into the video.

So it appears Litchi/DJI FW slows down the mission to climb over obstacles instead of hitting them, right? Good.

Dounin Front's question above was well phrased and to the point but Litchi's answer was corporate-like-speak:

"Afraid I am not able to give you a definite answer as the code for this is in the DJI firmware. Do you have a specific example in mind? It seems to me that in order for 2) to happen, the mission would have to be pretty risky already."

Litchi should have evaluated the worst & best case scenarios based on their tests. And then just say it really depends on how DJI FW behaves, but do leave some safety marging or be sorry.

 

[Tenly]

Thanks, but it might be a bit too complicated for this operator. I guess it's a matter/mixture of what you want or need and what you're used to.
I suppose AP has a feature like Litchi's browser Hub where you can prepare or tweak your missions on another computer and retrieve them later.
Does AP display the actual ground elevation of each WP? I find that very helpful around here.

No ground elevation data - sorry.

Autopilot does seem rather daunting at first look - but once you dive in and start using it, it becomes pretty clear, pretty quickly....and there are plenty of people on this forum (including engineers from the company that make Autopilot) that can help you understand anything that's not clear.

Having said that though - my advice to you would be to watch the AutoPilot tutorials on YouTube so you have an idea of everything it's capable of - but then just go ahead and keep using Litchi until you find a situation in which Litchi can't do what you want - and then consider giving AutoPilot a try!

 

[n6vmo]

Another example of how accurate a WP mission can be.
Altitude set to 16'...