Waypoint mode, drone won't keep straight

[thatswedishguy]

Hello friendly drone pilots!

I decided to try out waypoint mode the other day. I wanted to fly with the camera pointing straight down, recording video of a road while flying straight above it. I put one waypoint at one end of the road, and another at the opposite end. I chose gimbal angle -90° and to fly the course. The problem is that the drone was turned about 10° left the whole time, so the symmetry was way off for my intended video. I tried again, same result. I decided to input a specific heading instead and that worked, but I can not get the nose to point towards the next (and in this case last) waypoint.

I eventually just flew it manually because it was much quicker and easier, but for future projects where I want to keep a specific speed and heading waypoint mode would be great! What am I missing?

Compass and IMU's are calibrated and aircraft direction is shown correctly on the map, which in my first case was pointing off course...

 

[kilomikebravo]

Is it possible that your Mavic was simply "crabbing into the wind" to maintain course? The fact that heading hold worked seems to indicate that.

 

[thatswedishguy]

I guess it's possible but I would think that it should point to the selected point of it can do so when manually selecting a heading. Given that it's a multirotor it could crab in any direction while keeping the nose pointing forward.

I'll have to investigate further

 

[kilomikebravo]

TSG: Following a discreet heading is easy for the drone because it only has to use the compass. But, flying a magnetic COURSE takes more computing because the wind direction is typically variable in flight and the aircraft has to constantly tweak it's magnetic heading to hold that specific magnetic course.

I think what you want is to have the camera hold the POI regardless of crab but it seems as though Waypoints doesn't do this. As of this writing, I'm fairly sure that Litchi is still better than Go4 Waypoints but I'll let the Litchi experts comment on that.

 

[thatswedishguy]

But it still stayed on course with an assigned heading, so it could obviously do it. But if I choose to have it point to the next (and last of two) waypoint it won't work.

I'm curious about Litchi but I'm holding out for a while until I figure out if waypoint mode or ground station can get the job done. It's easiest to just fly manually but without a spotter I can't always do that and guarantee line of sight.

 

[kilomikebravo]

But it still stayed on course with an assigned heading, so it could obviously do it.

TSG: As I said earlier, I'm no expert on Waypoints but, I do know a thing or two about aviation and I think the issue is, you may not know the difference between "heading" and "course."

When you say it could obviously do it, I think what it did was merely hold the heading and the wind wasn't very strong making the difference between the aircraft mag heading and its mag course very small. As I mentioned, it's an easy task for the M2 to hold heading. But, when it has to try and hold a course, the problem becomes figuring out the drift. It would have to make constant minute adjustments to its heading in order to hold the mag course.

If I'm way off base, my apologies.

 

[thatswedishguy]

I am fully aware of the difference between heading and course. I'm a flight simmer at a somewhat serious level.

I may have used the wrong terms earlier due to sleep deprivation. I don't remember the terminology in DJI GO4 and I can't check without connecting to my aircraft. I think the terminology used was direction. Setting it told the drone in which direction to point the nose while staying on course. In the very same conditions setting the direction manually made the aircraft travel on course pointing towards the second waypoint.

Telling it to point in the direction of the course (towards waypoint no 2) had it off to the left by 10° or so. For the aircraft this should have been exactly the same direction, and yet it only did it right when told manually what degree it should point towards. I flew the same course both times in the same wind conditions.
I couldn't use a point of interest either, because that would have had it tilt the gimbal and I wanted it at -90° the whole time.

I hope Ground Station will be better, but I'm still waiting for my iPad mount so it'll be a while before I get a chance to try.

 

[kilomikebravo]

TSG: My apologies for the heading/course text. Now why the result is different if you manually select the "direction" is beyond me but it still seems like the drone is flying a course to maintain "direction" in the "auto" scenario and actually maintaining a heading when set manually.

Anyway, if you are able to determine the cause once you get your tablet mount, please let us know as I for one am quite interested since I DO plan to investigate Waypoints in the near future.